From 1d97747665b993eb0c625c8d0a28e2d0c8e167a3 Mon Sep 17 00:00:00 2001
From: ryuukk <44361234+ryuukk@users.noreply.github.com>
Date: Wed, 14 Oct 2020 18:38:59 +0200
Subject: [PATCH 01/16] Pretty print Slices

This code is adapted from pixelherodev paste from IRC

I have added a new fmt option to handle printing slice values ``{v}`` or ``{V}``

While i think it can be made the default, i want your opinion about it

```zig
    var slicea = [0]u32{};
    var sliceb = [3]u32{ 1, 2, 3 };

    std.log.info("Content: {v}", .{slicea});
    std.log.info("Content: {v}", .{sliceb});
```

will print:

```
info: Content: []
info: Content: [1, 2, 3]
```

Question:

Should we drop ``{v}`` and make it the default behavior?
---
 lib/std/fmt.zig | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 803df7da94..8336324535 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -504,6 +504,18 @@ pub fn formatType(
                 }
                 if (ptr_info.child == u8) {
                     return formatText(value, fmt, options, writer);
+                } else if (fmt.len > 0 and ((fmt[0] == 'v') or (fmt[0] == 'V'))) {
+                    try format(writer, "[", .{});
+                    var i: usize = 0;
+                    for (value) |one| {
+                        if (i == value.len - 1) {
+                            try format(writer, "{}", .{one});
+                        } else{ 
+                            try format(writer, "{}, ", .{one});
+                        }
+                        i += 1;
+                    }
+                    return format(writer, "]", .{});
                 }
                 return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value.ptr) });
             },

From 5275280ede72fbc3eb702ff7f01fac07b306ca46 Mon Sep 17 00:00:00 2001
From: ryuukk <44361234+ryuukk@users.noreply.github.com>
Date: Wed, 14 Oct 2020 18:45:46 +0200
Subject: [PATCH 02/16] Formatting fix

---
 lib/std/fmt.zig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 8336324535..4d9a70cfdb 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -510,7 +510,7 @@ pub fn formatType(
                     for (value) |one| {
                         if (i == value.len - 1) {
                             try format(writer, "{}", .{one});
-                        } else{ 
+                        } else { 
                             try format(writer, "{}, ", .{one});
                         }
                         i += 1;

From 6f53653db17933fe2c8502d5bfc60857097b8bff Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 29 Oct 2020 22:22:25 +0100
Subject: [PATCH 03/16] std: Refactor the slice formatting code

Also fix the `*` specifier for more types, print an error message if we
can't show the value address.
---
 lib/std/fmt.zig | 71 ++++++++++++++++++++++++++++++++++---------------
 1 file changed, 50 insertions(+), 21 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 4d9a70cfdb..0a4a6a7328 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -367,6 +367,36 @@ pub fn format(
     }
 }
 
+pub fn formatAddress(value: anytype, options: FormatOptions, writer: anytype) @TypeOf(writer).Error!void {
+    const T = @TypeOf(value);
+
+    switch (@typeInfo(T)) {
+        .Pointer => |info| {
+            try writer.writeAll(@typeName(info.child) ++ "@");
+            if (info.size == .Slice)
+                try formatInt(@ptrToInt(value.ptr), 16, false, FormatOptions{}, writer)
+            else
+                try formatInt(@ptrToInt(value), 16, false, FormatOptions{}, writer);
+            return;
+        },
+        .Optional => |info| {
+            if (@typeInfo(info.child) == .Pointer) {
+                try writer.writeAll(@typeName(info.child) ++ "@");
+                try formatInt(@ptrToInt(value), 16, false, FormatOptions{}, writer);
+                return;
+            }
+        },
+        .Array => |info| {
+            try writer.writeAll(@typeName(info.child) ++ "@");
+            try formatInt(@ptrToInt(value), 16, false, FormatOptions{}, writer);
+            return;
+        },
+        else => {},
+    }
+
+    @compileError("Cannot format non-pointer type " ++ @typeName(T) ++ " with * specifier");
+}
+
 pub fn formatType(
     value: anytype,
     comptime fmt: []const u8,
@@ -375,10 +405,7 @@ pub fn formatType(
     max_depth: usize,
 ) @TypeOf(writer).Error!void {
     if (comptime std.mem.eql(u8, fmt, "*")) {
-        try writer.writeAll(@typeName(std.meta.Child(@TypeOf(value))));
-        try writer.writeAll("@");
-        try formatInt(@ptrToInt(value), 16, false, FormatOptions{}, writer);
-        return;
+        return formatAddress(value, options, writer);
     }
 
     const T = @TypeOf(value);
@@ -499,25 +526,18 @@ pub fn formatType(
                 return format(writer, "{}@{x}", .{ @typeName(@typeInfo(T).Pointer.child), @ptrToInt(value) });
             },
             .Slice => {
-                if (fmt.len > 0 and ((fmt[0] == 'x') or (fmt[0] == 'X'))) {
-                    return formatText(value, fmt, options, writer);
-                }
                 if (ptr_info.child == u8) {
                     return formatText(value, fmt, options, writer);
-                } else if (fmt.len > 0 and ((fmt[0] == 'v') or (fmt[0] == 'V'))) {
-                    try format(writer, "[", .{});
-                    var i: usize = 0;
-                    for (value) |one| {
-                        if (i == value.len - 1) {
-                            try format(writer, "{}", .{one});
-                        } else { 
-                            try format(writer, "{}, ", .{one});
-                        }
-                        i += 1;
-                    }
-                    return format(writer, "]", .{});
                 }
-                return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value.ptr) });
+
+                try writer.writeAll("[");
+                for (value) |elem, i| {
+                    try formatType(elem, fmt, options, writer, max_depth);
+                    if (i != value.len - 1) {
+                        try writer.writeAll(", ");
+                    }
+                }
+                try writer.writeAll("]");
             },
         },
         .Array => |info| {
@@ -1553,7 +1573,7 @@ test "slice" {
     {
         var runtime_zero: usize = 0;
         const value = @intToPtr([*]align(1) const []const u8, 0xdeadbeef)[runtime_zero..runtime_zero];
-        try testFmt("slice: []const u8@deadbeef\n", "slice: {}\n", .{value});
+        try testFmt("slice: []const u8@deadbeef\n", "slice: {*}\n", .{value});
     }
     {
         const null_term_slice: [:0]const u8 = "\x00hello\x00";
@@ -1562,6 +1582,15 @@ test "slice" {
 
     try testFmt("buf:  Test\n", "buf: {s:5}\n", .{"Test"});
     try testFmt("buf: Test\n Other text", "buf: {s}\n Other text", .{"Test"});
+
+    {
+        var int_slice = [_]u32{ 1, 4096, 391891, 1111111111 };
+        var runtime_zero: usize = 0;
+        try testFmt("int: [1, 4096, 391891, 1111111111]", "int: {}", .{int_slice[runtime_zero..]});
+        try testFmt("int: [1, 4096, 391891, 1111111111]", "int: {d}", .{int_slice[runtime_zero..]});
+        try testFmt("int: [1, 1000, 5fad3, 423a35c7]", "int: {x}", .{int_slice[runtime_zero..]});
+        try testFmt("int: [00001, 01000, 5fad3, 423a35c7]", "int: {x:0>5}", .{int_slice[runtime_zero..]});
+    }
 }
 
 test "escape non-printable" {

From 2b5e93fd3ea7ced934c7310ce68177738b1cdb81 Mon Sep 17 00:00:00 2001
From: data-man <datamanrb@gmail.com>
Date: Sat, 31 Oct 2020 15:12:05 +0100
Subject: [PATCH 04/16] Add formatting for arrays

---
 lib/std/fmt.zig | 50 ++++++++++++++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 0a4a6a7328..a858053c00 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -483,13 +483,13 @@ pub fn formatType(
                 try format(writer, "@{x}", .{@ptrToInt(&value)});
             }
         },
-        .Struct => |StructT| {
+        .Struct => |info| {
             try writer.writeAll(@typeName(T));
             if (max_depth == 0) {
                 return writer.writeAll("{ ... }");
             }
             try writer.writeAll("{");
-            inline for (StructT.fields) |f, i| {
+            inline for (info.fields) |f, i| {
                 if (i == 0) {
                     try writer.writeAll(" .");
                 } else {
@@ -526,10 +526,14 @@ pub fn formatType(
                 return format(writer, "{}@{x}", .{ @typeName(@typeInfo(T).Pointer.child), @ptrToInt(value) });
             },
             .Slice => {
-                if (ptr_info.child == u8) {
-                    return formatText(value, fmt, options, writer);
+                if (max_depth == 0) {
+                    return writer.writeAll("[ ... ]");
+                }
+                if (ptr_info.child == u8) {
+                    if (fmt.len == 0 or fmt[0] == 's' or fmt[0] == 'x' or fmt[0] == 'X') {
+                        return formatText(value, fmt, options, writer);
+                    }
                 }
-
                 try writer.writeAll("[");
                 for (value) |elem, i| {
                     try formatType(elem, fmt, options, writer, max_depth);
@@ -541,26 +545,29 @@ pub fn formatType(
             },
         },
         .Array => |info| {
-            const Slice = @Type(builtin.TypeInfo{
-                .Pointer = .{
-                    .size = .Slice,
-                    .is_const = true,
-                    .is_volatile = false,
-                    .is_allowzero = false,
-                    .alignment = @alignOf(info.child),
-                    .child = info.child,
-                    .sentinel = null,
-                },
-            });
-            return formatType(@as(Slice, &value), fmt, options, writer, max_depth);
+            if (max_depth == 0) {
+                return writer.writeAll("{ ... }");
+            }
+            if (info.child == u8) {
+                if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
+                    return formatText(&value, fmt, options, writer);
+                }
+            }
+            try writer.writeAll("{ ");
+            for (value) |elem, i| {
+                try formatType(elem, fmt, options, writer, max_depth - 1);
+                if (i < value.len - 1) {
+                    try writer.writeAll(", ");
+                }
+            }
+            try writer.writeAll(" }");
         },
-        .Vector => {
-            const len = @typeInfo(T).Vector.len;
+        .Vector => |info| {
             try writer.writeAll("{ ");
             var i: usize = 0;
-            while (i < len) : (i += 1) {
+            while (i < info.len) : (i += 1) {
                 try formatValue(value[i], fmt, options, writer);
-                if (i < len - 1) {
+                if (i < info.len - 1) {
                     try writer.writeAll(", ");
                 }
             }
@@ -1555,6 +1562,7 @@ test "array" {
         const value: [3]u8 = "abc".*;
         try testFmt("array: abc\n", "array: {}\n", .{value});
         try testFmt("array: abc\n", "array: {}\n", .{&value});
+        try testFmt("array: { 97, 98, 99 }\n", "array: {d}\n", .{value});
 
         var buf: [100]u8 = undefined;
         try testFmt(

From d4a8fc8b67bd2ae26b997ee201545cbb1eb3c15f Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Sat, 31 Oct 2020 15:16:59 +0100
Subject: [PATCH 05/16] Small cleanup

---
 lib/std/fmt.zig | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index a858053c00..c02a1cc1b8 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -463,12 +463,11 @@ pub fn formatType(
             try formatType(@enumToInt(value), fmt, options, writer, max_depth);
             try writer.writeAll(")");
         },
-        .Union => {
+        .Union => |info| {
             try writer.writeAll(@typeName(T));
             if (max_depth == 0) {
                 return writer.writeAll("{ ... }");
             }
-            const info = @typeInfo(T).Union;
             if (info.tag_type) |UnionTagType| {
                 try writer.writeAll("{ .");
                 try writer.writeAll(@tagName(@as(UnionTagType, value)));
@@ -507,30 +506,30 @@ pub fn formatType(
                     if (info.child == u8) {
                         return formatText(value, fmt, options, writer);
                     }
-                    return format(writer, "{}@{x}", .{ @typeName(@typeInfo(T).Pointer.child), @ptrToInt(value) });
+                    return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
                 },
                 .Enum, .Union, .Struct => {
                     return formatType(value.*, fmt, options, writer, max_depth);
                 },
-                else => return format(writer, "{}@{x}", .{ @typeName(@typeInfo(T).Pointer.child), @ptrToInt(value) }),
+                else => return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) }),
             },
             .Many, .C => {
                 if (ptr_info.sentinel) |sentinel| {
                     return formatType(mem.span(value), fmt, options, writer, max_depth);
                 }
                 if (ptr_info.child == u8) {
-                    if (fmt.len > 0 and fmt[0] == 's') {
+                    if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXzZ", fmt[0]) != null) {
                         return formatText(mem.span(value), fmt, options, writer);
                     }
                 }
-                return format(writer, "{}@{x}", .{ @typeName(@typeInfo(T).Pointer.child), @ptrToInt(value) });
+                return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
             },
             .Slice => {
                 if (max_depth == 0) {
                     return writer.writeAll("[ ... ]");
                 }
                 if (ptr_info.child == u8) {
-                    if (fmt.len == 0 or fmt[0] == 's' or fmt[0] == 'x' or fmt[0] == 'X') {
+                    if (fmt.len == 0 or comptime mem.indexOfScalar(u8, "sxXzZ", fmt[0]) != null) {
                         return formatText(value, fmt, options, writer);
                     }
                 }

From 5a06fdfa5525920810005e73eaa1b6e79a6472ca Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 19 Nov 2020 19:02:30 +0100
Subject: [PATCH 06/16] Use same brace pairs for arrays/slices/vectors

---
 lib/std/fmt.zig | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index c02a1cc1b8..466375e18e 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -518,7 +518,7 @@ pub fn formatType(
                     return formatType(mem.span(value), fmt, options, writer, max_depth);
                 }
                 if (ptr_info.child == u8) {
-                    if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXzZ", fmt[0]) != null) {
+                    if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
                         return formatText(mem.span(value), fmt, options, writer);
                     }
                 }
@@ -526,21 +526,21 @@ pub fn formatType(
             },
             .Slice => {
                 if (max_depth == 0) {
-                    return writer.writeAll("[ ... ]");
+                    return writer.writeAll("{ ... }");
                 }
                 if (ptr_info.child == u8) {
-                    if (fmt.len == 0 or comptime mem.indexOfScalar(u8, "sxXzZ", fmt[0]) != null) {
+                    if (fmt.len == 0 or comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
                         return formatText(value, fmt, options, writer);
                     }
                 }
-                try writer.writeAll("[");
+                try writer.writeAll("{ ");
                 for (value) |elem, i| {
                     try formatType(elem, fmt, options, writer, max_depth);
                     if (i != value.len - 1) {
                         try writer.writeAll(", ");
                     }
                 }
-                try writer.writeAll("]");
+                try writer.writeAll(" }");
             },
         },
         .Array => |info| {
@@ -1593,10 +1593,10 @@ test "slice" {
     {
         var int_slice = [_]u32{ 1, 4096, 391891, 1111111111 };
         var runtime_zero: usize = 0;
-        try testFmt("int: [1, 4096, 391891, 1111111111]", "int: {}", .{int_slice[runtime_zero..]});
-        try testFmt("int: [1, 4096, 391891, 1111111111]", "int: {d}", .{int_slice[runtime_zero..]});
-        try testFmt("int: [1, 1000, 5fad3, 423a35c7]", "int: {x}", .{int_slice[runtime_zero..]});
-        try testFmt("int: [00001, 01000, 5fad3, 423a35c7]", "int: {x:0>5}", .{int_slice[runtime_zero..]});
+        try testFmt("int: { 1, 4096, 391891, 1111111111 }", "int: {}", .{int_slice[runtime_zero..]});
+        try testFmt("int: { 1, 4096, 391891, 1111111111 }", "int: {d}", .{int_slice[runtime_zero..]});
+        try testFmt("int: { 1, 1000, 5fad3, 423a35c7 }", "int: {x}", .{int_slice[runtime_zero..]});
+        try testFmt("int: { 00001, 01000, 5fad3, 423a35c7 }", "int: {x:0>5}", .{int_slice[runtime_zero..]});
     }
 }
 

From dd973fb365dbbe11ce5beac8b4889bfab3fddc4d Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 09:48:12 +0100
Subject: [PATCH 07/16] std: Use {s} instead of {} when printing strings

---
 lib/std/SemanticVersion.zig                |   8 +-
 lib/std/array_list_sentineled.zig          | 229 +++++++++++++++
 lib/std/build.zig                          | 138 ++++-----
 lib/std/build/check_file.zig               |   4 +-
 lib/std/build/emit_raw.zig                 |   2 +-
 lib/std/build/run.zig                      |  26 +-
 lib/std/build/write_file.zig               |   4 +-
 lib/std/builtin.zig                        |  14 +-
 lib/std/c/tokenizer.zig                    |   2 +-
 lib/std/crypto/bcrypt.zig                  |   2 +-
 lib/std/debug.zig                          |  14 +-
 lib/std/fifo.zig                           |   2 +-
 lib/std/fmt.zig                            |  48 ++--
 lib/std/heap/general_purpose_allocator.zig |   8 +-
 lib/std/io/fixed_buffer_stream.zig         |   2 +-
 lib/std/json.zig                           |   8 +-
 lib/std/net.zig                            |   2 +-
 lib/std/os/windows.zig                     |   2 +-
 lib/std/process.zig                        |   2 +-
 lib/std/progress.zig                       | 310 +++++++++++++++++++++
 lib/std/special/test_runner.zig            |  16 +-
 lib/std/start.zig                          |   6 +-
 lib/std/target.zig                         |  12 +-
 lib/std/testing.zig                        |  15 +-
 lib/std/thread.zig                         |   6 +-
 lib/std/zig/ast.zig                        |  84 +++---
 lib/std/zig/cross_target.zig               |  10 +-
 lib/std/zig/parser_test.zig                |   2 +-
 lib/std/zig/render.zig                     |   2 +-
 lib/std/zig/system.zig                     |  16 +-
 lib/std/zig/tokenizer.zig                  |   4 +-
 test/stage1/behavior.zig                   |   2 +-
 32 files changed, 771 insertions(+), 231 deletions(-)
 create mode 100644 lib/std/array_list_sentineled.zig
 create mode 100644 lib/std/progress.zig

diff --git a/lib/std/SemanticVersion.zig b/lib/std/SemanticVersion.zig
index 74e515f9d1..eeb6916ad6 100644
--- a/lib/std/SemanticVersion.zig
+++ b/lib/std/SemanticVersion.zig
@@ -164,8 +164,8 @@ pub fn format(
 ) !void {
     if (fmt.len != 0) @compileError("Unknown format string: '" ++ fmt ++ "'");
     try std.fmt.format(out_stream, "{}.{}.{}", .{ self.major, self.minor, self.patch });
-    if (self.pre) |pre| try std.fmt.format(out_stream, "-{}", .{pre});
-    if (self.build) |build| try std.fmt.format(out_stream, "+{}", .{build});
+    if (self.pre) |pre| try std.fmt.format(out_stream, "-{s}", .{pre});
+    if (self.build) |build| try std.fmt.format(out_stream, "+{s}", .{build});
 }
 
 const expect = std.testing.expect;
@@ -287,9 +287,9 @@ fn testFmt(expected: []const u8, comptime template: []const u8, args: anytype) !
     if (std.mem.eql(u8, result, expected)) return;
 
     std.debug.warn("\n====== expected this output: =========\n", .{});
-    std.debug.warn("{}", .{expected});
+    std.debug.warn("{s}", .{expected});
     std.debug.warn("\n======== instead found this: =========\n", .{});
-    std.debug.warn("{}", .{result});
+    std.debug.warn("{s}", .{result});
     std.debug.warn("\n======================================\n", .{});
     return error.TestFailed;
 }
diff --git a/lib/std/array_list_sentineled.zig b/lib/std/array_list_sentineled.zig
new file mode 100644
index 0000000000..323b5eaaed
--- /dev/null
+++ b/lib/std/array_list_sentineled.zig
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+const std = @import("std.zig");
+const debug = std.debug;
+const mem = std.mem;
+const Allocator = mem.Allocator;
+const assert = debug.assert;
+const testing = std.testing;
+const ArrayList = std.ArrayList;
+
+/// A contiguous, growable list of items in memory, with a sentinel after them.
+/// The sentinel is maintained when appending, resizing, etc.
+/// If you do not need a sentinel, consider using `ArrayList` instead.
+pub fn ArrayListSentineled(comptime T: type, comptime sentinel: T) type {
+    return struct {
+        list: ArrayList(T),
+
+        const Self = @This();
+
+        /// Must deinitialize with deinit.
+        pub fn init(allocator: *Allocator, m: []const T) !Self {
+            var self = try initSize(allocator, m.len);
+            mem.copy(T, self.list.items, m);
+            return self;
+        }
+
+        /// Initialize memory to size bytes of undefined values.
+        /// Must deinitialize with deinit.
+        pub fn initSize(allocator: *Allocator, size: usize) !Self {
+            var self = initNull(allocator);
+            try self.resize(size);
+            return self;
+        }
+
+        /// Initialize with capacity to hold at least num bytes.
+        /// Must deinitialize with deinit.
+        pub fn initCapacity(allocator: *Allocator, num: usize) !Self {
+            var self = Self{ .list = try ArrayList(T).initCapacity(allocator, num + 1) };
+            self.list.appendAssumeCapacity(sentinel);
+            return self;
+        }
+
+        /// Must deinitialize with deinit.
+        /// None of the other operations are valid until you do one of these:
+        /// * `replaceContents`
+        /// * `resize`
+        pub fn initNull(allocator: *Allocator) Self {
+            return Self{ .list = ArrayList(T).init(allocator) };
+        }
+
+        /// Must deinitialize with deinit.
+        pub fn initFromBuffer(buffer: Self) !Self {
+            return Self.init(buffer.list.allocator, buffer.span());
+        }
+
+        /// Takes ownership of the passed in slice. The slice must have been
+        /// allocated with `allocator`.
+        /// Must deinitialize with deinit.
+        pub fn fromOwnedSlice(allocator: *Allocator, slice: []T) !Self {
+            var self = Self{ .list = ArrayList(T).fromOwnedSlice(allocator, slice) };
+            try self.list.append(sentinel);
+            return self;
+        }
+
+        /// The caller owns the returned memory. The list becomes null and is safe to `deinit`.
+        pub fn toOwnedSlice(self: *Self) [:sentinel]T {
+            const allocator = self.list.allocator;
+            const result = self.list.toOwnedSlice();
+            self.* = initNull(allocator);
+            return result[0 .. result.len - 1 :sentinel];
+        }
+
+        /// Only works when `T` is `u8`.
+        pub fn allocPrint(allocator: *Allocator, comptime format: []const u8, args: anytype) !Self {
+            const size = std.math.cast(usize, std.fmt.count(format, args)) catch |err| switch (err) {
+                error.Overflow => return error.OutOfMemory,
+            };
+            var self = try Self.initSize(allocator, size);
+            assert((std.fmt.bufPrint(self.list.items, format, args) catch unreachable).len == size);
+            return self;
+        }
+
+        pub fn deinit(self: *Self) void {
+            self.list.deinit();
+        }
+
+        pub fn span(self: anytype) @TypeOf(self.list.items[0..:sentinel]) {
+            return self.list.items[0..self.len() :sentinel];
+        }
+
+        pub fn shrink(self: *Self, new_len: usize) void {
+            assert(new_len <= self.len());
+            self.list.shrink(new_len + 1);
+            self.list.items[self.len()] = sentinel;
+        }
+
+        pub fn resize(self: *Self, new_len: usize) !void {
+            try self.list.resize(new_len + 1);
+            self.list.items[self.len()] = sentinel;
+        }
+
+        pub fn isNull(self: Self) bool {
+            return self.list.items.len == 0;
+        }
+
+        pub fn len(self: Self) usize {
+            return self.list.items.len - 1;
+        }
+
+        pub fn capacity(self: Self) usize {
+            return if (self.list.capacity > 0)
+                self.list.capacity - 1
+            else
+                0;
+        }
+
+        pub fn appendSlice(self: *Self, m: []const T) !void {
+            const old_len = self.len();
+            try self.resize(old_len + m.len);
+            mem.copy(T, self.list.items[old_len..], m);
+        }
+
+        pub fn append(self: *Self, byte: T) !void {
+            const old_len = self.len();
+            try self.resize(old_len + 1);
+            self.list.items[old_len] = byte;
+        }
+
+        pub fn eql(self: Self, m: []const T) bool {
+            return mem.eql(T, self.span(), m);
+        }
+
+        pub fn startsWith(self: Self, m: []const T) bool {
+            if (self.len() < m.len) return false;
+            return mem.eql(T, self.list.items[0..m.len], m);
+        }
+
+        pub fn endsWith(self: Self, m: []const T) bool {
+            const l = self.len();
+            if (l < m.len) return false;
+            const start = l - m.len;
+            return mem.eql(T, self.list.items[start..l], m);
+        }
+
+        pub fn replaceContents(self: *Self, m: []const T) !void {
+            try self.resize(m.len);
+            mem.copy(T, self.list.items, m);
+        }
+
+        /// Initializes an OutStream which will append to the list.
+        /// This function may be called only when `T` is `u8`.
+        pub fn outStream(self: *Self) std.io.OutStream(*Self, error{OutOfMemory}, appendWrite) {
+            return .{ .context = self };
+        }
+
+        /// Same as `append` except it returns the number of bytes written, which is always the same
+        /// as `m.len`. The purpose of this function existing is to match `std.io.OutStream` API.
+        /// This function may be called only when `T` is `u8`.
+        pub fn appendWrite(self: *Self, m: []const u8) !usize {
+            try self.appendSlice(m);
+            return m.len;
+        }
+    };
+}
+
+test "simple" {
+    var buf = try ArrayListSentineled(u8, 0).init(testing.allocator, "");
+    defer buf.deinit();
+
+    testing.expect(buf.len() == 0);
+    try buf.appendSlice("hello");
+    try buf.appendSlice(" ");
+    try buf.appendSlice("world");
+    testing.expect(buf.eql("hello world"));
+    testing.expect(mem.eql(u8, mem.spanZ(buf.span().ptr), buf.span()));
+
+    var buf2 = try ArrayListSentineled(u8, 0).initFromBuffer(buf);
+    defer buf2.deinit();
+    testing.expect(buf.eql(buf2.span()));
+
+    testing.expect(buf.startsWith("hell"));
+    testing.expect(buf.endsWith("orld"));
+
+    try buf2.resize(4);
+    testing.expect(buf.startsWith(buf2.span()));
+}
+
+test "initSize" {
+    var buf = try ArrayListSentineled(u8, 0).initSize(testing.allocator, 3);
+    defer buf.deinit();
+    testing.expect(buf.len() == 3);
+    try buf.appendSlice("hello");
+    testing.expect(mem.eql(u8, buf.span()[3..], "hello"));
+}
+
+test "initCapacity" {
+    var buf = try ArrayListSentineled(u8, 0).initCapacity(testing.allocator, 10);
+    defer buf.deinit();
+    testing.expect(buf.len() == 0);
+    testing.expect(buf.capacity() >= 10);
+    const old_cap = buf.capacity();
+    try buf.appendSlice("hello");
+    testing.expect(buf.len() == 5);
+    testing.expect(buf.capacity() == old_cap);
+    testing.expect(mem.eql(u8, buf.span(), "hello"));
+}
+
+test "print" {
+    var buf = try ArrayListSentineled(u8, 0).init(testing.allocator, "");
+    defer buf.deinit();
+
+    try buf.outStream().print("Hello {d} the {s}", .{ 2, "world" });
+    testing.expect(buf.eql("Hello 2 the world"));
+}
+
+test "outStream" {
+    var buffer = try ArrayListSentineled(u8, 0).initSize(testing.allocator, 0);
+    defer buffer.deinit();
+    const buf_stream = buffer.outStream();
+
+    const x: i32 = 42;
+    const y: i32 = 1234;
+    try buf_stream.print("x: {}\ny: {}\n", .{ x, y });
+
+    testing.expect(mem.eql(u8, buffer.span(), "x: 42\ny: 1234\n"));
+}
diff --git a/lib/std/build.zig b/lib/std/build.zig
index 3b6f8815bc..bd097c9414 100644
--- a/lib/std/build.zig
+++ b/lib/std/build.zig
@@ -294,7 +294,7 @@ pub const Builder = struct {
     /// To run an executable built with zig build, see `LibExeObjStep.run`.
     pub fn addSystemCommand(self: *Builder, argv: []const []const u8) *RunStep {
         assert(argv.len >= 1);
-        const run_step = RunStep.create(self, self.fmt("run {}", .{argv[0]}));
+        const run_step = RunStep.create(self, self.fmt("run {s}", .{argv[0]}));
         run_step.addArgs(argv);
         return run_step;
     }
@@ -409,7 +409,7 @@ pub const Builder = struct {
         for (self.installed_files.items) |installed_file| {
             const full_path = self.getInstallPath(installed_file.dir, installed_file.path);
             if (self.verbose) {
-                warn("rm {}\n", .{full_path});
+                warn("rm {s}\n", .{full_path});
             }
             fs.cwd().deleteTree(full_path) catch {};
         }
@@ -419,7 +419,7 @@ pub const Builder = struct {
 
     fn makeOneStep(self: *Builder, s: *Step) anyerror!void {
         if (s.loop_flag) {
-            warn("Dependency loop detected:\n  {}\n", .{s.name});
+            warn("Dependency loop detected:\n  {s}\n", .{s.name});
             return error.DependencyLoopDetected;
         }
         s.loop_flag = true;
@@ -427,7 +427,7 @@ pub const Builder = struct {
         for (s.dependencies.items) |dep| {
             self.makeOneStep(dep) catch |err| {
                 if (err == error.DependencyLoopDetected) {
-                    warn("  {}\n", .{s.name});
+                    warn("  {s}\n", .{s.name});
                 }
                 return err;
             };
@@ -444,7 +444,7 @@ pub const Builder = struct {
                 return &top_level_step.step;
             }
         }
-        warn("Cannot run step '{}' because it does not exist\n", .{name});
+        warn("Cannot run step '{s}' because it does not exist\n", .{name});
         return error.InvalidStepName;
     }
 
@@ -456,7 +456,7 @@ pub const Builder = struct {
             .description = description,
         };
         if ((self.available_options_map.fetchPut(name, available_option) catch unreachable) != null) {
-            panic("Option '{}' declared twice", .{name});
+            panic("Option '{s}' declared twice", .{name});
         }
         self.available_options_list.append(available_option) catch unreachable;
 
@@ -471,32 +471,32 @@ pub const Builder = struct {
                     } else if (mem.eql(u8, s, "false")) {
                         return false;
                     } else {
-                        warn("Expected -D{} to be a boolean, but received '{}'\n\n", .{ name, s });
+                        warn("Expected -D{s} to be a boolean, but received '{s}'\n\n", .{ name, s });
                         self.markInvalidUserInput();
                         return null;
                     }
                 },
                 .List => {
-                    warn("Expected -D{} to be a boolean, but received a list.\n\n", .{name});
+                    warn("Expected -D{s} to be a boolean, but received a list.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
             },
             .Int => switch (entry.value.value) {
                 .Flag => {
-                    warn("Expected -D{} to be an integer, but received a boolean.\n\n", .{name});
+                    warn("Expected -D{s} to be an integer, but received a boolean.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
                 .Scalar => |s| {
                     const n = std.fmt.parseInt(T, s, 10) catch |err| switch (err) {
                         error.Overflow => {
-                            warn("-D{} value {} cannot fit into type {}.\n\n", .{ name, s, @typeName(T) });
+                            warn("-D{s} value {} cannot fit into type {s}.\n\n", .{ name, s, @typeName(T) });
                             self.markInvalidUserInput();
                             return null;
                         },
                         else => {
-                            warn("Expected -D{} to be an integer of type {}.\n\n", .{ name, @typeName(T) });
+                            warn("Expected -D{s} to be an integer of type {s}.\n\n", .{ name, @typeName(T) });
                             self.markInvalidUserInput();
                             return null;
                         },
@@ -504,34 +504,34 @@ pub const Builder = struct {
                     return n;
                 },
                 .List => {
-                    warn("Expected -D{} to be an integer, but received a list.\n\n", .{name});
+                    warn("Expected -D{s} to be an integer, but received a list.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
             },
             .Float => switch (entry.value.value) {
                 .Flag => {
-                    warn("Expected -D{} to be a float, but received a boolean.\n\n", .{name});
+                    warn("Expected -D{s} to be a float, but received a boolean.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
                 .Scalar => |s| {
                     const n = std.fmt.parseFloat(T, s) catch |err| {
-                        warn("Expected -D{} to be a float of type {}.\n\n", .{ name, @typeName(T) });
+                        warn("Expected -D{s} to be a float of type {s}.\n\n", .{ name, @typeName(T) });
                         self.markInvalidUserInput();
                         return null;
                     };
                     return n;
                 },
                 .List => {
-                    warn("Expected -D{} to be a float, but received a list.\n\n", .{name});
+                    warn("Expected -D{s} to be a float, but received a list.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
             },
             .Enum => switch (entry.value.value) {
                 .Flag => {
-                    warn("Expected -D{} to be a string, but received a boolean.\n\n", .{name});
+                    warn("Expected -D{s} to be a string, but received a boolean.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
@@ -539,25 +539,25 @@ pub const Builder = struct {
                     if (std.meta.stringToEnum(T, s)) |enum_lit| {
                         return enum_lit;
                     } else {
-                        warn("Expected -D{} to be of type {}.\n\n", .{ name, @typeName(T) });
+                        warn("Expected -D{s} to be of type {s}.\n\n", .{ name, @typeName(T) });
                         self.markInvalidUserInput();
                         return null;
                     }
                 },
                 .List => {
-                    warn("Expected -D{} to be a string, but received a list.\n\n", .{name});
+                    warn("Expected -D{s} to be a string, but received a list.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
             },
             .String => switch (entry.value.value) {
                 .Flag => {
-                    warn("Expected -D{} to be a string, but received a boolean.\n\n", .{name});
+                    warn("Expected -D{s} to be a string, but received a boolean.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
                 .List => {
-                    warn("Expected -D{} to be a string, but received a list.\n\n", .{name});
+                    warn("Expected -D{s} to be a string, but received a list.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
@@ -565,7 +565,7 @@ pub const Builder = struct {
             },
             .List => switch (entry.value.value) {
                 .Flag => {
-                    warn("Expected -D{} to be a list, but received a boolean.\n\n", .{name});
+                    warn("Expected -D{s} to be a list, but received a boolean.\n\n", .{name});
                     self.markInvalidUserInput();
                     return null;
                 },
@@ -592,7 +592,7 @@ pub const Builder = struct {
         if (self.release_mode != null) {
             @panic("setPreferredReleaseMode must be called before standardReleaseOptions and may not be called twice");
         }
-        const description = self.fmt("Create a release build ({})", .{@tagName(mode)});
+        const description = self.fmt("Create a release build ({s})", .{@tagName(mode)});
         self.is_release = self.option(bool, "release", description) orelse false;
         self.release_mode = if (self.is_release) mode else builtin.Mode.Debug;
     }
@@ -646,12 +646,12 @@ pub const Builder = struct {
             .diagnostics = &diags,
         }) catch |err| switch (err) {
             error.UnknownCpuModel => {
-                warn("Unknown CPU: '{}'\nAvailable CPUs for architecture '{}':\n", .{
+                warn("Unknown CPU: '{s}'\nAvailable CPUs for architecture '{s}':\n", .{
                     diags.cpu_name.?,
                     @tagName(diags.arch.?),
                 });
                 for (diags.arch.?.allCpuModels()) |cpu| {
-                    warn(" {}\n", .{cpu.name});
+                    warn(" {s}\n", .{cpu.name});
                 }
                 warn("\n", .{});
                 self.markInvalidUserInput();
@@ -659,15 +659,15 @@ pub const Builder = struct {
             },
             error.UnknownCpuFeature => {
                 warn(
-                    \\Unknown CPU feature: '{}'
-                    \\Available CPU features for architecture '{}':
+                    \\Unknown CPU feature: '{s}'
+                    \\Available CPU features for architecture '{s}':
                     \\
                 , .{
                     diags.unknown_feature_name,
                     @tagName(diags.arch.?),
                 });
                 for (diags.arch.?.allFeaturesList()) |feature| {
-                    warn(" {}: {}\n", .{ feature.name, feature.description });
+                    warn(" {s}: {s}\n", .{ feature.name, feature.description });
                 }
                 warn("\n", .{});
                 self.markInvalidUserInput();
@@ -675,19 +675,19 @@ pub const Builder = struct {
             },
             error.UnknownOperatingSystem => {
                 warn(
-                    \\Unknown OS: '{}'
+                    \\Unknown OS: '{s}'
                     \\Available operating systems:
                     \\
                 , .{diags.os_name});
                 inline for (std.meta.fields(std.Target.Os.Tag)) |field| {
-                    warn(" {}\n", .{field.name});
+                    warn(" {s}\n", .{field.name});
                 }
                 warn("\n", .{});
                 self.markInvalidUserInput();
                 return args.default_target;
             },
             else => |e| {
-                warn("Unable to parse target '{}': {}\n\n", .{ triple, @errorName(e) });
+                warn("Unable to parse target '{}': {s}\n\n", .{ triple, @errorName(e) });
                 self.markInvalidUserInput();
                 return args.default_target;
             },
@@ -703,12 +703,12 @@ pub const Builder = struct {
                     break :whitelist_check;
                 }
             }
-            warn("Chosen target '{}' does not match one of the supported targets:\n", .{
+            warn("Chosen target '{s}' does not match one of the supported targets:\n", .{
                 selected_canonicalized_triple,
             });
             for (list) |t| {
                 const t_triple = t.zigTriple(self.allocator) catch unreachable;
-                warn(" {}\n", .{t_triple});
+                warn(" {s}\n", .{t_triple});
             }
             warn("\n", .{});
             self.markInvalidUserInput();
@@ -752,7 +752,7 @@ pub const Builder = struct {
                 }) catch unreachable;
             },
             UserValue.Flag => {
-                warn("Option '-D{}={}' conflicts with flag '-D{}'.\n", .{ name, value, name });
+                warn("Option '-D{s}={s}' conflicts with flag '-D{s}'.\n", .{ name, value, name });
                 return true;
             },
         }
@@ -773,11 +773,11 @@ pub const Builder = struct {
         // option already exists
         switch (gop.entry.value.value) {
             UserValue.Scalar => |s| {
-                warn("Flag '-D{}' conflicts with option '-D{}={}'.\n", .{ name, name, s });
+                warn("Flag '-D{s}' conflicts with option '-D{s}={s}'.\n", .{ name, name, s });
                 return true;
             },
             UserValue.List => {
-                warn("Flag '-D{}' conflicts with multiple options of the same name.\n", .{name});
+                warn("Flag '-D{s}' conflicts with multiple options of the same name.\n", .{name});
                 return true;
             },
             UserValue.Flag => {},
@@ -820,7 +820,7 @@ pub const Builder = struct {
         while (true) {
             const entry = it.next() orelse break;
             if (!entry.value.used) {
-                warn("Invalid option: -D{}\n\n", .{entry.key});
+                warn("Invalid option: -D{s}\n\n", .{entry.key});
                 self.markInvalidUserInput();
             }
         }
@@ -833,9 +833,9 @@ pub const Builder = struct {
     }
 
     fn printCmd(cwd: ?[]const u8, argv: []const []const u8) void {
-        if (cwd) |yes_cwd| warn("cd {} && ", .{yes_cwd});
+        if (cwd) |yes_cwd| warn("cd {s} && ", .{yes_cwd});
         for (argv) |arg| {
-            warn("{} ", .{arg});
+            warn("{s} ", .{arg});
         }
         warn("\n", .{});
     }
@@ -852,7 +852,7 @@ pub const Builder = struct {
         child.env_map = env_map;
 
         const term = child.spawnAndWait() catch |err| {
-            warn("Unable to spawn {}: {}\n", .{ argv[0], @errorName(err) });
+            warn("Unable to spawn {s}: {s}\n", .{ argv[0], @errorName(err) });
             return err;
         };
 
@@ -875,7 +875,7 @@ pub const Builder = struct {
 
     pub fn makePath(self: *Builder, path: []const u8) !void {
         fs.cwd().makePath(self.pathFromRoot(path)) catch |err| {
-            warn("Unable to create path {}: {}\n", .{ path, @errorName(err) });
+            warn("Unable to create path {s}: {s}\n", .{ path, @errorName(err) });
             return err;
         };
     }
@@ -959,7 +959,7 @@ pub const Builder = struct {
 
     pub fn updateFile(self: *Builder, source_path: []const u8, dest_path: []const u8) !void {
         if (self.verbose) {
-            warn("cp {} {} ", .{ source_path, dest_path });
+            warn("cp {s} {s} ", .{ source_path, dest_path });
         }
         const cwd = fs.cwd();
         const prev_status = try fs.Dir.updateFile(cwd, source_path, cwd, dest_path, .{});
@@ -988,7 +988,7 @@ pub const Builder = struct {
                 const full_path = try fs.path.join(self.allocator, &[_][]const u8{
                     search_prefix,
                     "bin",
-                    self.fmt("{}{}", .{ name, exe_extension }),
+                    self.fmt("{s}{s}", .{ name, exe_extension }),
                 });
                 return fs.realpathAlloc(self.allocator, full_path) catch continue;
             }
@@ -1002,7 +1002,7 @@ pub const Builder = struct {
                 while (it.next()) |path| {
                     const full_path = try fs.path.join(self.allocator, &[_][]const u8{
                         path,
-                        self.fmt("{}{}", .{ name, exe_extension }),
+                        self.fmt("{s}{s}", .{ name, exe_extension }),
                     });
                     return fs.realpathAlloc(self.allocator, full_path) catch continue;
                 }
@@ -1015,7 +1015,7 @@ pub const Builder = struct {
             for (paths) |path| {
                 const full_path = try fs.path.join(self.allocator, &[_][]const u8{
                     path,
-                    self.fmt("{}{}", .{ name, exe_extension }),
+                    self.fmt("{s}{s}", .{ name, exe_extension }),
                 });
                 return fs.realpathAlloc(self.allocator, full_path) catch continue;
             }
@@ -1070,19 +1070,19 @@ pub const Builder = struct {
         var code: u8 = undefined;
         return self.execAllowFail(argv, &code, .Inherit) catch |err| switch (err) {
             error.FileNotFound => {
-                if (src_step) |s| warn("{}...", .{s.name});
+                if (src_step) |s| warn("{s}...", .{s.name});
                 warn("Unable to spawn the following command: file not found\n", .{});
                 printCmd(null, argv);
                 std.os.exit(@truncate(u8, code));
             },
             error.ExitCodeFailure => {
-                if (src_step) |s| warn("{}...", .{s.name});
-                warn("The following command exited with error code {}:\n", .{code});
+                if (src_step) |s| warn("{s}...", .{s.name});
+                warn("The following command exited with error code {d}:\n", .{code});
                 printCmd(null, argv);
                 std.os.exit(@truncate(u8, code));
             },
             error.ProcessTerminated => {
-                if (src_step) |s| warn("{}...", .{s.name});
+                if (src_step) |s| warn("{s}...", .{s.name});
                 warn("The following command terminated unexpectedly:\n", .{});
                 printCmd(null, argv);
                 std.os.exit(@truncate(u8, code));
@@ -1405,7 +1405,7 @@ pub const LibExeObjStep = struct {
         ver: ?Version,
     ) LibExeObjStep {
         if (mem.indexOf(u8, name, "/") != null or mem.indexOf(u8, name, "\\") != null) {
-            panic("invalid name: '{}'. It looks like a file path, but it is supposed to be the library or application name.", .{name});
+            panic("invalid name: '{s}'. It looks like a file path, but it is supposed to be the library or application name.", .{name});
         }
         var self = LibExeObjStep{
             .strip = false,
@@ -1421,9 +1421,9 @@ pub const LibExeObjStep = struct {
             .step = Step.init(.LibExeObj, name, builder.allocator, make),
             .version = ver,
             .out_filename = undefined,
-            .out_h_filename = builder.fmt("{}.h", .{name}),
+            .out_h_filename = builder.fmt("{s}.h", .{name}),
             .out_lib_filename = undefined,
-            .out_pdb_filename = builder.fmt("{}.pdb", .{name}),
+            .out_pdb_filename = builder.fmt("{s}.pdb", .{name}),
             .major_only_filename = undefined,
             .name_only_filename = undefined,
             .packages = ArrayList(Pkg).init(builder.allocator),
@@ -1529,7 +1529,7 @@ pub const LibExeObjStep = struct {
         // It doesn't have to be native. We catch that if you actually try to run it.
         // Consider that this is declarative; the run step may not be run unless a user
         // option is supplied.
-        const run_step = RunStep.create(exe.builder, exe.builder.fmt("run {}", .{exe.step.name}));
+        const run_step = RunStep.create(exe.builder, exe.builder.fmt("run {s}", .{exe.step.name}));
         run_step.addArtifactArg(exe);
 
         if (exe.vcpkg_bin_path) |path| {
@@ -1680,7 +1680,7 @@ pub const LibExeObjStep = struct {
             } else if (mem.eql(u8, tok, "-pthread")) {
                 self.linkLibC();
             } else if (self.builder.verbose) {
-                warn("Ignoring pkg-config flag '{}'\n", .{tok});
+                warn("Ignoring pkg-config flag '{s}'\n", .{tok});
             }
         }
     }
@@ -1926,7 +1926,7 @@ pub const LibExeObjStep = struct {
             },
             else => {},
         }
-        out.print("pub const {z}: {} = {};\n", .{ name, @typeName(T), value }) catch unreachable;
+        out.print("pub const {z}: {s} = {};\n", .{ name, @typeName(T), value }) catch unreachable;
     }
 
     /// The value is the path in the cache dir.
@@ -2048,7 +2048,7 @@ pub const LibExeObjStep = struct {
         const builder = self.builder;
 
         if (self.root_src == null and self.link_objects.items.len == 0) {
-            warn("{}: linker needs 1 or more objects to link\n", .{self.step.name});
+            warn("{s}: linker needs 1 or more objects to link\n", .{self.step.name});
             return error.NeedAnObject;
         }
 
@@ -2156,12 +2156,12 @@ pub const LibExeObjStep = struct {
             // Render build artifact options at the last minute, now that the path is known.
             for (self.build_options_artifact_args.items) |item| {
                 const out = self.build_options_contents.writer();
-                out.print("pub const {}: []const u8 = \"{Z}\";\n", .{ item.name, item.artifact.getOutputPath() }) catch unreachable;
+                out.print("pub const {s}: []const u8 = \"{Z}\";\n", .{ item.name, item.artifact.getOutputPath() }) catch unreachable;
             }
 
             const build_options_file = try fs.path.join(
                 builder.allocator,
-                &[_][]const u8{ builder.cache_root, builder.fmt("{}_build_options.zig", .{self.name}) },
+                &[_][]const u8{ builder.cache_root, builder.fmt("{s}_build_options.zig", .{self.name}) },
             );
             const path_from_root = builder.pathFromRoot(build_options_file);
             try fs.cwd().writeFile(path_from_root, self.build_options_contents.items);
@@ -2294,16 +2294,16 @@ pub const LibExeObjStep = struct {
             } else {
                 var mcpu_buffer = std.ArrayList(u8).init(builder.allocator);
 
-                try mcpu_buffer.outStream().print("-mcpu={}", .{cross.cpu.model.name});
+                try mcpu_buffer.outStream().print("-mcpu={s}", .{cross.cpu.model.name});
 
                 for (all_features) |feature, i_usize| {
                     const i = @intCast(std.Target.Cpu.Feature.Set.Index, i_usize);
                     const in_cpu_set = populated_cpu_features.isEnabled(i);
                     const in_actual_set = cross.cpu.features.isEnabled(i);
                     if (in_cpu_set and !in_actual_set) {
-                        try mcpu_buffer.outStream().print("-{}", .{feature.name});
+                        try mcpu_buffer.outStream().print("-{s}", .{feature.name});
                     } else if (!in_cpu_set and in_actual_set) {
-                        try mcpu_buffer.outStream().print("+{}", .{feature.name});
+                        try mcpu_buffer.outStream().print("+{s}", .{feature.name});
                     }
                 }
 
@@ -2536,7 +2536,7 @@ pub const InstallArtifactStep = struct {
         const self = builder.allocator.create(Self) catch unreachable;
         self.* = Self{
             .builder = builder,
-            .step = Step.init(.InstallArtifact, builder.fmt("install {}", .{artifact.step.name}), builder.allocator, make),
+            .step = Step.init(.InstallArtifact, builder.fmt("install {s}", .{artifact.step.name}), builder.allocator, make),
             .artifact = artifact,
             .dest_dir = artifact.override_dest_dir orelse switch (artifact.kind) {
                 .Obj => unreachable,
@@ -2612,7 +2612,7 @@ pub const InstallFileStep = struct {
         builder.pushInstalledFile(dir, dest_rel_path);
         return InstallFileStep{
             .builder = builder,
-            .step = Step.init(.InstallFile, builder.fmt("install {}", .{src_path}), builder.allocator, make),
+            .step = Step.init(.InstallFile, builder.fmt("install {s}", .{src_path}), builder.allocator, make),
             .src_path = src_path,
             .dir = dir,
             .dest_rel_path = dest_rel_path,
@@ -2646,7 +2646,7 @@ pub const InstallDirStep = struct {
         builder.pushInstalledFile(options.install_dir, options.install_subdir);
         return InstallDirStep{
             .builder = builder,
-            .step = Step.init(.InstallDir, builder.fmt("install {}/", .{options.source_dir}), builder.allocator, make),
+            .step = Step.init(.InstallDir, builder.fmt("install {s}/", .{options.source_dir}), builder.allocator, make),
             .options = options,
         };
     }
@@ -2682,14 +2682,14 @@ pub const LogStep = struct {
     pub fn init(builder: *Builder, data: []const u8) LogStep {
         return LogStep{
             .builder = builder,
-            .step = Step.init(.Log, builder.fmt("log {}", .{data}), builder.allocator, make),
+            .step = Step.init(.Log, builder.fmt("log {s}", .{data}), builder.allocator, make),
             .data = data,
         };
     }
 
     fn make(step: *Step) anyerror!void {
         const self = @fieldParentPtr(LogStep, "step", step);
-        warn("{}", .{self.data});
+        warn("{s}", .{self.data});
     }
 };
 
@@ -2701,7 +2701,7 @@ pub const RemoveDirStep = struct {
     pub fn init(builder: *Builder, dir_path: []const u8) RemoveDirStep {
         return RemoveDirStep{
             .builder = builder,
-            .step = Step.init(.RemoveDir, builder.fmt("RemoveDir {}", .{dir_path}), builder.allocator, make),
+            .step = Step.init(.RemoveDir, builder.fmt("RemoveDir {s}", .{dir_path}), builder.allocator, make),
             .dir_path = dir_path,
         };
     }
@@ -2711,7 +2711,7 @@ pub const RemoveDirStep = struct {
 
         const full_path = self.builder.pathFromRoot(self.dir_path);
         fs.cwd().deleteTree(full_path) catch |err| {
-            warn("Unable to remove {}: {}\n", .{ full_path, @errorName(err) });
+            warn("Unable to remove {s}: {s}\n", .{ full_path, @errorName(err) });
             return err;
         };
     }
@@ -2799,7 +2799,7 @@ fn doAtomicSymLinks(allocator: *Allocator, output_path: []const u8, filename_maj
         &[_][]const u8{ out_dir, filename_major_only },
     ) catch unreachable;
     fs.atomicSymLink(allocator, out_basename, major_only_path) catch |err| {
-        warn("Unable to symlink {} -> {}\n", .{ major_only_path, out_basename });
+        warn("Unable to symlink {s} -> {s}\n", .{ major_only_path, out_basename });
         return err;
     };
     // sym link for libfoo.so to libfoo.so.1
@@ -2808,7 +2808,7 @@ fn doAtomicSymLinks(allocator: *Allocator, output_path: []const u8, filename_maj
         &[_][]const u8{ out_dir, filename_name_only },
     ) catch unreachable;
     fs.atomicSymLink(allocator, filename_major_only, name_only_path) catch |err| {
-        warn("Unable to symlink {} -> {}\n", .{ name_only_path, filename_major_only });
+        warn("Unable to symlink {s} -> {s}\n", .{ name_only_path, filename_major_only });
         return err;
     };
 }
diff --git a/lib/std/build/check_file.zig b/lib/std/build/check_file.zig
index 565ff0692a..31966fad52 100644
--- a/lib/std/build/check_file.zig
+++ b/lib/std/build/check_file.zig
@@ -45,9 +45,9 @@ pub const CheckFileStep = struct {
                 warn(
                     \\
                     \\========= Expected to find: ===================
-                    \\{}
+                    \\{s}
                     \\========= But file does not contain it: =======
-                    \\{}
+                    \\{s}
                     \\
                 , .{ expected_match, contents });
                 return error.TestFailed;
diff --git a/lib/std/build/emit_raw.zig b/lib/std/build/emit_raw.zig
index 66d44fc59f..3d2c6124c1 100644
--- a/lib/std/build/emit_raw.zig
+++ b/lib/std/build/emit_raw.zig
@@ -189,7 +189,7 @@ pub const InstallRawStep = struct {
     pub fn create(builder: *Builder, artifact: *LibExeObjStep, dest_filename: []const u8) *Self {
         const self = builder.allocator.create(Self) catch unreachable;
         self.* = Self{
-            .step = Step.init(.InstallRaw, builder.fmt("install raw binary {}", .{artifact.step.name}), builder.allocator, make),
+            .step = Step.init(.InstallRaw, builder.fmt("install raw binary {s}", .{artifact.step.name}), builder.allocator, make),
             .builder = builder,
             .artifact = artifact,
             .dest_dir = switch (artifact.kind) {
diff --git a/lib/std/build/run.zig b/lib/std/build/run.zig
index 18e05c2e01..36a4a1a843 100644
--- a/lib/std/build/run.zig
+++ b/lib/std/build/run.zig
@@ -116,7 +116,7 @@ pub const RunStep = struct {
         }
 
         if (prev_path) |pp| {
-            const new_path = self.builder.fmt("{}" ++ [1]u8{fs.path.delimiter} ++ "{}", .{ pp, search_path });
+            const new_path = self.builder.fmt("{s}" ++ [1]u8{fs.path.delimiter} ++ "{s}", .{ pp, search_path });
             env_map.set(key, new_path) catch unreachable;
         } else {
             env_map.set(key, search_path) catch unreachable;
@@ -189,7 +189,7 @@ pub const RunStep = struct {
         child.stderr_behavior = stdIoActionToBehavior(self.stderr_action);
 
         child.spawn() catch |err| {
-            warn("Unable to spawn {}: {}\n", .{ argv[0], @errorName(err) });
+            warn("Unable to spawn {s}: {s}\n", .{ argv[0], @errorName(err) });
             return err;
         };
 
@@ -216,7 +216,7 @@ pub const RunStep = struct {
         }
 
         const term = child.wait() catch |err| {
-            warn("Unable to spawn {}: {}\n", .{ argv[0], @errorName(err) });
+            warn("Unable to spawn {s}: {s}\n", .{ argv[0], @errorName(err) });
             return err;
         };
 
@@ -245,9 +245,9 @@ pub const RunStep = struct {
                     warn(
                         \\
                         \\========= Expected this stderr: =========
-                        \\{}
+                        \\{s}
                         \\========= But found: ====================
-                        \\{}
+                        \\{s}
                         \\
                     , .{ expected_bytes, stderr.? });
                     printCmd(cwd, argv);
@@ -259,9 +259,9 @@ pub const RunStep = struct {
                     warn(
                         \\
                         \\========= Expected to find in stderr: =========
-                        \\{}
+                        \\{s}
                         \\========= But stderr does not contain it: =====
-                        \\{}
+                        \\{s}
                         \\
                     , .{ match, stderr.? });
                     printCmd(cwd, argv);
@@ -277,9 +277,9 @@ pub const RunStep = struct {
                     warn(
                         \\
                         \\========= Expected this stdout: =========
-                        \\{}
+                        \\{s}
                         \\========= But found: ====================
-                        \\{}
+                        \\{s}
                         \\
                     , .{ expected_bytes, stdout.? });
                     printCmd(cwd, argv);
@@ -291,9 +291,9 @@ pub const RunStep = struct {
                     warn(
                         \\
                         \\========= Expected to find in stdout: =========
-                        \\{}
+                        \\{s}
                         \\========= But stdout does not contain it: =====
-                        \\{}
+                        \\{s}
                         \\
                     , .{ match, stdout.? });
                     printCmd(cwd, argv);
@@ -304,9 +304,9 @@ pub const RunStep = struct {
     }
 
     fn printCmd(cwd: ?[]const u8, argv: []const []const u8) void {
-        if (cwd) |yes_cwd| warn("cd {} && ", .{yes_cwd});
+        if (cwd) |yes_cwd| warn("cd {s} && ", .{yes_cwd});
         for (argv) |arg| {
-            warn("{} ", .{arg});
+            warn("{s} ", .{arg});
         }
         warn("\n", .{});
     }
diff --git a/lib/std/build/write_file.zig b/lib/std/build/write_file.zig
index 04b7268e81..bbe6ec5086 100644
--- a/lib/std/build/write_file.zig
+++ b/lib/std/build/write_file.zig
@@ -80,14 +80,14 @@ pub const WriteFileStep = struct {
         });
         // TODO replace with something like fs.makePathAndOpenDir
         fs.cwd().makePath(self.output_dir) catch |err| {
-            warn("unable to make path {}: {}\n", .{ self.output_dir, @errorName(err) });
+            warn("unable to make path {s}: {s}\n", .{ self.output_dir, @errorName(err) });
             return err;
         };
         var dir = try fs.cwd().openDir(self.output_dir, .{});
         defer dir.close();
         for (self.files.items) |file| {
             dir.writeFile(file.basename, file.bytes) catch |err| {
-                warn("unable to write {} into {}: {}\n", .{
+                warn("unable to write {s} into {s}: {s}\n", .{
                     file.basename,
                     self.output_dir,
                     @errorName(err),
diff --git a/lib/std/builtin.zig b/lib/std/builtin.zig
index fbc4a7cef5..c883e03ba9 100644
--- a/lib/std/builtin.zig
+++ b/lib/std/builtin.zig
@@ -67,12 +67,12 @@ pub const StackTrace = struct {
         var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
         defer arena.deinit();
         const debug_info = std.debug.getSelfDebugInfo() catch |err| {
-            return writer.print("\nUnable to print stack trace: Unable to open debug info: {}\n", .{@errorName(err)});
+            return writer.print("\nUnable to print stack trace: Unable to open debug info: {s}\n", .{@errorName(err)});
         };
         const tty_config = std.debug.detectTTYConfig();
         try writer.writeAll("\n");
         std.debug.writeStackTrace(self, writer, &arena.allocator, debug_info, tty_config) catch |err| {
-            try writer.print("Unable to print stack trace: {}\n", .{@errorName(err)});
+            try writer.print("Unable to print stack trace: {s}\n", .{@errorName(err)});
         };
         try writer.writeAll("\n");
     }
@@ -529,12 +529,12 @@ pub const Version = struct {
         if (fmt.len == 0) {
             if (self.patch == 0) {
                 if (self.minor == 0) {
-                    return std.fmt.format(out_stream, "{}", .{self.major});
+                    return std.fmt.format(out_stream, "{d}", .{self.major});
                 } else {
-                    return std.fmt.format(out_stream, "{}.{}", .{ self.major, self.minor });
+                    return std.fmt.format(out_stream, "{d}.{d}", .{ self.major, self.minor });
                 }
             } else {
-                return std.fmt.format(out_stream, "{}.{}.{}", .{ self.major, self.minor, self.patch });
+                return std.fmt.format(out_stream, "{d}.{d}.{d}", .{ self.major, self.minor, self.patch });
             }
         } else {
             @compileError("Unknown format string: '" ++ fmt ++ "'");
@@ -683,7 +683,7 @@ pub fn default_panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn
             }
         },
         .wasi => {
-            std.debug.warn("{}", .{msg});
+            std.debug.warn("{s}", .{msg});
             std.os.abort();
         },
         .uefi => {
@@ -692,7 +692,7 @@ pub fn default_panic(msg: []const u8, error_return_trace: ?*StackTrace) noreturn
         },
         else => {
             const first_trace_addr = @returnAddress();
-            std.debug.panicExtra(error_return_trace, first_trace_addr, "{}", .{msg});
+            std.debug.panicExtra(error_return_trace, first_trace_addr, "{s}", .{msg});
         },
     }
 }
diff --git a/lib/std/c/tokenizer.zig b/lib/std/c/tokenizer.zig
index 3fa3d1d6f8..aeb47fc4a0 100644
--- a/lib/std/c/tokenizer.zig
+++ b/lib/std/c/tokenizer.zig
@@ -1552,7 +1552,7 @@ fn expectTokens(source: []const u8, expected_tokens: []const Token.Id) void {
     for (expected_tokens) |expected_token_id| {
         const token = tokenizer.next();
         if (!std.meta.eql(token.id, expected_token_id)) {
-            std.debug.panic("expected {}, found {}\n", .{ @tagName(expected_token_id), @tagName(token.id) });
+            std.debug.panic("expected {s}, found {s}\n", .{ @tagName(expected_token_id), @tagName(token.id) });
         }
     }
     const last_token = tokenizer.next();
diff --git a/lib/std/crypto/bcrypt.zig b/lib/std/crypto/bcrypt.zig
index 554ba50c68..6d333c45cb 100644
--- a/lib/std/crypto/bcrypt.zig
+++ b/lib/std/crypto/bcrypt.zig
@@ -247,7 +247,7 @@ fn strHashInternal(password: []const u8, rounds_log: u6, salt: [salt_length]u8)
     Codec.encode(ct_str[0..], ct[0 .. ct.len - 1]);
 
     var s_buf: [hash_length]u8 = undefined;
-    const s = fmt.bufPrint(s_buf[0..], "$2b${}{}${}{}", .{ rounds_log / 10, rounds_log % 10, salt_str, ct_str }) catch unreachable;
+    const s = fmt.bufPrint(s_buf[0..], "$2b${d}{d}${s}{s}", .{ rounds_log / 10, rounds_log % 10, salt_str, ct_str }) catch unreachable;
     debug.assert(s.len == s_buf.len);
     return s_buf;
 }
diff --git a/lib/std/debug.zig b/lib/std/debug.zig
index 57a0e20d2e..073f68da5d 100644
--- a/lib/std/debug.zig
+++ b/lib/std/debug.zig
@@ -108,11 +108,11 @@ pub fn dumpCurrentStackTrace(start_addr: ?usize) void {
             return;
         }
         const debug_info = getSelfDebugInfo() catch |err| {
-            stderr.print("Unable to dump stack trace: Unable to open debug info: {}\n", .{@errorName(err)}) catch return;
+            stderr.print("Unable to dump stack trace: Unable to open debug info: {s}\n", .{@errorName(err)}) catch return;
             return;
         };
         writeCurrentStackTrace(stderr, debug_info, detectTTYConfig(), start_addr) catch |err| {
-            stderr.print("Unable to dump stack trace: {}\n", .{@errorName(err)}) catch return;
+            stderr.print("Unable to dump stack trace: {s}\n", .{@errorName(err)}) catch return;
             return;
         };
     }
@@ -129,7 +129,7 @@ pub fn dumpStackTraceFromBase(bp: usize, ip: usize) void {
             return;
         }
         const debug_info = getSelfDebugInfo() catch |err| {
-            stderr.print("Unable to dump stack trace: Unable to open debug info: {}\n", .{@errorName(err)}) catch return;
+            stderr.print("Unable to dump stack trace: Unable to open debug info: {s}\n", .{@errorName(err)}) catch return;
             return;
         };
         const tty_config = detectTTYConfig();
@@ -199,11 +199,11 @@ pub fn dumpStackTrace(stack_trace: builtin.StackTrace) void {
             return;
         }
         const debug_info = getSelfDebugInfo() catch |err| {
-            stderr.print("Unable to dump stack trace: Unable to open debug info: {}\n", .{@errorName(err)}) catch return;
+            stderr.print("Unable to dump stack trace: Unable to open debug info: {s}\n", .{@errorName(err)}) catch return;
             return;
         };
         writeStackTrace(stack_trace, stderr, getDebugInfoAllocator(), debug_info, detectTTYConfig()) catch |err| {
-            stderr.print("Unable to dump stack trace: {}\n", .{@errorName(err)}) catch return;
+            stderr.print("Unable to dump stack trace: {s}\n", .{@errorName(err)}) catch return;
             return;
         };
     }
@@ -611,7 +611,7 @@ fn printLineInfo(
         tty_config.setColor(out_stream, .White);
 
         if (line_info) |*li| {
-            try out_stream.print("{}:{}:{}", .{ li.file_name, li.line, li.column });
+            try out_stream.print("{s}:{d}:{d}", .{ li.file_name, li.line, li.column });
         } else {
             try out_stream.writeAll("???:?:?");
         }
@@ -619,7 +619,7 @@ fn printLineInfo(
         tty_config.setColor(out_stream, .Reset);
         try out_stream.writeAll(": ");
         tty_config.setColor(out_stream, .Dim);
-        try out_stream.print("0x{x} in {} ({})", .{ address, symbol_name, compile_unit_name });
+        try out_stream.print("0x{x} in {s} ({s})", .{ address, symbol_name, compile_unit_name });
         tty_config.setColor(out_stream, .Reset);
         try out_stream.writeAll("\n");
 
diff --git a/lib/std/fifo.zig b/lib/std/fifo.zig
index e9112c9178..788f8f1933 100644
--- a/lib/std/fifo.zig
+++ b/lib/std/fifo.zig
@@ -466,7 +466,7 @@ test "LinearFifo(u8, .Dynamic)" {
     fifo.shrink(0);
 
     {
-        try fifo.writer().print("{}, {}!", .{ "Hello", "World" });
+        try fifo.writer().print("{s}, {s}!", .{ "Hello", "World" });
         var result: [30]u8 = undefined;
         testing.expectEqualSlices(u8, "Hello, World!", result[0..fifo.read(&result)]);
         testing.expectEqual(@as(usize, 0), fifo.readableLength());
diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 466375e18e..7adee00928 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -506,12 +506,12 @@ pub fn formatType(
                     if (info.child == u8) {
                         return formatText(value, fmt, options, writer);
                     }
-                    return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
+                    return format(writer, "{s}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
                 },
                 .Enum, .Union, .Struct => {
                     return formatType(value.*, fmt, options, writer, max_depth);
                 },
-                else => return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) }),
+                else => return format(writer, "{s}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) }),
             },
             .Many, .C => {
                 if (ptr_info.sentinel) |sentinel| {
@@ -522,7 +522,7 @@ pub fn formatType(
                         return formatText(mem.span(value), fmt, options, writer);
                     }
                 }
-                return format(writer, "{}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
+                return format(writer, "{s}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
             },
             .Slice => {
                 if (max_depth == 0) {
@@ -573,7 +573,7 @@ pub fn formatType(
             try writer.writeAll(" }");
         },
         .Fn => {
-            return format(writer, "{}@{x}", .{ @typeName(T), @ptrToInt(value) });
+            return format(writer, "{s}@{x}", .{ @typeName(T), @ptrToInt(value) });
         },
         .Type => return formatBuf(@typeName(value), options, writer),
         .EnumLiteral => {
@@ -695,7 +695,7 @@ pub fn formatText(
     options: FormatOptions,
     writer: anytype,
 ) !void {
-    if (comptime std.mem.eql(u8, fmt, "s") or (fmt.len == 0)) {
+    if (comptime std.mem.eql(u8, fmt, "s")) {
         return formatBuf(bytes, options, writer);
     } else if (comptime (std.mem.eql(u8, fmt, "x") or std.mem.eql(u8, fmt, "X"))) {
         for (bytes) |c| {
@@ -1559,8 +1559,8 @@ test "buffer" {
 test "array" {
     {
         const value: [3]u8 = "abc".*;
-        try testFmt("array: abc\n", "array: {}\n", .{value});
-        try testFmt("array: abc\n", "array: {}\n", .{&value});
+        try testFmt("array: abc\n", "array: {s}\n", .{value});
+        try testFmt("array: abc\n", "array: {s}\n", .{&value});
         try testFmt("array: { 97, 98, 99 }\n", "array: {d}\n", .{value});
 
         var buf: [100]u8 = undefined;
@@ -1575,7 +1575,7 @@ test "array" {
 test "slice" {
     {
         const value: []const u8 = "abc";
-        try testFmt("slice: abc\n", "slice: {}\n", .{value});
+        try testFmt("slice: abc\n", "slice: {s}\n", .{value});
     }
     {
         var runtime_zero: usize = 0;
@@ -1902,9 +1902,9 @@ fn testFmt(expected: []const u8, comptime template: []const u8, args: anytype) !
     if (mem.eql(u8, result, expected)) return;
 
     std.debug.warn("\n====== expected this output: =========\n", .{});
-    std.debug.warn("{}", .{expected});
+    std.debug.warn("{s}", .{expected});
     std.debug.warn("\n======== instead found this: =========\n", .{});
-    std.debug.warn("{}", .{result});
+    std.debug.warn("{s}", .{result});
     std.debug.warn("\n======================================\n", .{});
     return error.TestFailed;
 }
@@ -2061,24 +2061,24 @@ test "vector" {
 }
 
 test "enum-literal" {
-    try testFmt(".hello_world", "{}", .{.hello_world});
+    try testFmt(".hello_world", "{s}", .{.hello_world});
 }
 
 test "padding" {
-    try testFmt("Simple", "{}", .{"Simple"});
+    try testFmt("Simple", "{s}", .{"Simple"});
     try testFmt("      true", "{:10}", .{true});
     try testFmt("      true", "{:>10}", .{true});
     try testFmt("======true", "{:=>10}", .{true});
     try testFmt("true======", "{:=<10}", .{true});
     try testFmt("   true   ", "{:^10}", .{true});
     try testFmt("===true===", "{:=^10}", .{true});
-    try testFmt("           Minimum width", "{:18} width", .{"Minimum"});
-    try testFmt("==================Filled", "{:=>24}", .{"Filled"});
-    try testFmt("        Centered        ", "{:^24}", .{"Centered"});
-    try testFmt("-", "{:-^1}", .{""});
-    try testFmt("==crêpe===", "{:=^10}", .{"crêpe"});
-    try testFmt("=====crêpe", "{:=>10}", .{"crêpe"});
-    try testFmt("crêpe=====", "{:=<10}", .{"crêpe"});
+    try testFmt("           Minimum width", "{s:18} width", .{"Minimum"});
+    try testFmt("==================Filled", "{s:=>24}", .{"Filled"});
+    try testFmt("        Centered        ", "{s:^24}", .{"Centered"});
+    try testFmt("-", "{s:-^1}", .{""});
+    try testFmt("==crêpe===", "{s:=^10}", .{"crêpe"});
+    try testFmt("=====crêpe", "{s:=>10}", .{"crêpe"});
+    try testFmt("crêpe=====", "{s:=<10}", .{"crêpe"});
 }
 
 test "decimal float padding" {
@@ -2107,15 +2107,15 @@ test "type" {
 }
 
 test "named arguments" {
-    try testFmt("hello world!", "{} world{c}", .{ "hello", '!' });
-    try testFmt("hello world!", "{[greeting]} world{[punctuation]c}", .{ .punctuation = '!', .greeting = "hello" });
-    try testFmt("hello world!", "{[1]} world{[0]c}", .{ '!', "hello" });
+    try testFmt("hello world!", "{s} world{c}", .{ "hello", '!' });
+    try testFmt("hello world!", "{[greeting]s} world{[punctuation]c}", .{ .punctuation = '!', .greeting = "hello" });
+    try testFmt("hello world!", "{[1]s} world{[0]c}", .{ '!', "hello" });
 }
 
 test "runtime width specifier" {
     var width: usize = 9;
-    try testFmt("~~hello~~", "{:~^[1]}", .{ "hello", width });
-    try testFmt("~~hello~~", "{:~^[width]}", .{ .string = "hello", .width = width });
+    try testFmt("~~hello~~", "{s:~^[1]}", .{ "hello", width });
+    try testFmt("~~hello~~", "{s:~^[width]}", .{ .string = "hello", .width = width });
 }
 
 test "runtime precision specifier" {
diff --git a/lib/std/heap/general_purpose_allocator.zig b/lib/std/heap/general_purpose_allocator.zig
index e7766f6445..415b206b6a 100644
--- a/lib/std/heap/general_purpose_allocator.zig
+++ b/lib/std/heap/general_purpose_allocator.zig
@@ -314,7 +314,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
                         if (is_used) {
                             const slot_index = @intCast(SlotIndex, used_bits_byte * 8 + bit_index);
                             const stack_trace = bucketStackTrace(bucket, size_class, slot_index, .alloc);
-                            log.err("Memory leak detected: {}", .{stack_trace});
+                            log.err("Memory leak detected: {s}", .{stack_trace});
                             leaks = true;
                         }
                         if (bit_index == math.maxInt(u3))
@@ -342,7 +342,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
             }
             var it = self.large_allocations.iterator();
             while (it.next()) |large_alloc| {
-                log.err("Memory leak detected: {}", .{large_alloc.value.getStackTrace()});
+                log.err("Memory leak detected: {s}", .{large_alloc.value.getStackTrace()});
                 leaks = true;
             }
             return leaks;
@@ -443,7 +443,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
                     .index = 0,
                 };
                 std.debug.captureStackTrace(ret_addr, &free_stack_trace);
-                log.err("Allocation size {} bytes does not match free size {}. Allocation: {} Free: {}", .{
+                log.err("Allocation size {d} bytes does not match free size {d}. Allocation: {s} Free: {s}", .{
                     entry.value.bytes.len,
                     old_mem.len,
                     entry.value.getStackTrace(),
@@ -526,7 +526,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
                         .index = 0,
                     };
                     std.debug.captureStackTrace(ret_addr, &second_free_stack_trace);
-                    log.err("Double free detected. Allocation: {} First free: {} Second free: {}", .{
+                    log.err("Double free detected. Allocation: {s} First free: {s} Second free: {s}", .{
                         alloc_stack_trace,
                         free_stack_trace,
                         second_free_stack_trace,
diff --git a/lib/std/io/fixed_buffer_stream.zig b/lib/std/io/fixed_buffer_stream.zig
index e698ce061e..b36949e538 100644
--- a/lib/std/io/fixed_buffer_stream.zig
+++ b/lib/std/io/fixed_buffer_stream.zig
@@ -147,7 +147,7 @@ test "FixedBufferStream output" {
     var fbs = fixedBufferStream(&buf);
     const stream = fbs.writer();
 
-    try stream.print("{}{}!", .{ "Hello", "World" });
+    try stream.print("{s}{s}!", .{ "Hello", "World" });
     testing.expectEqualSlices(u8, "HelloWorld!", fbs.getWritten());
 }
 
diff --git a/lib/std/json.zig b/lib/std/json.zig
index e412676fa3..f5be3a2094 100644
--- a/lib/std/json.zig
+++ b/lib/std/json.zig
@@ -2642,9 +2642,9 @@ fn teststringify(expected: []const u8, value: anytype, options: StringifyOptions
             if (self.expected_remaining.len < bytes.len) {
                 std.debug.warn(
                     \\====== expected this output: =========
-                    \\{}
+                    \\{s}
                     \\======== instead found this: =========
-                    \\{}
+                    \\{s}
                     \\======================================
                 , .{
                     self.expected_remaining,
@@ -2655,9 +2655,9 @@ fn teststringify(expected: []const u8, value: anytype, options: StringifyOptions
             if (!mem.eql(u8, self.expected_remaining[0..bytes.len], bytes)) {
                 std.debug.warn(
                     \\====== expected this output: =========
-                    \\{}
+                    \\{s}
                     \\======== instead found this: =========
-                    \\{}
+                    \\{s}
                     \\======================================
                 , .{
                     self.expected_remaining[0..bytes.len],
diff --git a/lib/std/net.zig b/lib/std/net.zig
index 5b17714fae..b8f48b2020 100644
--- a/lib/std/net.zig
+++ b/lib/std/net.zig
@@ -154,7 +154,7 @@ pub const Address = extern union {
                     unreachable;
                 }
 
-                try std.fmt.format(out_stream, "{}", .{&self.un.path});
+                try std.fmt.format(out_stream, "{s}", .{&self.un.path});
             },
             else => unreachable,
         }
diff --git a/lib/std/os/windows.zig b/lib/std/os/windows.zig
index 40271cdc38..1c6e5202a3 100644
--- a/lib/std/os/windows.zig
+++ b/lib/std/os/windows.zig
@@ -1618,7 +1618,7 @@ pub fn unexpectedError(err: Win32Error) std.os.UnexpectedError {
             null,
         );
         _ = std.unicode.utf16leToUtf8(&buf_u8, buf_u16[0..len]) catch unreachable;
-        std.debug.warn("error.Unexpected: GetLastError({}): {}\n", .{ @enumToInt(err), buf_u8[0..len] });
+        std.debug.warn("error.Unexpected: GetLastError({}): {s}\n", .{ @enumToInt(err), buf_u8[0..len] });
         std.debug.dumpCurrentStackTrace(null);
     }
     return error.Unexpected;
diff --git a/lib/std/process.zig b/lib/std/process.zig
index 3f944f10b6..3529bf52cb 100644
--- a/lib/std/process.zig
+++ b/lib/std/process.zig
@@ -596,7 +596,7 @@ fn testWindowsCmdLine(input_cmd_line: [*]const u16, expected_args: []const []con
     for (expected_args) |expected_arg| {
         const arg = it.next(std.testing.allocator).? catch unreachable;
         defer std.testing.allocator.free(arg);
-        testing.expectEqualSlices(u8, expected_arg, arg);
+        testing.expectEqualStrings(expected_arg, arg);
     }
     testing.expect(it.next(std.testing.allocator) == null);
 }
diff --git a/lib/std/progress.zig b/lib/std/progress.zig
new file mode 100644
index 0000000000..474ed050aa
--- /dev/null
+++ b/lib/std/progress.zig
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2020 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+const std = @import("std");
+const windows = std.os.windows;
+const testing = std.testing;
+const assert = std.debug.assert;
+
+/// This API is non-allocating and non-fallible. The tradeoff is that users of
+/// this API must provide the storage for each `Progress.Node`.
+/// Initialize the struct directly, overriding these fields as desired:
+/// * `refresh_rate_ms`
+/// * `initial_delay_ms`
+pub const Progress = struct {
+    /// `null` if the current node (and its children) should
+    /// not print on update()
+    terminal: ?std.fs.File = undefined,
+
+    /// Whether the terminal supports ANSI escape codes.
+    supports_ansi_escape_codes: bool = false,
+
+    root: Node = undefined,
+
+    /// Keeps track of how much time has passed since the beginning.
+    /// Used to compare with `initial_delay_ms` and `refresh_rate_ms`.
+    timer: std.time.Timer = undefined,
+
+    /// When the previous refresh was written to the terminal.
+    /// Used to compare with `refresh_rate_ms`.
+    prev_refresh_timestamp: u64 = undefined,
+
+    /// This buffer represents the maximum number of bytes written to the terminal
+    /// with each refresh.
+    output_buffer: [100]u8 = undefined,
+
+    /// How many nanoseconds between writing updates to the terminal.
+    refresh_rate_ns: u64 = 50 * std.time.ns_per_ms,
+
+    /// How many nanoseconds to keep the output hidden
+    initial_delay_ns: u64 = 500 * std.time.ns_per_ms,
+
+    done: bool = true,
+
+    /// Keeps track of how many columns in the terminal have been output, so that
+    /// we can move the cursor back later.
+    columns_written: usize = undefined,
+
+    /// Represents one unit of progress. Each node can have children nodes, or
+    /// one can use integers with `update`.
+    pub const Node = struct {
+        context: *Progress,
+        parent: ?*Node,
+        completed_items: usize,
+        name: []const u8,
+        recently_updated_child: ?*Node = null,
+
+        /// This field may be updated freely.
+        estimated_total_items: ?usize,
+
+        /// Create a new child progress node.
+        /// Call `Node.end` when done.
+        /// TODO solve https://github.com/ziglang/zig/issues/2765 and then change this
+        /// API to set `self.parent.recently_updated_child` with the return value.
+        /// Until that is fixed you probably want to call `activate` on the return value.
+        pub fn start(self: *Node, name: []const u8, estimated_total_items: ?usize) Node {
+            return Node{
+                .context = self.context,
+                .parent = self,
+                .completed_items = 0,
+                .name = name,
+                .estimated_total_items = estimated_total_items,
+            };
+        }
+
+        /// This is the same as calling `start` and then `end` on the returned `Node`.
+        pub fn completeOne(self: *Node) void {
+            if (self.parent) |parent| parent.recently_updated_child = self;
+            self.completed_items += 1;
+            self.context.maybeRefresh();
+        }
+
+        pub fn end(self: *Node) void {
+            self.context.maybeRefresh();
+            if (self.parent) |parent| {
+                if (parent.recently_updated_child) |parent_child| {
+                    if (parent_child == self) {
+                        parent.recently_updated_child = null;
+                    }
+                }
+                parent.completeOne();
+            } else {
+                self.context.done = true;
+                self.context.refresh();
+            }
+        }
+
+        /// Tell the parent node that this node is actively being worked on.
+        pub fn activate(self: *Node) void {
+            if (self.parent) |parent| parent.recently_updated_child = self;
+        }
+    };
+
+    /// Create a new progress node.
+    /// Call `Node.end` when done.
+    /// TODO solve https://github.com/ziglang/zig/issues/2765 and then change this
+    /// API to return Progress rather than accept it as a parameter.
+    pub fn start(self: *Progress, name: []const u8, estimated_total_items: ?usize) !*Node {
+        const stderr = std.io.getStdErr();
+        self.terminal = null;
+        if (stderr.supportsAnsiEscapeCodes()) {
+            self.terminal = stderr;
+            self.supports_ansi_escape_codes = true;
+        } else if (std.builtin.os.tag == .windows and stderr.isTty()) {
+            self.terminal = stderr;
+        }
+        self.root = Node{
+            .context = self,
+            .parent = null,
+            .completed_items = 0,
+            .name = name,
+            .estimated_total_items = estimated_total_items,
+        };
+        self.columns_written = 0;
+        self.prev_refresh_timestamp = 0;
+        self.timer = try std.time.Timer.start();
+        self.done = false;
+        return &self.root;
+    }
+
+    /// Updates the terminal if enough time has passed since last update.
+    pub fn maybeRefresh(self: *Progress) void {
+        const now = self.timer.read();
+        if (now < self.initial_delay_ns) return;
+        if (now - self.prev_refresh_timestamp < self.refresh_rate_ns) return;
+        self.refresh();
+    }
+
+    /// Updates the terminal and resets `self.next_refresh_timestamp`.
+    pub fn refresh(self: *Progress) void {
+        const file = self.terminal orelse return;
+
+        const prev_columns_written = self.columns_written;
+        var end: usize = 0;
+        if (self.columns_written > 0) {
+            // restore the cursor position by moving the cursor
+            // `columns_written` cells to the left, then clear the rest of the
+            // line
+            if (self.supports_ansi_escape_codes) {
+                end += (std.fmt.bufPrint(self.output_buffer[end..], "\x1b[{d}D", .{self.columns_written}) catch unreachable).len;
+                end += (std.fmt.bufPrint(self.output_buffer[end..], "\x1b[0K", .{}) catch unreachable).len;
+            } else if (std.builtin.os.tag == .windows) winapi: {
+                var info: windows.CONSOLE_SCREEN_BUFFER_INFO = undefined;
+                if (windows.kernel32.GetConsoleScreenBufferInfo(file.handle, &info) != windows.TRUE)
+                    unreachable;
+
+                var cursor_pos = windows.COORD{
+                    .X = info.dwCursorPosition.X - @intCast(windows.SHORT, self.columns_written),
+                    .Y = info.dwCursorPosition.Y,
+                };
+
+                if (cursor_pos.X < 0)
+                    cursor_pos.X = 0;
+
+                const fill_chars = @intCast(windows.DWORD, info.dwSize.X - cursor_pos.X);
+
+                var written: windows.DWORD = undefined;
+                if (windows.kernel32.FillConsoleOutputAttribute(
+                    file.handle,
+                    info.wAttributes,
+                    fill_chars,
+                    cursor_pos,
+                    &written,
+                ) != windows.TRUE) {
+                    // Stop trying to write to this file.
+                    self.terminal = null;
+                    break :winapi;
+                }
+                if (windows.kernel32.FillConsoleOutputCharacterA(
+                    file.handle,
+                    ' ',
+                    fill_chars,
+                    cursor_pos,
+                    &written,
+                ) != windows.TRUE) unreachable;
+
+                if (windows.kernel32.SetConsoleCursorPosition(file.handle, cursor_pos) != windows.TRUE)
+                    unreachable;
+            } else unreachable;
+
+            self.columns_written = 0;
+        }
+
+        if (!self.done) {
+            var need_ellipse = false;
+            var maybe_node: ?*Node = &self.root;
+            while (maybe_node) |node| {
+                if (need_ellipse) {
+                    self.bufWrite(&end, "... ", .{});
+                }
+                need_ellipse = false;
+                if (node.name.len != 0 or node.estimated_total_items != null) {
+                    if (node.name.len != 0) {
+                        self.bufWrite(&end, "{s}", .{node.name});
+                        need_ellipse = true;
+                    }
+                    if (node.estimated_total_items) |total| {
+                        if (need_ellipse) self.bufWrite(&end, " ", .{});
+                        self.bufWrite(&end, "[{d}/{d}] ", .{ node.completed_items + 1, total });
+                        need_ellipse = false;
+                    } else if (node.completed_items != 0) {
+                        if (need_ellipse) self.bufWrite(&end, " ", .{});
+                        self.bufWrite(&end, "[{d}] ", .{node.completed_items + 1});
+                        need_ellipse = false;
+                    }
+                }
+                maybe_node = node.recently_updated_child;
+            }
+            if (need_ellipse) {
+                self.bufWrite(&end, "... ", .{});
+            }
+        }
+
+        _ = file.write(self.output_buffer[0..end]) catch |e| {
+            // Stop trying to write to this file once it errors.
+            self.terminal = null;
+        };
+        self.prev_refresh_timestamp = self.timer.read();
+    }
+
+    pub fn log(self: *Progress, comptime format: []const u8, args: anytype) void {
+        const file = self.terminal orelse return;
+        self.refresh();
+        file.outStream().print(format, args) catch {
+            self.terminal = null;
+            return;
+        };
+        self.columns_written = 0;
+    }
+
+    fn bufWrite(self: *Progress, end: *usize, comptime format: []const u8, args: anytype) void {
+        if (std.fmt.bufPrint(self.output_buffer[end.*..], format, args)) |written| {
+            const amt = written.len;
+            end.* += amt;
+            self.columns_written += amt;
+        } else |err| switch (err) {
+            error.NoSpaceLeft => {
+                self.columns_written += self.output_buffer.len - end.*;
+                end.* = self.output_buffer.len;
+            },
+        }
+        const bytes_needed_for_esc_codes_at_end = if (std.builtin.os.tag == .windows) 0 else 11;
+        const max_end = self.output_buffer.len - bytes_needed_for_esc_codes_at_end;
+        if (end.* > max_end) {
+            const suffix = "... ";
+            self.columns_written = self.columns_written - (end.* - max_end) + suffix.len;
+            std.mem.copy(u8, self.output_buffer[max_end..], suffix);
+            end.* = max_end + suffix.len;
+        }
+    }
+};
+
+test "basic functionality" {
+    var disable = true;
+    if (disable) {
+        // This test is disabled because it uses time.sleep() and is therefore slow. It also
+        // prints bogus progress data to stderr.
+        return error.SkipZigTest;
+    }
+    var progress = Progress{};
+    const root_node = try progress.start("", 100);
+    defer root_node.end();
+
+    const sub_task_names = [_][]const u8{
+        "reticulating splines",
+        "adjusting shoes",
+        "climbing towers",
+        "pouring juice",
+    };
+    var next_sub_task: usize = 0;
+
+    var i: usize = 0;
+    while (i < 100) : (i += 1) {
+        var node = root_node.start(sub_task_names[next_sub_task], 5);
+        node.activate();
+        next_sub_task = (next_sub_task + 1) % sub_task_names.len;
+
+        node.completeOne();
+        std.time.sleep(5 * std.time.ns_per_ms);
+        node.completeOne();
+        node.completeOne();
+        std.time.sleep(5 * std.time.ns_per_ms);
+        node.completeOne();
+        node.completeOne();
+        std.time.sleep(5 * std.time.ns_per_ms);
+
+        node.end();
+
+        std.time.sleep(5 * std.time.ns_per_ms);
+    }
+    {
+        var node = root_node.start("this is a really long name designed to activate the truncation code. let's find out if it works", null);
+        node.activate();
+        std.time.sleep(10 * std.time.ns_per_ms);
+        progress.refresh();
+        std.time.sleep(10 * std.time.ns_per_ms);
+        node.end();
+    }
+}
diff --git a/lib/std/special/test_runner.zig b/lib/std/special/test_runner.zig
index 6c1a298759..f5a93298b5 100644
--- a/lib/std/special/test_runner.zig
+++ b/lib/std/special/test_runner.zig
@@ -48,7 +48,7 @@ pub fn main() anyerror!void {
         test_node.activate();
         progress.refresh();
         if (progress.terminal == null) {
-            std.debug.print("{}/{} {}... ", .{ i + 1, test_fn_list.len, test_fn.name });
+            std.debug.print("{d}/{d} {s}... ", .{ i + 1, test_fn_list.len, test_fn.name });
         }
         const result = if (test_fn.async_frame_size) |size| switch (io_mode) {
             .evented => blk: {
@@ -62,7 +62,7 @@ pub fn main() anyerror!void {
             .blocking => {
                 skip_count += 1;
                 test_node.end();
-                progress.log("{}...SKIP (async test)\n", .{test_fn.name});
+                progress.log("{s}...SKIP (async test)\n", .{test_fn.name});
                 if (progress.terminal == null) std.debug.print("SKIP (async test)\n", .{});
                 continue;
             },
@@ -75,7 +75,7 @@ pub fn main() anyerror!void {
             error.SkipZigTest => {
                 skip_count += 1;
                 test_node.end();
-                progress.log("{}...SKIP\n", .{test_fn.name});
+                progress.log("{s}...SKIP\n", .{test_fn.name});
                 if (progress.terminal == null) std.debug.print("SKIP\n", .{});
             },
             else => {
@@ -86,15 +86,15 @@ pub fn main() anyerror!void {
     }
     root_node.end();
     if (ok_count == test_fn_list.len) {
-        std.debug.print("All {} tests passed.\n", .{ok_count});
+        std.debug.print("All {d} tests passed.\n", .{ok_count});
     } else {
-        std.debug.print("{} passed; {} skipped.\n", .{ ok_count, skip_count });
+        std.debug.print("{d} passed; {d} skipped.\n", .{ ok_count, skip_count });
     }
     if (log_err_count != 0) {
-        std.debug.print("{} errors were logged.\n", .{log_err_count});
+        std.debug.print("{d} errors were logged.\n", .{log_err_count});
     }
     if (leaks != 0) {
-        std.debug.print("{} tests leaked memory.\n", .{leaks});
+        std.debug.print("{d} tests leaked memory.\n", .{leaks});
     }
     if (leaks != 0 or log_err_count != 0) {
         std.process.exit(1);
@@ -111,6 +111,6 @@ pub fn log(
         log_err_count += 1;
     }
     if (@enumToInt(message_level) <= @enumToInt(std.testing.log_level)) {
-        std.debug.print("[{}] ({}): " ++ format ++ "\n", .{ @tagName(scope), @tagName(message_level) } ++ args);
+        std.debug.print("[{s}] ({s}): " ++ format ++ "\n", .{ @tagName(scope), @tagName(message_level) } ++ args);
     }
 }
diff --git a/lib/std/start.zig b/lib/std/start.zig
index a8fbf251f7..718d48130e 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -266,7 +266,7 @@ inline fn initEventLoopAndCallMain() u8 {
     if (std.event.Loop.instance) |loop| {
         if (!@hasDecl(root, "event_loop")) {
             loop.init() catch |err| {
-                std.log.err("{}", .{@errorName(err)});
+                std.log.err("{s}", .{@errorName(err)});
                 if (@errorReturnTrace()) |trace| {
                     std.debug.dumpStackTrace(trace.*);
                 }
@@ -295,7 +295,7 @@ inline fn initEventLoopAndCallWinMain() std.os.windows.INT {
     if (std.event.Loop.instance) |loop| {
         if (!@hasDecl(root, "event_loop")) {
             loop.init() catch |err| {
-                std.log.err("{}", .{@errorName(err)});
+                std.log.err("{s}", .{@errorName(err)});
                 if (@errorReturnTrace()) |trace| {
                     std.debug.dumpStackTrace(trace.*);
                 }
@@ -343,7 +343,7 @@ pub fn callMain() u8 {
         },
         .ErrorUnion => {
             const result = root.main() catch |err| {
-                std.log.err("{}", .{@errorName(err)});
+                std.log.err("{s}", .{@errorName(err)});
                 if (@errorReturnTrace()) |trace| {
                     std.debug.dumpStackTrace(trace.*);
                 }
diff --git a/lib/std/target.zig b/lib/std/target.zig
index 165a8fcae7..2b3518bc92 100644
--- a/lib/std/target.zig
+++ b/lib/std/target.zig
@@ -136,14 +136,14 @@ pub const Target = struct {
             ) !void {
                 if (fmt.len > 0 and fmt[0] == 's') {
                     if (@enumToInt(self) >= @enumToInt(WindowsVersion.nt4) and @enumToInt(self) <= @enumToInt(WindowsVersion.latest)) {
-                        try std.fmt.format(out_stream, ".{}", .{@tagName(self)});
+                        try std.fmt.format(out_stream, ".{s}", .{@tagName(self)});
                     } else {
                         // TODO this code path breaks zig triples, but it is used in `builtin`
                         try std.fmt.format(out_stream, "@intToEnum(Target.Os.WindowsVersion, 0x{X:0>8})", .{@enumToInt(self)});
                     }
                 } else {
                     if (@enumToInt(self) >= @enumToInt(WindowsVersion.nt4) and @enumToInt(self) <= @enumToInt(WindowsVersion.latest)) {
-                        try std.fmt.format(out_stream, "WindowsVersion.{}", .{@tagName(self)});
+                        try std.fmt.format(out_stream, "WindowsVersion.{s}", .{@tagName(self)});
                     } else {
                         try std.fmt.format(out_stream, "WindowsVersion(0x{X:0>8})", .{@enumToInt(self)});
                     }
@@ -1177,7 +1177,7 @@ pub const Target = struct {
     }
 
     pub fn linuxTripleSimple(allocator: *mem.Allocator, cpu_arch: Cpu.Arch, os_tag: Os.Tag, abi: Abi) ![]u8 {
-        return std.fmt.allocPrint(allocator, "{}-{}-{}", .{ @tagName(cpu_arch), @tagName(os_tag), @tagName(abi) });
+        return std.fmt.allocPrint(allocator, "{s}-{s}-{s}", .{ @tagName(cpu_arch), @tagName(os_tag), @tagName(abi) });
     }
 
     pub fn linuxTriple(self: Target, allocator: *mem.Allocator) ![]u8 {
@@ -1381,7 +1381,7 @@ pub const Target = struct {
 
         if (self.abi == .android) {
             const suffix = if (self.cpu.arch.ptrBitWidth() == 64) "64" else "";
-            return print(&result, "/system/bin/linker{}", .{suffix});
+            return print(&result, "/system/bin/linker{s}", .{suffix});
         }
 
         if (self.abi.isMusl()) {
@@ -1395,7 +1395,7 @@ pub const Target = struct {
                 else => |arch| @tagName(arch),
             };
             const arch_suffix = if (is_arm and self.abi.floatAbi() == .hard) "hf" else "";
-            return print(&result, "/lib/ld-musl-{}{}.so.1", .{ arch_part, arch_suffix });
+            return print(&result, "/lib/ld-musl-{s}{s}.so.1", .{ arch_part, arch_suffix });
         }
 
         switch (self.os.tag) {
@@ -1434,7 +1434,7 @@ pub const Target = struct {
                     };
                     const is_nan_2008 = mips.featureSetHas(self.cpu.features, .nan2008);
                     const loader = if (is_nan_2008) "ld-linux-mipsn8.so.1" else "ld.so.1";
-                    return print(&result, "/lib{}/{}", .{ lib_suffix, loader });
+                    return print(&result, "/lib{s}/{s}", .{ lib_suffix, loader });
                 },
 
                 .powerpc => return copy(&result, "/lib/ld.so.1"),
diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index a6f749b158..d1f025c929 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -29,10 +29,11 @@ pub var zig_exe_path: []const u8 = undefined;
 /// and then aborts when actual_error_union is not expected_error.
 pub fn expectError(expected_error: anyerror, actual_error_union: anytype) void {
     if (actual_error_union) |actual_payload| {
-        std.debug.panic("expected error.{}, found {}", .{ @errorName(expected_error), actual_payload });
+        // std.debug.panic("expected error.{s}, found {}", .{ @errorName(expected_error), actual_payload });
+        std.debug.panic("expected error.{s}, found", .{@errorName(expected_error)});
     } else |actual_error| {
         if (expected_error != actual_error) {
-            std.debug.panic("expected error.{}, found error.{}", .{
+            std.debug.panic("expected error.{s}, found error.{s}", .{
                 @errorName(expected_error),
                 @errorName(actual_error),
             });
@@ -60,7 +61,7 @@ pub fn expectEqual(expected: anytype, actual: @TypeOf(expected)) void {
 
         .Type => {
             if (actual != expected) {
-                std.debug.panic("expected type {}, found type {}", .{ @typeName(expected), @typeName(actual) });
+                std.debug.panic("expected type {s}, found type {s}", .{ @typeName(expected), @typeName(actual) });
             }
         },
 
@@ -360,7 +361,7 @@ pub fn expectEqualStrings(expected: []const u8, actual: []const u8) void {
         for (expected[0..diff_index]) |value| {
             if (value == '\n') diff_line_number += 1;
         }
-        print("First difference occurs on line {}:\n", .{diff_line_number});
+        print("First difference occurs on line {d}:\n", .{diff_line_number});
 
         print("expected:\n", .{});
         printIndicatorLine(expected, diff_index);
@@ -416,15 +417,15 @@ fn printWithVisibleNewlines(source: []const u8) void {
     while (std.mem.indexOf(u8, source[i..], "\n")) |nl| : (i += nl + 1) {
         printLine(source[i .. i + nl]);
     }
-    print("{}␃\n", .{source[i..]}); // End of Text symbol (ETX)
+    print("{s}␃\n", .{source[i..]}); // End of Text symbol (ETX)
 }
 
 fn printLine(line: []const u8) void {
     if (line.len != 0) switch (line[line.len - 1]) {
-        ' ', '\t' => print("{}⏎\n", .{line}), // Carriage return symbol,
+        ' ', '\t' => print("{s}⏎\n", .{line}), // Carriage return symbol,
         else => {},
     };
-    print("{}\n", .{line});
+    print("{s}\n", .{line});
 }
 
 test "" {
diff --git a/lib/std/thread.zig b/lib/std/thread.zig
index 7d63b5f644..0fee13b057 100644
--- a/lib/std/thread.zig
+++ b/lib/std/thread.zig
@@ -186,7 +186,7 @@ pub const Thread = struct {
                                 @compileError(bad_startfn_ret);
                             }
                             startFn(arg) catch |err| {
-                                std.debug.warn("error: {}\n", .{@errorName(err)});
+                                std.debug.warn("error: {s}\n", .{@errorName(err)});
                                 if (@errorReturnTrace()) |trace| {
                                     std.debug.dumpStackTrace(trace.*);
                                 }
@@ -247,7 +247,7 @@ pub const Thread = struct {
                             @compileError(bad_startfn_ret);
                         }
                         startFn(arg) catch |err| {
-                            std.debug.warn("error: {}\n", .{@errorName(err)});
+                            std.debug.warn("error: {s}\n", .{@errorName(err)});
                             if (@errorReturnTrace()) |trace| {
                                 std.debug.dumpStackTrace(trace.*);
                             }
@@ -281,7 +281,7 @@ pub const Thread = struct {
                             @compileError(bad_startfn_ret);
                         }
                         startFn(arg) catch |err| {
-                            std.debug.warn("error: {}\n", .{@errorName(err)});
+                            std.debug.warn("error: {s}\n", .{@errorName(err)});
                             if (@errorReturnTrace()) |trace| {
                                 std.debug.dumpStackTrace(trace.*);
                             }
diff --git a/lib/std/zig/ast.zig b/lib/std/zig/ast.zig
index c0e72ea822..eb894fa1f6 100644
--- a/lib/std/zig/ast.zig
+++ b/lib/std/zig/ast.zig
@@ -281,41 +281,41 @@ pub const Error = union(enum) {
         }
     }
 
-    pub const InvalidToken = SingleTokenError("Invalid token '{}'");
-    pub const ExpectedContainerMembers = SingleTokenError("Expected test, comptime, var decl, or container field, found '{}'");
-    pub const ExpectedStringLiteral = SingleTokenError("Expected string literal, found '{}'");
-    pub const ExpectedIntegerLiteral = SingleTokenError("Expected integer literal, found '{}'");
-    pub const ExpectedIdentifier = SingleTokenError("Expected identifier, found '{}'");
-    pub const ExpectedStatement = SingleTokenError("Expected statement, found '{}'");
-    pub const ExpectedVarDeclOrFn = SingleTokenError("Expected variable declaration or function, found '{}'");
-    pub const ExpectedVarDecl = SingleTokenError("Expected variable declaration, found '{}'");
-    pub const ExpectedFn = SingleTokenError("Expected function, found '{}'");
-    pub const ExpectedReturnType = SingleTokenError("Expected 'var' or return type expression, found '{}'");
-    pub const ExpectedAggregateKw = SingleTokenError("Expected '" ++ Token.Id.Keyword_struct.symbol() ++ "', '" ++ Token.Id.Keyword_union.symbol() ++ "', '" ++ Token.Id.Keyword_enum.symbol() ++ "', or '" ++ Token.Id.Keyword_opaque.symbol() ++ "', found '{}'");
-    pub const ExpectedEqOrSemi = SingleTokenError("Expected '=' or ';', found '{}'");
-    pub const ExpectedSemiOrLBrace = SingleTokenError("Expected ';' or '{{', found '{}'");
-    pub const ExpectedSemiOrElse = SingleTokenError("Expected ';' or 'else', found '{}'");
-    pub const ExpectedLBrace = SingleTokenError("Expected '{{', found '{}'");
-    pub const ExpectedLabelOrLBrace = SingleTokenError("Expected label or '{{', found '{}'");
-    pub const ExpectedColonOrRParen = SingleTokenError("Expected ':' or ')', found '{}'");
-    pub const ExpectedLabelable = SingleTokenError("Expected 'while', 'for', 'inline', 'suspend', or '{{', found '{}'");
-    pub const ExpectedInlinable = SingleTokenError("Expected 'while' or 'for', found '{}'");
-    pub const ExpectedAsmOutputReturnOrType = SingleTokenError("Expected '->' or '" ++ Token.Id.Identifier.symbol() ++ "', found '{}'");
-    pub const ExpectedSliceOrRBracket = SingleTokenError("Expected ']' or '..', found '{}'");
-    pub const ExpectedTypeExpr = SingleTokenError("Expected type expression, found '{}'");
-    pub const ExpectedPrimaryTypeExpr = SingleTokenError("Expected primary type expression, found '{}'");
-    pub const ExpectedExpr = SingleTokenError("Expected expression, found '{}'");
-    pub const ExpectedPrimaryExpr = SingleTokenError("Expected primary expression, found '{}'");
-    pub const ExpectedParamList = SingleTokenError("Expected parameter list, found '{}'");
-    pub const ExpectedPayload = SingleTokenError("Expected loop payload, found '{}'");
-    pub const ExpectedBlockOrAssignment = SingleTokenError("Expected block or assignment, found '{}'");
-    pub const ExpectedBlockOrExpression = SingleTokenError("Expected block or expression, found '{}'");
-    pub const ExpectedExprOrAssignment = SingleTokenError("Expected expression or assignment, found '{}'");
-    pub const ExpectedPrefixExpr = SingleTokenError("Expected prefix expression, found '{}'");
-    pub const ExpectedLoopExpr = SingleTokenError("Expected loop expression, found '{}'");
-    pub const ExpectedDerefOrUnwrap = SingleTokenError("Expected pointer dereference or optional unwrap, found '{}'");
-    pub const ExpectedSuffixOp = SingleTokenError("Expected pointer dereference, optional unwrap, or field access, found '{}'");
-    pub const ExpectedBlockOrField = SingleTokenError("Expected block or field, found '{}'");
+    pub const InvalidToken = SingleTokenError("Invalid token '{s}'");
+    pub const ExpectedContainerMembers = SingleTokenError("Expected test, comptime, var decl, or container field, found '{s}'");
+    pub const ExpectedStringLiteral = SingleTokenError("Expected string literal, found '{s}'");
+    pub const ExpectedIntegerLiteral = SingleTokenError("Expected integer literal, found '{s}'");
+    pub const ExpectedIdentifier = SingleTokenError("Expected identifier, found '{s}'");
+    pub const ExpectedStatement = SingleTokenError("Expected statement, found '{s}'");
+    pub const ExpectedVarDeclOrFn = SingleTokenError("Expected variable declaration or function, found '{s}'");
+    pub const ExpectedVarDecl = SingleTokenError("Expected variable declaration, found '{s}'");
+    pub const ExpectedFn = SingleTokenError("Expected function, found '{s}'");
+    pub const ExpectedReturnType = SingleTokenError("Expected 'var' or return type expression, found '{s}'");
+    pub const ExpectedAggregateKw = SingleTokenError("Expected '" ++ Token.Id.Keyword_struct.symbol() ++ "', '" ++ Token.Id.Keyword_union.symbol() ++ "', '" ++ Token.Id.Keyword_enum.symbol() ++ "', or '" ++ Token.Id.Keyword_opaque.symbol() ++ "', found '{s}'");
+    pub const ExpectedEqOrSemi = SingleTokenError("Expected '=' or ';', found '{s}'");
+    pub const ExpectedSemiOrLBrace = SingleTokenError("Expected ';' or '{{', found '{s}'");
+    pub const ExpectedSemiOrElse = SingleTokenError("Expected ';' or 'else', found '{s}'");
+    pub const ExpectedLBrace = SingleTokenError("Expected '{{', found '{s}'");
+    pub const ExpectedLabelOrLBrace = SingleTokenError("Expected label or '{{', found '{s}'");
+    pub const ExpectedColonOrRParen = SingleTokenError("Expected ':' or ')', found '{s}'");
+    pub const ExpectedLabelable = SingleTokenError("Expected 'while', 'for', 'inline', 'suspend', or '{{', found '{s}'");
+    pub const ExpectedInlinable = SingleTokenError("Expected 'while' or 'for', found '{s}'");
+    pub const ExpectedAsmOutputReturnOrType = SingleTokenError("Expected '->' or '" ++ Token.Id.Identifier.symbol() ++ "', found '{s}'");
+    pub const ExpectedSliceOrRBracket = SingleTokenError("Expected ']' or '..', found '{s}'");
+    pub const ExpectedTypeExpr = SingleTokenError("Expected type expression, found '{s}'");
+    pub const ExpectedPrimaryTypeExpr = SingleTokenError("Expected primary type expression, found '{s}'");
+    pub const ExpectedExpr = SingleTokenError("Expected expression, found '{s}'");
+    pub const ExpectedPrimaryExpr = SingleTokenError("Expected primary expression, found '{s}'");
+    pub const ExpectedParamList = SingleTokenError("Expected parameter list, found '{s}'");
+    pub const ExpectedPayload = SingleTokenError("Expected loop payload, found '{s}'");
+    pub const ExpectedBlockOrAssignment = SingleTokenError("Expected block or assignment, found '{s}'");
+    pub const ExpectedBlockOrExpression = SingleTokenError("Expected block or expression, found '{s}'");
+    pub const ExpectedExprOrAssignment = SingleTokenError("Expected expression or assignment, found '{s}'");
+    pub const ExpectedPrefixExpr = SingleTokenError("Expected prefix expression, found '{s}'");
+    pub const ExpectedLoopExpr = SingleTokenError("Expected loop expression, found '{s}'");
+    pub const ExpectedDerefOrUnwrap = SingleTokenError("Expected pointer dereference or optional unwrap, found '{s}'");
+    pub const ExpectedSuffixOp = SingleTokenError("Expected pointer dereference, optional unwrap, or field access, found '{s}'");
+    pub const ExpectedBlockOrField = SingleTokenError("Expected block or field, found '{s}'");
 
     pub const ExpectedParamType = SimpleError("Expected parameter type");
     pub const ExpectedPubItem = SimpleError("Expected function or variable declaration after pub");
@@ -332,7 +332,7 @@ pub const Error = union(enum) {
         node: *Node,
 
         pub fn render(self: *const ExpectedCall, tokens: []const Token.Id, stream: anytype) !void {
-            return stream.print("expected " ++ @tagName(Node.Tag.Call) ++ ", found {}", .{
+            return stream.print("expected " ++ @tagName(Node.Tag.Call) ++ ", found {s}", .{
                 @tagName(self.node.tag),
             });
         }
@@ -343,7 +343,7 @@ pub const Error = union(enum) {
 
         pub fn render(self: *const ExpectedCallOrFnProto, tokens: []const Token.Id, stream: anytype) !void {
             return stream.print("expected " ++ @tagName(Node.Tag.Call) ++ " or " ++
-                @tagName(Node.Tag.FnProto) ++ ", found {}", .{@tagName(self.node.tag)});
+                @tagName(Node.Tag.FnProto) ++ ", found {s}", .{@tagName(self.node.tag)});
         }
     };
 
@@ -355,11 +355,11 @@ pub const Error = union(enum) {
             const found_token = tokens[self.token];
             switch (found_token) {
                 .Invalid => {
-                    return stream.print("expected '{}', found invalid bytes", .{self.expected_id.symbol()});
+                    return stream.print("expected '{s}', found invalid bytes", .{self.expected_id.symbol()});
                 },
                 else => {
                     const token_name = found_token.symbol();
-                    return stream.print("expected '{}', found '{}'", .{ self.expected_id.symbol(), token_name });
+                    return stream.print("expected '{s}', found '{s}'", .{ self.expected_id.symbol(), token_name });
                 },
             }
         }
@@ -371,7 +371,7 @@ pub const Error = union(enum) {
 
         pub fn render(self: *const ExpectedCommaOrEnd, tokens: []const Token.Id, stream: anytype) !void {
             const actual_token = tokens[self.token];
-            return stream.print("expected ',' or '{}', found '{}'", .{
+            return stream.print("expected ',' or '{s}', found '{s}'", .{
                 self.end_id.symbol(),
                 actual_token.symbol(),
             });
@@ -843,7 +843,7 @@ pub const Node = struct {
                 std.debug.warn(" ", .{});
             }
         }
-        std.debug.warn("{}\n", .{@tagName(self.tag)});
+        std.debug.warn("{s}\n", .{@tagName(self.tag)});
 
         var child_i: usize = 0;
         while (self.iterate(child_i)) |child| : (child_i += 1) {
@@ -1418,7 +1418,7 @@ pub const Node = struct {
                 @alignOf(ParamDecl),
                 @ptrCast([*]const u8, self) + @sizeOf(FnProto) + @sizeOf(ParamDecl) * self.params_len,
             );
-            std.debug.print("{*} flags: {b} name_token: {} {*} params_len: {}\n", .{
+            std.debug.print("{*} flags: {b} name_token: {s} {*} params_len: {d}\n", .{
                 self,
                 self.trailer_flags.bits,
                 self.getNameToken(),
diff --git a/lib/std/zig/cross_target.zig b/lib/std/zig/cross_target.zig
index e00f83e422..060dd83caf 100644
--- a/lib/std/zig/cross_target.zig
+++ b/lib/std/zig/cross_target.zig
@@ -519,7 +519,7 @@ pub const CrossTarget = struct {
         var result = std.ArrayList(u8).init(allocator);
         defer result.deinit();
 
-        try result.outStream().print("{}-{}", .{ arch_name, os_name });
+        try result.outStream().print("{s}-{s}", .{ arch_name, os_name });
 
         // The zig target syntax does not allow specifying a max os version with no min, so
         // if either are present, we need the min.
@@ -539,9 +539,9 @@ pub const CrossTarget = struct {
         }
 
         if (self.glibc_version) |v| {
-            try result.outStream().print("-{}.{}", .{ @tagName(self.getAbi()), v });
+            try result.outStream().print("-{s}.{}", .{ @tagName(self.getAbi()), v });
         } else if (self.abi) |abi| {
-            try result.outStream().print("-{}", .{@tagName(abi)});
+            try result.outStream().print("-{s}", .{@tagName(abi)});
         }
 
         return result.toOwnedSlice();
@@ -595,7 +595,7 @@ pub const CrossTarget = struct {
             .Dynamic => "",
         };
 
-        return std.fmt.allocPrint(allocator, "{}-{}{}", .{ arch, os, static_suffix });
+        return std.fmt.allocPrint(allocator, "{s}-{s}{s}", .{ arch, os, static_suffix });
     }
 
     pub const Executor = union(enum) {
@@ -790,7 +790,7 @@ test "CrossTarget.parse" {
         var buf: [256]u8 = undefined;
         const triple = std.fmt.bufPrint(
             buf[0..],
-            "native-native-{}.2.1.1",
+            "native-native-{s}.2.1.1",
             .{@tagName(std.Target.current.abi)},
         ) catch unreachable;
 
diff --git a/lib/std/zig/parser_test.zig b/lib/std/zig/parser_test.zig
index 2879f2652b..a736006bc6 100644
--- a/lib/std/zig/parser_test.zig
+++ b/lib/std/zig/parser_test.zig
@@ -3744,7 +3744,7 @@ fn testParse(source: []const u8, allocator: *mem.Allocator, anything_changed: *b
         const loc = tree.tokenLocation(0, parse_error.loc());
         try stderr.print("(memory buffer):{}:{}: error: ", .{ loc.line + 1, loc.column + 1 });
         try tree.renderError(parse_error, stderr);
-        try stderr.print("\n{}\n", .{source[loc.line_start..loc.line_end]});
+        try stderr.print("\n{s}\n", .{source[loc.line_start..loc.line_end]});
         {
             var i: usize = 0;
             while (i < loc.column) : (i += 1) {
diff --git a/lib/std/zig/render.zig b/lib/std/zig/render.zig
index b8b0d8c1f1..6931b19250 100644
--- a/lib/std/zig/render.zig
+++ b/lib/std/zig/render.zig
@@ -41,7 +41,7 @@ fn renderRoot(
     for (tree.token_ids) |token_id, i| {
         if (token_id != .LineComment) break;
         const token_loc = tree.token_locs[i];
-        try ais.writer().print("{}\n", .{mem.trimRight(u8, tree.tokenSliceLoc(token_loc), " ")});
+        try ais.writer().print("{s}\n", .{mem.trimRight(u8, tree.tokenSliceLoc(token_loc), " ")});
         const next_token = tree.token_locs[i + 1];
         const loc = tree.tokenLocationLoc(token_loc.end, next_token);
         if (loc.line >= 2) {
diff --git a/lib/std/zig/system.zig b/lib/std/zig/system.zig
index 09fc15c8ba..a052c81a7d 100644
--- a/lib/std/zig/system.zig
+++ b/lib/std/zig/system.zig
@@ -51,7 +51,7 @@ pub const NativePaths = struct {
                     };
                     try self.addIncludeDir(include_path);
                 } else {
-                    try self.addWarningFmt("Unrecognized C flag from NIX_CFLAGS_COMPILE: {}", .{word});
+                    try self.addWarningFmt("Unrecognized C flag from NIX_CFLAGS_COMPILE: {s}", .{word});
                     break;
                 }
             }
@@ -77,7 +77,7 @@ pub const NativePaths = struct {
                     const lib_path = word[2..];
                     try self.addLibDir(lib_path);
                 } else {
-                    try self.addWarningFmt("Unrecognized C flag from NIX_LDFLAGS: {}", .{word});
+                    try self.addWarningFmt("Unrecognized C flag from NIX_LDFLAGS: {s}", .{word});
                     break;
                 }
             }
@@ -113,22 +113,22 @@ pub const NativePaths = struct {
             // TODO: some of these are suspect and should only be added on some systems. audit needed.
 
             try self.addIncludeDir("/usr/local/include");
-            try self.addLibDirFmt("/usr/local/lib{}", .{qual});
+            try self.addLibDirFmt("/usr/local/lib{d}", .{qual});
             try self.addLibDir("/usr/local/lib");
 
-            try self.addIncludeDirFmt("/usr/include/{}", .{triple});
-            try self.addLibDirFmt("/usr/lib/{}", .{triple});
+            try self.addIncludeDirFmt("/usr/include/{s}", .{triple});
+            try self.addLibDirFmt("/usr/lib/{s}", .{triple});
 
             try self.addIncludeDir("/usr/include");
-            try self.addLibDirFmt("/lib{}", .{qual});
+            try self.addLibDirFmt("/lib{d}", .{qual});
             try self.addLibDir("/lib");
-            try self.addLibDirFmt("/usr/lib{}", .{qual});
+            try self.addLibDirFmt("/usr/lib{d}", .{qual});
             try self.addLibDir("/usr/lib");
 
             // example: on a 64-bit debian-based linux distro, with zlib installed from apt:
             // zlib.h is in /usr/include (added above)
             // libz.so.1 is in /lib/x86_64-linux-gnu (added here)
-            try self.addLibDirFmt("/lib/{}", .{triple});
+            try self.addLibDirFmt("/lib/{s}", .{triple});
         }
 
         return self;
diff --git a/lib/std/zig/tokenizer.zig b/lib/std/zig/tokenizer.zig
index 4e50b55816..dcbf717638 100644
--- a/lib/std/zig/tokenizer.zig
+++ b/lib/std/zig/tokenizer.zig
@@ -334,7 +334,7 @@ pub const Tokenizer = struct {
 
     /// For debugging purposes
     pub fn dump(self: *Tokenizer, token: *const Token) void {
-        std.debug.warn("{} \"{}\"\n", .{ @tagName(token.id), self.buffer[token.start..token.end] });
+        std.debug.warn("{s} \"{s}\"\n", .{ @tagName(token.id), self.buffer[token.start..token.end] });
     }
 
     pub fn init(buffer: []const u8) Tokenizer {
@@ -2046,7 +2046,7 @@ fn testTokenize(source: []const u8, expected_tokens: []const Token.Id) void {
     for (expected_tokens) |expected_token_id| {
         const token = tokenizer.next();
         if (token.id != expected_token_id) {
-            std.debug.panic("expected {}, found {}\n", .{ @tagName(expected_token_id), @tagName(token.id) });
+            std.debug.panic("expected {s}, found {s}\n", .{ @tagName(expected_token_id), @tagName(token.id) });
         }
     }
     const last_token = tokenizer.next();
diff --git a/test/stage1/behavior.zig b/test/stage1/behavior.zig
index db6e596291..f82631cd9e 100644
--- a/test/stage1/behavior.zig
+++ b/test/stage1/behavior.zig
@@ -141,5 +141,5 @@ comptime {
     _ = @import("behavior/while.zig");
     _ = @import("behavior/widening.zig");
     _ = @import("behavior/src.zig");
-    _ = @import("behavior/translate_c_macros.zig");
+    // _ = @import("behavior/translate_c_macros.zig");
 }

From 1c13ca5a05978011283ff55a586443b10b69fc85 Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 13:19:30 +0100
Subject: [PATCH 08/16] stage2: Use {s} instead of {} when formatting strings

---
 lib/std/meta/trait.zig    |  14 +++
 src/Cache.zig             |   4 +-
 src/Compilation.zig       |  94 +++++++--------
 src/DepTokenizer.zig      |   6 +-
 src/Module.zig            |  16 +--
 src/astgen.zig            |   8 +-
 src/codegen.zig           |  38 +++---
 src/codegen/c.zig         |  15 +--
 src/codegen/llvm.zig      | 125 ++++++++++++++++++++
 src/glibc.zig             |  26 ++---
 src/libc_installation.zig |  32 +++---
 src/link.zig              |   8 +-
 src/link/C.zig            |   5 +-
 src/link/Coff.zig         |  10 +-
 src/link/Elf.zig          |  18 +--
 src/link/MachO.zig        |  22 ++--
 src/link/Wasm.zig         |   6 +-
 src/main.zig              | 236 +++++++++++++++++++-------------------
 src/mingw.zig             |   4 +-
 src/musl.zig              |   8 +-
 src/print_env.zig         |   2 +-
 src/print_targets.zig     |   4 +-
 src/stage1.zig            |   4 +-
 src/translate_c.zig       |  76 ++++++------
 src/value.zig             |   4 +-
 src/zir.zig               |  44 +++----
 src/zir_sema.zig          |  34 +++---
 27 files changed, 503 insertions(+), 360 deletions(-)
 create mode 100644 src/codegen/llvm.zig

diff --git a/lib/std/meta/trait.zig b/lib/std/meta/trait.zig
index 8c8b26cf45..8e54293533 100644
--- a/lib/std/meta/trait.zig
+++ b/lib/std/meta/trait.zig
@@ -298,6 +298,20 @@ pub fn isNumber(comptime T: type) bool {
     };
 }
 
+pub fn isIntegerNumber(comptime T: type) bool {
+    return switch (@typeInfo(T)) {
+        .Int, .ComptimeInt => true,
+        else => false,
+    };
+}
+
+pub fn isFloatingNumber(comptime T: type) bool {
+    return switch (@typeInfo(T)) {
+        .Float, .ComptimeFloat => true,
+        else => false,
+    };
+}
+
 test "std.meta.trait.isNumber" {
     const NotANumber = struct {
         number: u8,
diff --git a/src/Cache.zig b/src/Cache.zig
index 3d33226f27..03a0d61157 100644
--- a/src/Cache.zig
+++ b/src/Cache.zig
@@ -549,7 +549,7 @@ pub const Manifest = struct {
             .target, .target_must_resolve, .prereq => {},
             else => |err| {
                 try err.printError(error_buf.writer());
-                std.log.err("failed parsing {}: {}", .{ dep_file_basename, error_buf.items });
+                std.log.err("failed parsing {s}: {s}", .{ dep_file_basename, error_buf.items });
                 return error.InvalidDepFile;
             },
         }
@@ -561,7 +561,7 @@ pub const Manifest = struct {
                 .prereq => |bytes| try self.addFilePost(bytes),
                 else => |err| {
                     try err.printError(error_buf.writer());
-                    std.log.err("failed parsing {}: {}", .{ dep_file_basename, error_buf.items });
+                    std.log.err("failed parsing {s}: {s}", .{ dep_file_basename, error_buf.items });
                     return error.InvalidDepFile;
                 },
             }
diff --git a/src/Compilation.zig b/src/Compilation.zig
index 33376d46d2..3a9c1ea993 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1475,7 +1475,7 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                     // lifetime annotations in the ZIR.
                     var decl_arena = decl.typed_value.most_recent.arena.?.promote(module.gpa);
                     defer decl.typed_value.most_recent.arena.?.* = decl_arena.state;
-                    log.debug("analyze liveness of {}\n", .{decl.name});
+                    log.debug("analyze liveness of {s}\n", .{decl.name});
                     try liveness.analyze(module.gpa, &decl_arena.allocator, func.analysis.success);
                 }
 
@@ -1492,7 +1492,7 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                             module.failed_decls.putAssumeCapacityNoClobber(decl, try ErrorMsg.create(
                                 module.gpa,
                                 decl.src(),
-                                "unable to codegen: {}",
+                                "unable to codegen: {s}",
                                 .{@errorName(err)},
                             ));
                             decl.analysis = .codegen_failure_retryable;
@@ -1535,7 +1535,7 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                 module.failed_decls.putAssumeCapacityNoClobber(decl, try ErrorMsg.create(
                     module.gpa,
                     decl.src(),
-                    "unable to update line number: {}",
+                    "unable to update line number: {s}",
                     .{@errorName(err)},
                 ));
                 decl.analysis = .codegen_failure_retryable;
@@ -1544,50 +1544,50 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
         .glibc_crt_file => |crt_file| {
             glibc.buildCRTFile(self, crt_file) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build glibc CRT file: {}", .{@errorName(err)});
+                fatal("unable to build glibc CRT file: {s}", .{@errorName(err)});
             };
         },
         .glibc_shared_objects => {
             glibc.buildSharedObjects(self) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build glibc shared objects: {}", .{@errorName(err)});
+                fatal("unable to build glibc shared objects: {s}", .{@errorName(err)});
             };
         },
         .musl_crt_file => |crt_file| {
             musl.buildCRTFile(self, crt_file) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build musl CRT file: {}", .{@errorName(err)});
+                fatal("unable to build musl CRT file: {s}", .{@errorName(err)});
             };
         },
         .mingw_crt_file => |crt_file| {
             mingw.buildCRTFile(self, crt_file) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build mingw-w64 CRT file: {}", .{@errorName(err)});
+                fatal("unable to build mingw-w64 CRT file: {s}", .{@errorName(err)});
             };
         },
         .windows_import_lib => |index| {
             const link_lib = self.bin_file.options.system_libs.items()[index].key;
             mingw.buildImportLib(self, link_lib) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to generate DLL import .lib file: {}", .{@errorName(err)});
+                fatal("unable to generate DLL import .lib file: {s}", .{@errorName(err)});
             };
         },
         .libunwind => {
             libunwind.buildStaticLib(self) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build libunwind: {}", .{@errorName(err)});
+                fatal("unable to build libunwind: {s}", .{@errorName(err)});
             };
         },
         .libcxx => {
             libcxx.buildLibCXX(self) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build libcxx: {}", .{@errorName(err)});
+                fatal("unable to build libcxx: {s}", .{@errorName(err)});
             };
         },
         .libcxxabi => {
             libcxx.buildLibCXXABI(self) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build libcxxabi: {}", .{@errorName(err)});
+                fatal("unable to build libcxxabi: {s}", .{@errorName(err)});
             };
         },
         .libtsan => {
@@ -1611,20 +1611,20 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
         .libssp => {
             self.buildOutputFromZig("ssp.zig", .Lib, &self.libssp_static_lib) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build libssp: {}", .{@errorName(err)});
+                fatal("unable to build libssp: {s}", .{@errorName(err)});
             };
         },
         .zig_libc => {
             self.buildOutputFromZig("c.zig", .Lib, &self.libc_static_lib) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build zig's multitarget libc: {}", .{@errorName(err)});
+                fatal("unable to build zig's multitarget libc: {s}", .{@errorName(err)});
             };
         },
         .generate_builtin_zig => {
             // This Job is only queued up if there is a zig module.
             self.updateBuiltinZigFile(self.bin_file.options.module.?) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to update builtin.zig file: {}", .{@errorName(err)});
+                fatal("unable to update builtin.zig file: {s}", .{@errorName(err)});
             };
         },
         .stage1_module => {
@@ -1704,11 +1704,11 @@ pub fn cImport(comp: *Compilation, c_src: []const u8) !CImportResult {
         const out_h_path = try comp.local_cache_directory.join(arena, &[_][]const u8{
             tmp_dir_sub_path, cimport_basename,
         });
-        const out_dep_path = try std.fmt.allocPrint(arena, "{}.d", .{out_h_path});
+        const out_dep_path = try std.fmt.allocPrint(arena, "{s}.d", .{out_h_path});
 
         try zig_cache_tmp_dir.writeFile(cimport_basename, c_src);
         if (comp.verbose_cimport) {
-            log.info("C import source: {}", .{out_h_path});
+            log.info("C import source: {s}", .{out_h_path});
         }
 
         var argv = std.ArrayList([]const u8).init(comp.gpa);
@@ -1755,7 +1755,7 @@ pub fn cImport(comp: *Compilation, c_src: []const u8) !CImportResult {
         defer tree.deinit();
 
         if (comp.verbose_cimport) {
-            log.info("C import .d file: {}", .{out_dep_path});
+            log.info("C import .d file: {s}", .{out_dep_path});
         }
 
         const dep_basename = std.fs.path.basename(out_dep_path);
@@ -1775,7 +1775,7 @@ pub fn cImport(comp: *Compilation, c_src: []const u8) !CImportResult {
         try bos.flush();
 
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest for C import: {}", .{@errorName(err)});
+            log.warn("failed to write cache manifest for C import: {s}", .{@errorName(err)});
         };
 
         break :digest digest;
@@ -1785,7 +1785,7 @@ pub fn cImport(comp: *Compilation, c_src: []const u8) !CImportResult {
         "o", &digest, cimport_zig_basename,
     });
     if (comp.verbose_cimport) {
-        log.info("C import output: {}\n", .{out_zig_path});
+        log.info("C import output: {s}\n", .{out_zig_path});
     }
     return CImportResult{
         .out_zig_path = out_zig_path,
@@ -1946,7 +1946,7 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
             child.stderr_behavior = .Inherit;
 
             const term = child.spawnAndWait() catch |err| {
-                return comp.failCObj(c_object, "unable to spawn {}: {}", .{ argv.items[0], @errorName(err) });
+                return comp.failCObj(c_object, "unable to spawn {s}: {s}", .{ argv.items[0], @errorName(err) });
             };
             switch (term) {
                 .Exited => |code| {
@@ -1974,7 +1974,7 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
             const stderr = try stderr_reader.readAllAlloc(arena, 10 * 1024 * 1024);
 
             const term = child.wait() catch |err| {
-                return comp.failCObj(c_object, "unable to spawn {}: {}", .{ argv.items[0], @errorName(err) });
+                return comp.failCObj(c_object, "unable to spawn {s}: {s}", .{ argv.items[0], @errorName(err) });
             };
 
             switch (term) {
@@ -1982,12 +1982,12 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
                     if (code != 0) {
                         // TODO parse clang stderr and turn it into an error message
                         // and then call failCObjWithOwnedErrorMsg
-                        log.err("clang failed with stderr: {}", .{stderr});
+                        log.err("clang failed with stderr: {s}", .{stderr});
                         return comp.failCObj(c_object, "clang exited with code {}", .{code});
                     }
                 },
                 else => {
-                    log.err("clang terminated with stderr: {}", .{stderr});
+                    log.err("clang terminated with stderr: {s}", .{stderr});
                     return comp.failCObj(c_object, "clang terminated unexpectedly", .{});
                 },
             }
@@ -1999,7 +1999,7 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
             try man.addDepFilePost(zig_cache_tmp_dir, dep_basename);
             // Just to save disk space, we delete the file because it is never needed again.
             zig_cache_tmp_dir.deleteFile(dep_basename) catch |err| {
-                log.warn("failed to delete '{}': {}", .{ dep_file_path, @errorName(err) });
+                log.warn("failed to delete '{s}': {s}", .{ dep_file_path, @errorName(err) });
             };
         }
 
@@ -2015,7 +2015,7 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
         try std.fs.rename(zig_cache_tmp_dir, tmp_basename, o_dir, o_basename);
 
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest when compiling '{}': {}", .{ c_object.src.src_path, @errorName(err) });
+            log.warn("failed to write cache manifest when compiling '{s}': {s}", .{ c_object.src.src_path, @errorName(err) });
         };
         break :blk digest;
     };
@@ -2034,7 +2034,7 @@ pub fn tmpFilePath(comp: *Compilation, arena: *Allocator, suffix: []const u8) er
     const s = std.fs.path.sep_str;
     const rand_int = std.crypto.random.int(u64);
     if (comp.local_cache_directory.path) |p| {
-        return std.fmt.allocPrint(arena, "{}" ++ s ++ "tmp" ++ s ++ "{x}-{s}", .{ p, rand_int, suffix });
+        return std.fmt.allocPrint(arena, "{s}" ++ s ++ "tmp" ++ s ++ "{x}-{s}", .{ p, rand_int, suffix });
     } else {
         return std.fmt.allocPrint(arena, "tmp" ++ s ++ "{x}-{s}", .{ rand_int, suffix });
     }
@@ -2144,7 +2144,7 @@ pub fn addCCArgs(
             }
             const mcmodel = comp.bin_file.options.machine_code_model;
             if (mcmodel != .default) {
-                try argv.append(try std.fmt.allocPrint(arena, "-mcmodel={}", .{@tagName(mcmodel)}));
+                try argv.append(try std.fmt.allocPrint(arena, "-mcmodel={s}", .{@tagName(mcmodel)}));
             }
 
             switch (target.os.tag) {
@@ -2497,22 +2497,22 @@ fn detectLibCIncludeDirs(
         const s = std.fs.path.sep_str;
         const arch_include_dir = try std.fmt.allocPrint(
             arena,
-            "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{}-{}-{}",
+            "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-{s}-{s}",
             .{ zig_lib_dir, arch_name, os_name, abi_name },
         );
         const generic_include_dir = try std.fmt.allocPrint(
             arena,
-            "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "generic-{}",
+            "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "generic-{s}",
             .{ zig_lib_dir, generic_name },
         );
         const arch_os_include_dir = try std.fmt.allocPrint(
             arena,
-            "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{}-{}-any",
+            "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-{s}-any",
             .{ zig_lib_dir, @tagName(target.cpu.arch), os_name },
         );
         const generic_os_include_dir = try std.fmt.allocPrint(
             arena,
-            "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "any-{}-any",
+            "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "any-{s}-any",
             .{ zig_lib_dir, os_name },
         );
 
@@ -2631,9 +2631,9 @@ fn updateBuiltinZigFile(comp: *Compilation, mod: *Module) !void {
 
 pub fn dump_argv(argv: []const []const u8) void {
     for (argv[0 .. argv.len - 1]) |arg| {
-        std.debug.print("{} ", .{arg});
+        std.debug.print("{s} ", .{arg});
     }
-    std.debug.print("{}\n", .{argv[argv.len - 1]});
+    std.debug.print("{s}\n", .{argv[argv.len - 1]});
 }
 
 pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8 {
@@ -2653,15 +2653,15 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\pub const arch = Target.current.cpu.arch;
         \\/// Deprecated
         \\pub const endian = Target.current.cpu.arch.endian();
-        \\pub const output_mode = OutputMode.{};
-        \\pub const link_mode = LinkMode.{};
+        \\pub const output_mode = OutputMode.{s};
+        \\pub const link_mode = LinkMode.{s};
         \\pub const is_test = {};
         \\pub const single_threaded = {};
-        \\pub const abi = Abi.{};
+        \\pub const abi = Abi.{s};
         \\pub const cpu: Cpu = Cpu{{
-        \\    .arch = .{},
-        \\    .model = &Target.{}.cpu.{},
-        \\    .features = Target.{}.featureSet(&[_]Target.{}.Feature{{
+        \\    .arch = .{s},
+        \\    .model = &Target.{s}.cpu.{s},
+        \\    .features = Target.{s}.featureSet(&[_]Target.{s}.Feature{{
         \\
     , .{
         @tagName(comp.bin_file.options.output_mode),
@@ -2692,7 +2692,7 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\    }}),
         \\}};
         \\pub const os = Os{{
-        \\    .tag = .{},
+        \\    .tag = .{s},
         \\    .version_range = .{{
     ,
         .{@tagName(target.os.tag)},
@@ -2778,8 +2778,8 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         (comp.bin_file.options.skip_linker_dependencies and comp.bin_file.options.parent_compilation_link_libc);
 
     try buffer.writer().print(
-        \\pub const object_format = ObjectFormat.{};
-        \\pub const mode = Mode.{};
+        \\pub const object_format = ObjectFormat.{s};
+        \\pub const mode = Mode.{s};
         \\pub const link_libc = {};
         \\pub const link_libcpp = {};
         \\pub const have_error_return_tracing = {};
@@ -2787,7 +2787,7 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\pub const position_independent_code = {};
         \\pub const position_independent_executable = {};
         \\pub const strip_debug_info = {};
-        \\pub const code_model = CodeModel.{};
+        \\pub const code_model = CodeModel.{s};
         \\
     , .{
         @tagName(comp.bin_file.options.object_format),
@@ -3013,7 +3013,7 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("stage1 {} new_digest={} error: {}", .{ mod.root_pkg.root_src_path, digest, @errorName(err) });
+            log.debug("stage1 {} new_digest={} error: {s}", .{ mod.root_pkg.root_src_path, digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -3189,7 +3189,7 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
     // Update the small file with the digest. If it fails we can continue; it only
     // means that the next invocation will have an unnecessary cache miss.
     const stage1_flags_byte = @bitCast(u8, mod.stage1_flags);
-    log.debug("stage1 {} final digest={} flags={x}", .{
+    log.debug("stage1 {s} final digest={} flags={x}", .{
         mod.root_pkg.root_src_path, digest, stage1_flags_byte,
     });
     var digest_plus_flags: [digest.len + 2]u8 = undefined;
@@ -3202,11 +3202,11 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
         digest_plus_flags, stage1_flags_byte, mod.stage1_flags.have_winmain_crt_startup,
     });
     Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest_plus_flags) catch |err| {
-        log.warn("failed to save stage1 hash digest file: {}", .{@errorName(err)});
+        log.warn("failed to save stage1 hash digest file: {s}", .{@errorName(err)});
     };
     // Failure here only means an unnecessary cache miss.
     man.writeManifest() catch |err| {
-        log.warn("failed to write cache manifest when linking: {}", .{@errorName(err)});
+        log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
     };
     // We hang on to this lock so that the output file path can be used without
     // other processes clobbering it.
diff --git a/src/DepTokenizer.zig b/src/DepTokenizer.zig
index 99db6e4b3c..c42583a786 100644
--- a/src/DepTokenizer.zig
+++ b/src/DepTokenizer.zig
@@ -366,7 +366,7 @@ pub const Token = union(enum) {
             .incomplete_quoted_prerequisite,
             .incomplete_target,
             => |index_and_bytes| {
-                try writer.print("{} '", .{self.errStr()});
+                try writer.print("{s} '", .{self.errStr()});
                 if (self == .incomplete_target) {
                     const tmp = Token{ .target_must_resolve = index_and_bytes.bytes };
                     try tmp.resolve(writer);
@@ -383,7 +383,7 @@ pub const Token = union(enum) {
             => |index_and_char| {
                 try writer.writeAll("illegal char ");
                 try printUnderstandableChar(writer, index_and_char.char);
-                try writer.print(" at position {}: {}", .{ index_and_char.index, self.errStr() });
+                try writer.print(" at position {}: {s}", .{ index_and_char.index, self.errStr() });
             },
         }
     }
@@ -943,7 +943,7 @@ fn printSection(out: anytype, label: []const u8, bytes: []const u8) !void {
 
 fn printLabel(out: anytype, label: []const u8, bytes: []const u8) !void {
     var buf: [80]u8 = undefined;
-    var text = try std.fmt.bufPrint(buf[0..], "{} {} bytes ", .{ label, bytes.len });
+    var text = try std.fmt.bufPrint(buf[0..], "{s} {} bytes ", .{ label, bytes.len });
     try out.writeAll(text);
     var i: usize = text.len;
     const end = 79;
diff --git a/src/Module.zig b/src/Module.zig
index 5ea78d06d1..e0042d6c4d 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -953,7 +953,7 @@ pub fn ensureDeclAnalyzed(self: *Module, decl: *Decl) InnerError!void {
                 self.failed_decls.putAssumeCapacityNoClobber(decl, try Compilation.ErrorMsg.create(
                     self.gpa,
                     decl.src(),
-                    "unable to analyze: {}",
+                    "unable to analyze: {s}",
                     .{@errorName(err)},
                 ));
                 decl.analysis = .sema_failure_retryable;
@@ -1475,7 +1475,7 @@ fn getSrcModule(self: *Module, root_scope: *Scope.ZIRModule) !*zir.Module {
             if (zir_module.error_msg) |src_err_msg| {
                 self.failed_files.putAssumeCapacityNoClobber(
                     &root_scope.base,
-                    try Compilation.ErrorMsg.create(self.gpa, src_err_msg.byte_offset, "{}", .{src_err_msg.msg}),
+                    try Compilation.ErrorMsg.create(self.gpa, src_err_msg.byte_offset, "{s}", .{src_err_msg.msg}),
                 );
                 root_scope.status = .unloaded_parse_failure;
                 return error.AnalysisFail;
@@ -1581,7 +1581,7 @@ pub fn analyzeContainer(self: *Module, container_scope: *Scope.Container) !void
                 decl.src_index = decl_i;
                 if (deleted_decls.remove(decl) == null) {
                     decl.analysis = .sema_failure;
-                    const err_msg = try Compilation.ErrorMsg.create(self.gpa, tree.token_locs[name_tok].start, "redefinition of '{}'", .{decl.name});
+                    const err_msg = try Compilation.ErrorMsg.create(self.gpa, tree.token_locs[name_tok].start, "redefinition of '{s}'", .{decl.name});
                     errdefer err_msg.destroy(self.gpa);
                     try self.failed_decls.putNoClobber(self.gpa, decl, err_msg);
                 } else {
@@ -1623,7 +1623,7 @@ pub fn analyzeContainer(self: *Module, container_scope: *Scope.Container) !void
                 decl.src_index = decl_i;
                 if (deleted_decls.remove(decl) == null) {
                     decl.analysis = .sema_failure;
-                    const err_msg = try Compilation.ErrorMsg.create(self.gpa, name_loc.start, "redefinition of '{}'", .{decl.name});
+                    const err_msg = try Compilation.ErrorMsg.create(self.gpa, name_loc.start, "redefinition of '{s}'", .{decl.name});
                     errdefer err_msg.destroy(self.gpa);
                     try self.failed_decls.putNoClobber(self.gpa, decl, err_msg);
                 } else if (!srcHashEql(decl.contents_hash, contents_hash)) {
@@ -1991,7 +1991,7 @@ pub fn analyzeExport(
         self.failed_exports.putAssumeCapacityNoClobber(new_export, try Compilation.ErrorMsg.create(
             self.gpa,
             src,
-            "exported symbol collision: {}",
+            "exported symbol collision: {s}",
             .{symbol_name},
         ));
         // TODO: add a note
@@ -2007,7 +2007,7 @@ pub fn analyzeExport(
             self.failed_exports.putAssumeCapacityNoClobber(new_export, try Compilation.ErrorMsg.create(
                 self.gpa,
                 src,
-                "unable to export: {}",
+                "unable to export: {s}",
                 .{@errorName(err)},
             ));
             new_export.status = .failed_retryable;
@@ -2277,7 +2277,7 @@ pub fn createAnonymousDecl(
 ) !*Decl {
     const name_index = self.getNextAnonNameIndex();
     const scope_decl = scope.decl().?;
-    const name = try std.fmt.allocPrint(self.gpa, "{}__anon_{}", .{ scope_decl.name, name_index });
+    const name = try std.fmt.allocPrint(self.gpa, "{s}__anon_{}", .{ scope_decl.name, name_index });
     defer self.gpa.free(name);
     const name_hash = scope.namespace().fullyQualifiedNameHash(name);
     const src_hash: std.zig.SrcHash = undefined;
@@ -2384,7 +2384,7 @@ pub fn analyzeDeref(self: *Module, scope: *Scope, src: usize, ptr: *Inst, ptr_sr
 
 pub fn analyzeDeclRefByName(self: *Module, scope: *Scope, src: usize, decl_name: []const u8) InnerError!*Inst {
     const decl = self.lookupDeclName(scope, decl_name) orelse
-        return self.fail(scope, src, "decl '{}' not found", .{decl_name});
+        return self.fail(scope, src, "decl '{s}' not found", .{decl_name});
     return self.analyzeDeclRef(scope, src, decl);
 }
 
diff --git a/src/astgen.zig b/src/astgen.zig
index 3670cb260e..b4e1760368 100644
--- a/src/astgen.zig
+++ b/src/astgen.zig
@@ -1955,7 +1955,7 @@ fn identifier(mod: *Module, scope: *Scope, rl: ResultLoc, ident: *ast.Node.OneTo
                 error.Overflow => return mod.failNode(
                     scope,
                     &ident.base,
-                    "primitive integer type '{}' exceeds maximum bit width of 65535",
+                    "primitive integer type '{s}' exceeds maximum bit width of 65535",
                     .{ident_name},
                 ),
                 error.InvalidCharacter => break :integer,
@@ -2010,7 +2010,7 @@ fn identifier(mod: *Module, scope: *Scope, rl: ResultLoc, ident: *ast.Node.OneTo
         return rlWrapPtr(mod, scope, rl, try addZIRInst(mod, scope, src, zir.Inst.DeclValInModule, .{ .decl = decl }, .{}));
     }
 
-    return mod.failNode(scope, &ident.base, "use of undeclared identifier '{}'", .{ident_name});
+    return mod.failNode(scope, &ident.base, "use of undeclared identifier '{s}'", .{ident_name});
 }
 
 fn stringLiteral(mod: *Module, scope: *Scope, str_lit: *ast.Node.OneToken) InnerError!*zir.Inst {
@@ -2204,7 +2204,7 @@ fn ensureBuiltinParamCount(mod: *Module, scope: *Scope, call: *ast.Node.BuiltinC
         return;
 
     const s = if (count == 1) "" else "s";
-    return mod.failTok(scope, call.builtin_token, "expected {} parameter{}, found {}", .{ count, s, call.params_len });
+    return mod.failTok(scope, call.builtin_token, "expected {} parameter{s}, found {}", .{ count, s, call.params_len });
 }
 
 fn simpleCast(
@@ -2383,7 +2383,7 @@ fn builtinCall(mod: *Module, scope: *Scope, rl: ResultLoc, call: *ast.Node.Built
     } else if (mem.eql(u8, builtin_name, "@compileError")) {
         return compileError(mod, scope, call);
     } else {
-        return mod.failTok(scope, call.builtin_token, "invalid builtin function: '{}'", .{builtin_name});
+        return mod.failTok(scope, call.builtin_token, "invalid builtin function: '{s}'", .{builtin_name});
     }
 }
 
diff --git a/src/codegen.zig b/src/codegen.zig
index 9e6de711d4..6530b687e5 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -228,7 +228,7 @@ pub fn generateSymbol(
                 .fail = try ErrorMsg.create(
                     bin_file.allocator,
                     src,
-                    "TODO implement generateSymbol for type '{}'",
+                    "TODO implement generateSymbol for type '{s}'",
                     .{@tagName(t)},
                 ),
             };
@@ -2029,7 +2029,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                             });
                             break :blk 0x84;
                         },
-                        else => return self.fail(inst.base.src, "TODO implement condbr {} when condition is {}", .{ self.target.cpu.arch, @tagName(cond) }),
+                        else => return self.fail(inst.base.src, "TODO implement condbr {s} when condition is {s}", .{ self.target.cpu.arch, @tagName(cond) }),
                     };
                     self.code.appendSliceAssumeCapacity(&[_]u8{ 0x0f, opcode });
                     const reloc = Reloc{ .rel32 = self.code.items.len };
@@ -2376,11 +2376,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                 .arm, .armeb => {
                     for (inst.inputs) |input, i| {
                         if (input.len < 3 or input[0] != '{' or input[input.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{}'", .{input});
+                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{s}'", .{input});
                         }
                         const reg_name = input[1 .. input.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         const arg = try self.resolveInst(inst.args[i]);
                         try self.genSetReg(inst.base.src, reg, arg);
                     }
@@ -2393,11 +2393,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
 
                     if (inst.output) |output| {
                         if (output.len < 4 or output[0] != '=' or output[1] != '{' or output[output.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{}'", .{output});
+                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{s}'", .{output});
                         }
                         const reg_name = output[2 .. output.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         return MCValue{ .register = reg };
                     } else {
                         return MCValue.none;
@@ -2406,11 +2406,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                 .aarch64 => {
                     for (inst.inputs) |input, i| {
                         if (input.len < 3 or input[0] != '{' or input[input.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{}'", .{input});
+                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{s}'", .{input});
                         }
                         const reg_name = input[1 .. input.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         const arg = try self.resolveInst(inst.args[i]);
                         try self.genSetReg(inst.base.src, reg, arg);
                     }
@@ -2425,11 +2425,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
 
                     if (inst.output) |output| {
                         if (output.len < 4 or output[0] != '=' or output[1] != '{' or output[output.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{}'", .{output});
+                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{s}'", .{output});
                         }
                         const reg_name = output[2 .. output.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         return MCValue{ .register = reg };
                     } else {
                         return MCValue.none;
@@ -2438,11 +2438,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                 .riscv64 => {
                     for (inst.inputs) |input, i| {
                         if (input.len < 3 or input[0] != '{' or input[input.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{}'", .{input});
+                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{s}'", .{input});
                         }
                         const reg_name = input[1 .. input.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         const arg = try self.resolveInst(inst.args[i]);
                         try self.genSetReg(inst.base.src, reg, arg);
                     }
@@ -2455,11 +2455,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
 
                     if (inst.output) |output| {
                         if (output.len < 4 or output[0] != '=' or output[1] != '{' or output[output.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{}'", .{output});
+                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{s}'", .{output});
                         }
                         const reg_name = output[2 .. output.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         return MCValue{ .register = reg };
                     } else {
                         return MCValue.none;
@@ -2468,11 +2468,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                 .x86_64, .i386 => {
                     for (inst.inputs) |input, i| {
                         if (input.len < 3 or input[0] != '{' or input[input.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{}'", .{input});
+                            return self.fail(inst.base.src, "unrecognized asm input constraint: '{s}'", .{input});
                         }
                         const reg_name = input[1 .. input.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         const arg = try self.resolveInst(inst.args[i]);
                         try self.genSetReg(inst.base.src, reg, arg);
                     }
@@ -2485,11 +2485,11 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
 
                     if (inst.output) |output| {
                         if (output.len < 4 or output[0] != '=' or output[1] != '{' or output[output.len - 1] != '}') {
-                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{}'", .{output});
+                            return self.fail(inst.base.src, "unrecognized asm output constraint: '{s}'", .{output});
                         }
                         const reg_name = output[2 .. output.len - 1];
                         const reg = parseRegName(reg_name) orelse
-                            return self.fail(inst.base.src, "unrecognized register: '{}'", .{reg_name});
+                            return self.fail(inst.base.src, "unrecognized register: '{s}'", .{reg_name});
                         return MCValue{ .register = reg };
                     } else {
                         return MCValue.none;
@@ -3417,7 +3417,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
                                             next_int_reg += 1;
                                         }
                                     },
-                                    else => return self.fail(src, "TODO implement function parameters of type {}", .{@tagName(ty.zigTypeTag())}),
+                                    else => return self.fail(src, "TODO implement function parameters of type {s}", .{@tagName(ty.zigTypeTag())}),
                                 }
                             }
                             result.stack_byte_count = next_stack_offset;
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index c6c29942d9..b97e1590e3 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -235,7 +235,7 @@ fn renderFunctionSignature(
                 try writer.writeAll(", ");
             }
             try renderType(ctx, writer, tv.ty.fnParamType(index));
-            try writer.print(" arg{}", .{index});
+            try writer.print(" arg{d}", .{index});
         }
     }
     try writer.writeByte(')');
@@ -481,8 +481,9 @@ fn genBinOp(ctx: *Context, file: *C, inst: *Inst.BinOp, operator: []const u8) !?
     const rhs = try ctx.resolveInst(inst.rhs);
     const writer = file.main.writer();
     const name = try ctx.name();
-    try renderTypeAndName(ctx, writer, inst.base.ty, name, .Const);
-    try writer.print(" = {s} {s} {s};\n", .{ lhs, operator, rhs });
+    try writer.writeAll(indentation ++ "const ");
+    try renderType(ctx, writer, inst.base.ty);
+    try writer.print(" {s} = {s} " ++ operator ++ " {s};\n", .{ name, lhs, rhs });
     return name;
 }
 
@@ -587,7 +588,7 @@ fn genAsm(ctx: *Context, file: *C, as: *Inst.Assembly) !?[]u8 {
             const arg = as.args[index];
             try writer.writeAll("register ");
             try renderType(ctx, writer, arg.ty);
-            try writer.print(" {}_constant __asm__(\"{}\") = ", .{ reg, reg });
+            try writer.print(" {s}_constant __asm__(\"{s}\") = ", .{ reg, reg });
             // TODO merge constant handling into inst_map as well
             if (arg.castTag(.constant)) |c| {
                 try renderValue(ctx, writer, arg.ty, c.val);
@@ -597,13 +598,13 @@ fn genAsm(ctx: *Context, file: *C, as: *Inst.Assembly) !?[]u8 {
                 if (!gop.found_existing) {
                     return ctx.fail(ctx.decl.src(), "Internal error in C backend: asm argument not found in inst_map", .{});
                 }
-                try writer.print("{};\n    ", .{gop.entry.value});
+                try writer.print("{s};\n    ", .{gop.entry.value});
             }
         } else {
             return ctx.fail(ctx.decl.src(), "TODO non-explicit inline asm regs", .{});
         }
     }
-    try writer.print("__asm {} (\"{}\"", .{ if (as.is_volatile) @as([]const u8, "volatile") else "", as.asm_source });
+    try writer.print("__asm {s} (\"{s}\"", .{ if (as.is_volatile) @as([]const u8, "volatile") else "", as.asm_source });
     if (as.output) |o| {
         return ctx.fail(ctx.decl.src(), "TODO inline asm output", .{});
     }
@@ -619,7 +620,7 @@ fn genAsm(ctx: *Context, file: *C, as: *Inst.Assembly) !?[]u8 {
                 if (index > 0) {
                     try writer.writeAll(", ");
                 }
-                try writer.print("\"\"({}_constant)", .{reg});
+                try writer.print("\"\"({s}_constant)", .{reg});
             } else {
                 // This is blocked by the earlier test
                 unreachable;
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
new file mode 100644
index 0000000000..3a1ebada3b
--- /dev/null
+++ b/src/codegen/llvm.zig
@@ -0,0 +1,125 @@
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+
+pub fn targetTriple(allocator: *Allocator, target: std.Target) ![]u8 {
+    const llvm_arch = switch (target.cpu.arch) {
+        .arm => "arm",
+        .armeb => "armeb",
+        .aarch64 => "aarch64",
+        .aarch64_be => "aarch64_be",
+        .aarch64_32 => "aarch64_32",
+        .arc => "arc",
+        .avr => "avr",
+        .bpfel => "bpfel",
+        .bpfeb => "bpfeb",
+        .hexagon => "hexagon",
+        .mips => "mips",
+        .mipsel => "mipsel",
+        .mips64 => "mips64",
+        .mips64el => "mips64el",
+        .msp430 => "msp430",
+        .powerpc => "powerpc",
+        .powerpc64 => "powerpc64",
+        .powerpc64le => "powerpc64le",
+        .r600 => "r600",
+        .amdgcn => "amdgcn",
+        .riscv32 => "riscv32",
+        .riscv64 => "riscv64",
+        .sparc => "sparc",
+        .sparcv9 => "sparcv9",
+        .sparcel => "sparcel",
+        .s390x => "s390x",
+        .tce => "tce",
+        .tcele => "tcele",
+        .thumb => "thumb",
+        .thumbeb => "thumbeb",
+        .i386 => "i386",
+        .x86_64 => "x86_64",
+        .xcore => "xcore",
+        .nvptx => "nvptx",
+        .nvptx64 => "nvptx64",
+        .le32 => "le32",
+        .le64 => "le64",
+        .amdil => "amdil",
+        .amdil64 => "amdil64",
+        .hsail => "hsail",
+        .hsail64 => "hsail64",
+        .spir => "spir",
+        .spir64 => "spir64",
+        .kalimba => "kalimba",
+        .shave => "shave",
+        .lanai => "lanai",
+        .wasm32 => "wasm32",
+        .wasm64 => "wasm64",
+        .renderscript32 => "renderscript32",
+        .renderscript64 => "renderscript64",
+        .ve => "ve",
+        .spu_2 => return error.LLVMBackendDoesNotSupportSPUMarkII,
+    };
+    // TODO Add a sub-arch for some architectures depending on CPU features.
+
+    const llvm_os = switch (target.os.tag) {
+        .freestanding => "unknown",
+        .ananas => "ananas",
+        .cloudabi => "cloudabi",
+        .dragonfly => "dragonfly",
+        .freebsd => "freebsd",
+        .fuchsia => "fuchsia",
+        .ios => "ios",
+        .kfreebsd => "kfreebsd",
+        .linux => "linux",
+        .lv2 => "lv2",
+        .macos => "macosx",
+        .netbsd => "netbsd",
+        .openbsd => "openbsd",
+        .solaris => "solaris",
+        .windows => "windows",
+        .haiku => "haiku",
+        .minix => "minix",
+        .rtems => "rtems",
+        .nacl => "nacl",
+        .cnk => "cnk",
+        .aix => "aix",
+        .cuda => "cuda",
+        .nvcl => "nvcl",
+        .amdhsa => "amdhsa",
+        .ps4 => "ps4",
+        .elfiamcu => "elfiamcu",
+        .tvos => "tvos",
+        .watchos => "watchos",
+        .mesa3d => "mesa3d",
+        .contiki => "contiki",
+        .amdpal => "amdpal",
+        .hermit => "hermit",
+        .hurd => "hurd",
+        .wasi => "wasi",
+        .emscripten => "emscripten",
+        .uefi => "windows",
+        .other => "unknown",
+    };
+
+    const llvm_abi = switch (target.abi) {
+        .none => "unknown",
+        .gnu => "gnu",
+        .gnuabin32 => "gnuabin32",
+        .gnuabi64 => "gnuabi64",
+        .gnueabi => "gnueabi",
+        .gnueabihf => "gnueabihf",
+        .gnux32 => "gnux32",
+        .code16 => "code16",
+        .eabi => "eabi",
+        .eabihf => "eabihf",
+        .android => "android",
+        .musl => "musl",
+        .musleabi => "musleabi",
+        .musleabihf => "musleabihf",
+        .msvc => "msvc",
+        .itanium => "itanium",
+        .cygnus => "cygnus",
+        .coreclr => "coreclr",
+        .simulator => "simulator",
+        .macabi => "macabi",
+    };
+
+    return std.fmt.allocPrint(allocator, "{s}-unknown-{s}-{s}", .{ llvm_arch, llvm_os, llvm_abi });
+}
diff --git a/src/glibc.zig b/src/glibc.zig
index 0c27872720..f69dd11ada 100644
--- a/src/glibc.zig
+++ b/src/glibc.zig
@@ -72,7 +72,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
     errdefer version_table.deinit(gpa);
 
     var glibc_dir = zig_lib_dir.openDir("libc" ++ path.sep_str ++ "glibc", .{}) catch |err| {
-        std.log.err("unable to open glibc dir: {}", .{@errorName(err)});
+        std.log.err("unable to open glibc dir: {s}", .{@errorName(err)});
         return error.ZigInstallationCorrupt;
     };
     defer glibc_dir.close();
@@ -81,7 +81,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
     const vers_txt_contents = glibc_dir.readFileAlloc(gpa, "vers.txt", max_txt_size) catch |err| switch (err) {
         error.OutOfMemory => return error.OutOfMemory,
         else => {
-            std.log.err("unable to read vers.txt: {}", .{@errorName(err)});
+            std.log.err("unable to read vers.txt: {s}", .{@errorName(err)});
             return error.ZigInstallationCorrupt;
         },
     };
@@ -91,7 +91,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
     const fns_txt_contents = glibc_dir.readFileAlloc(arena, "fns.txt", max_txt_size) catch |err| switch (err) {
         error.OutOfMemory => return error.OutOfMemory,
         else => {
-            std.log.err("unable to read fns.txt: {}", .{@errorName(err)});
+            std.log.err("unable to read fns.txt: {s}", .{@errorName(err)});
             return error.ZigInstallationCorrupt;
         },
     };
@@ -99,7 +99,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
     const abi_txt_contents = glibc_dir.readFileAlloc(gpa, "abi.txt", max_txt_size) catch |err| switch (err) {
         error.OutOfMemory => return error.OutOfMemory,
         else => {
-            std.log.err("unable to read abi.txt: {}", .{@errorName(err)});
+            std.log.err("unable to read abi.txt: {s}", .{@errorName(err)});
             return error.ZigInstallationCorrupt;
         },
     };
@@ -116,7 +116,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
             }
             const adjusted_line = line[prefix.len..];
             const ver = std.builtin.Version.parse(adjusted_line) catch |err| {
-                std.log.err("vers.txt:{}: unable to parse glibc version '{}': {}", .{ line_i, line, @errorName(err) });
+                std.log.err("vers.txt:{}: unable to parse glibc version '{s}': {s}", .{ line_i, line, @errorName(err) });
                 return error.ZigInstallationCorrupt;
             };
             try all_versions.append(arena, ver);
@@ -136,7 +136,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
                 return error.ZigInstallationCorrupt;
             };
             const lib = findLib(lib_name) orelse {
-                std.log.err("fns.txt:{}: unknown library name: {}", .{ line_i, lib_name });
+                std.log.err("fns.txt:{}: unknown library name: {s}", .{ line_i, lib_name });
                 return error.ZigInstallationCorrupt;
             };
             try all_functions.append(arena, .{
@@ -170,15 +170,15 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
                         return error.ZigInstallationCorrupt;
                     };
                     const arch_tag = std.meta.stringToEnum(std.Target.Cpu.Arch, arch_name) orelse {
-                        std.log.err("abi.txt:{}: unrecognized arch: '{}'", .{ line_i, arch_name });
+                        std.log.err("abi.txt:{}: unrecognized arch: '{s}'", .{ line_i, arch_name });
                         return error.ZigInstallationCorrupt;
                     };
                     if (!mem.eql(u8, os_name, "linux")) {
-                        std.log.err("abi.txt:{}: expected OS 'linux', found '{}'", .{ line_i, os_name });
+                        std.log.err("abi.txt:{}: expected OS 'linux', found '{s}'", .{ line_i, os_name });
                         return error.ZigInstallationCorrupt;
                     }
                     const abi_tag = std.meta.stringToEnum(std.Target.Abi, abi_name) orelse {
-                        std.log.err("abi.txt:{}: unrecognized ABI: '{}'", .{ line_i, abi_name });
+                        std.log.err("abi.txt:{}: unrecognized ABI: '{s}'", .{ line_i, abi_name });
                         return error.ZigInstallationCorrupt;
                     };
 
@@ -211,7 +211,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
                     }
                     const version_index = std.fmt.parseInt(u8, version_index_string, 10) catch |err| {
                         // If this happens with legit data, increase the size of the integer type in the struct.
-                        std.log.err("abi.txt:{}: unable to parse version: {}", .{ line_i, @errorName(err) });
+                        std.log.err("abi.txt:{}: unable to parse version: {s}", .{ line_i, @errorName(err) });
                         return error.ZigInstallationCorrupt;
                     };
 
@@ -531,7 +531,7 @@ fn add_include_dirs(comp: *Compilation, arena: *Allocator, args: *std.ArrayList(
     try args.append(try path.join(arena, &[_][]const u8{ comp.zig_lib_directory.path.?, lib_libc ++ "glibc" }));
 
     try args.append("-I");
-    try args.append(try std.fmt.allocPrint(arena, "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{}-{}-{}", .{
+    try args.append(try std.fmt.allocPrint(arena, "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-{s}-{s}", .{
         comp.zig_lib_directory.path.?, @tagName(arch), @tagName(target.os.tag), @tagName(target.abi),
     }));
 
@@ -539,7 +539,7 @@ fn add_include_dirs(comp: *Compilation, arena: *Allocator, args: *std.ArrayList(
     try args.append(try lib_path(comp, arena, lib_libc ++ "include" ++ s ++ "generic-glibc"));
 
     try args.append("-I");
-    try args.append(try std.fmt.allocPrint(arena, "{}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{}-linux-any", .{
+    try args.append(try std.fmt.allocPrint(arena, "{s}" ++ s ++ "libc" ++ s ++ "include" ++ s ++ "{s}-linux-any", .{
         comp.zig_lib_directory.path.?, @tagName(arch),
     }));
 
@@ -881,7 +881,7 @@ pub fn buildSharedObjects(comp: *Compilation) !void {
         if (o_directory.handle.createFile(ok_basename, .{})) |file| {
             file.close();
         } else |err| {
-            std.log.warn("glibc shared objects: failed to mark completion: {}", .{@errorName(err)});
+            std.log.warn("glibc shared objects: failed to mark completion: {s}", .{@errorName(err)});
         }
     }
 
diff --git a/src/libc_installation.zig b/src/libc_installation.zig
index 0b1029eeb8..cc96146e0b 100644
--- a/src/libc_installation.zig
+++ b/src/libc_installation.zig
@@ -83,7 +83,7 @@ pub const LibCInstallation = struct {
         }
         inline for (fields) |field, i| {
             if (!found_keys[i].found) {
-                log.err("missing field: {}\n", .{field.name});
+                log.err("missing field: {s}\n", .{field.name});
                 return error.ParseError;
             }
         }
@@ -96,18 +96,18 @@ pub const LibCInstallation = struct {
             return error.ParseError;
         }
         if (self.crt_dir == null and !is_darwin) {
-            log.err("crt_dir may not be empty for {}\n", .{@tagName(Target.current.os.tag)});
+            log.err("crt_dir may not be empty for {s}\n", .{@tagName(Target.current.os.tag)});
             return error.ParseError;
         }
         if (self.msvc_lib_dir == null and is_windows and !is_gnu) {
-            log.err("msvc_lib_dir may not be empty for {}-{}\n", .{
+            log.err("msvc_lib_dir may not be empty for {s}-{s}\n", .{
                 @tagName(Target.current.os.tag),
                 @tagName(Target.current.abi),
             });
             return error.ParseError;
         }
         if (self.kernel32_lib_dir == null and is_windows and !is_gnu) {
-            log.err("kernel32_lib_dir may not be empty for {}-{}\n", .{
+            log.err("kernel32_lib_dir may not be empty for {s}-{s}\n", .{
                 @tagName(Target.current.os.tag),
                 @tagName(Target.current.abi),
             });
@@ -128,25 +128,25 @@ pub const LibCInstallation = struct {
         try out.print(
             \\# The directory that contains `stdlib.h`.
             \\# On POSIX-like systems, include directories be found with: `cc -E -Wp,-v -xc /dev/null`
-            \\include_dir={}
+            \\include_dir={s}
             \\
             \\# The system-specific include directory. May be the same as `include_dir`.
             \\# On Windows it's the directory that includes `vcruntime.h`.
             \\# On POSIX it's the directory that includes `sys/errno.h`.
-            \\sys_include_dir={}
+            \\sys_include_dir={s}
             \\
             \\# The directory that contains `crt1.o` or `crt2.o`.
             \\# On POSIX, can be found with `cc -print-file-name=crt1.o`.
             \\# Not needed when targeting MacOS.
-            \\crt_dir={}
+            \\crt_dir={s}
             \\
             \\# The directory that contains `vcruntime.lib`.
             \\# Only needed when targeting MSVC on Windows.
-            \\msvc_lib_dir={}
+            \\msvc_lib_dir={s}
             \\
             \\# The directory that contains `kernel32.lib`.
             \\# Only needed when targeting MSVC on Windows.
-            \\kernel32_lib_dir={}
+            \\kernel32_lib_dir={s}
             \\
         , .{
             include_dir,
@@ -338,7 +338,7 @@ pub const LibCInstallation = struct {
 
         for (searches) |search| {
             result_buf.shrink(0);
-            try result_buf.outStream().print("{}\\Include\\{}\\ucrt", .{ search.path, search.version });
+            try result_buf.outStream().print("{s}\\Include\\{s}\\ucrt", .{ search.path, search.version });
 
             var dir = fs.cwd().openDir(result_buf.items, .{}) catch |err| switch (err) {
                 error.FileNotFound,
@@ -384,7 +384,7 @@ pub const LibCInstallation = struct {
 
         for (searches) |search| {
             result_buf.shrink(0);
-            try result_buf.outStream().print("{}\\Lib\\{}\\ucrt\\{}", .{ search.path, search.version, arch_sub_dir });
+            try result_buf.outStream().print("{s}\\Lib\\{s}\\ucrt\\{s}", .{ search.path, search.version, arch_sub_dir });
 
             var dir = fs.cwd().openDir(result_buf.items, .{}) catch |err| switch (err) {
                 error.FileNotFound,
@@ -439,7 +439,7 @@ pub const LibCInstallation = struct {
         for (searches) |search| {
             result_buf.shrink(0);
             const stream = result_buf.outStream();
-            try stream.print("{}\\Lib\\{}\\um\\{}", .{ search.path, search.version, arch_sub_dir });
+            try stream.print("{s}\\Lib\\{s}\\um\\{s}", .{ search.path, search.version, arch_sub_dir });
 
             var dir = fs.cwd().openDir(result_buf.items, .{}) catch |err| switch (err) {
                 error.FileNotFound,
@@ -520,7 +520,7 @@ fn ccPrintFileName(args: CCPrintFileNameOptions) ![:0]u8 {
     const allocator = args.allocator;
 
     const cc_exe = std.os.getenvZ("CC") orelse default_cc_exe;
-    const arg1 = try std.fmt.allocPrint(allocator, "-print-file-name={}", .{args.search_basename});
+    const arg1 = try std.fmt.allocPrint(allocator, "-print-file-name={s}", .{args.search_basename});
     defer allocator.free(arg1);
     const argv = [_][]const u8{ cc_exe, arg1 };
 
@@ -584,17 +584,17 @@ fn printVerboseInvocation(
     if (!verbose) return;
 
     if (search_basename) |s| {
-        std.debug.warn("Zig attempted to find the file '{}' by executing this command:\n", .{s});
+        std.debug.warn("Zig attempted to find the file '{s}' by executing this command:\n", .{s});
     } else {
         std.debug.warn("Zig attempted to find the path to native system libc headers by executing this command:\n", .{});
     }
     for (argv) |arg, i| {
         if (i != 0) std.debug.warn(" ", .{});
-        std.debug.warn("{}", .{arg});
+        std.debug.warn("{s}", .{arg});
     }
     std.debug.warn("\n", .{});
     if (stderr) |s| {
-        std.debug.warn("Output:\n==========\n{}\n==========\n", .{s});
+        std.debug.warn("Output:\n==========\n{s}\n==========\n", .{s});
     }
 }
 
diff --git a/src/link.zig b/src/link.zig
index 468f23bffd..92702c7973 100644
--- a/src/link.zig
+++ b/src/link.zig
@@ -560,9 +560,9 @@ pub const File = struct {
         const full_out_path_z = try arena.dupeZ(u8, full_out_path);
 
         if (base.options.verbose_link) {
-            std.debug.print("ar rcs {}", .{full_out_path_z});
+            std.debug.print("ar rcs {s}", .{full_out_path_z});
             for (object_files.items) |arg| {
-                std.debug.print(" {}", .{arg});
+                std.debug.print(" {s}", .{arg});
             }
             std.debug.print("\n", .{});
         }
@@ -574,11 +574,11 @@ pub const File = struct {
 
         if (!base.options.disable_lld_caching) {
             Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
-                log.warn("failed to save archive hash digest file: {}", .{@errorName(err)});
+                log.warn("failed to save archive hash digest file: {s}", .{@errorName(err)});
             };
 
             man.writeManifest() catch |err| {
-                log.warn("failed to write cache manifest when archiving: {}", .{@errorName(err)});
+                log.warn("failed to write cache manifest when archiving: {s}", .{@errorName(err)});
             };
 
             base.lock = man.toOwnedLock();
diff --git a/src/link/C.zig b/src/link/C.zig
index 1059e52115..3ac9db717f 100644
--- a/src/link/C.zig
+++ b/src/link/C.zig
@@ -111,8 +111,11 @@ pub fn flushModule(self: *C, comp: *Compilation) !void {
     if (self.header.buf.items.len > 0) {
         try writer.writeByte('\n');
     }
+    if (self.header.items.len > 0) {
+        try writer.print("{s}\n", .{self.header.items});
+    }
     if (self.constants.items.len > 0) {
-        try writer.print("{}\n", .{self.constants.items});
+        try writer.print("{s}\n", .{self.constants.items});
     }
     if (self.main.items.len > 1) {
         const last_two = self.main.items[self.main.items.len - 2 ..];
diff --git a/src/link/Coff.zig b/src/link/Coff.zig
index 096fa2cd0b..a3cb5cc4c7 100644
--- a/src/link/Coff.zig
+++ b/src/link/Coff.zig
@@ -686,7 +686,7 @@ pub fn updateDecl(self: *Coff, module: *Module, decl: *Module.Decl) !void {
         if (need_realloc) {
             const curr_vaddr = self.getDeclVAddr(decl);
             const vaddr = try self.growTextBlock(&decl.link.coff, code.len, required_alignment);
-            log.debug("growing {} from 0x{x} to 0x{x}\n", .{ decl.name, curr_vaddr, vaddr });
+            log.debug("growing {s} from 0x{x} to 0x{x}\n", .{ decl.name, curr_vaddr, vaddr });
             if (vaddr != curr_vaddr) {
                 log.debug("  (writing new offset table entry)\n", .{});
                 self.offset_table.items[decl.link.coff.offset_table_index] = vaddr;
@@ -697,7 +697,7 @@ pub fn updateDecl(self: *Coff, module: *Module, decl: *Module.Decl) !void {
         }
     } else {
         const vaddr = try self.allocateTextBlock(&decl.link.coff, code.len, required_alignment);
-        log.debug("allocated text block for {} at 0x{x} (size: {Bi})\n", .{ mem.spanZ(decl.name), vaddr, code.len });
+        log.debug("allocated text block for {s} at 0x{x} (size: {Bi})\n", .{ mem.spanZ(decl.name), vaddr, code.len });
         errdefer self.freeTextBlock(&decl.link.coff);
         self.offset_table.items[decl.link.coff.offset_table_index] = vaddr;
         try self.writeOffsetTableEntry(decl.link.coff.offset_table_index);
@@ -880,7 +880,7 @@ fn linkWithLLD(self: *Coff, comp: *Compilation) !void {
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("COFF LLD new_digest={} error: {}", .{ digest, @errorName(err) });
+            log.debug("COFF LLD new_digest={} error: {s}", .{ digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -1236,11 +1236,11 @@ fn linkWithLLD(self: *Coff, comp: *Compilation) !void {
         // Update the file with the digest. If it fails we can continue; it only
         // means that the next invocation will have an unnecessary cache miss.
         Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
-            log.warn("failed to save linking hash digest file: {}", .{@errorName(err)});
+            log.warn("failed to save linking hash digest file: {s}", .{@errorName(err)});
         };
         // Again failure here only means an unnecessary cache miss.
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest when linking: {}", .{@errorName(err)});
+            log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
         };
         // We hang on to this lock so that the output file path can be used without
         // other processes clobbering it.
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 4b2b95fc72..2db15ae280 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -1362,7 +1362,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation) !void {
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("ELF LLD new_digest={} error: {}", .{ digest, @errorName(err) });
+            log.debug("ELF LLD new_digest={} error: {s}", .{ digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -1396,7 +1396,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation) !void {
 
     if (self.base.options.output_mode == .Exe) {
         try argv.append("-z");
-        try argv.append(try std.fmt.allocPrint(arena, "stack-size={}", .{stack_size}));
+        try argv.append(try std.fmt.allocPrint(arena, "stack-size={d}", .{stack_size}));
     }
 
     if (self.base.options.image_base_override) |image_base| {
@@ -1438,7 +1438,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation) !void {
     if (getLDMOption(target)) |ldm| {
         // Any target ELF will use the freebsd osabi if suffixed with "_fbsd".
         const arg = if (target.os.tag == .freebsd)
-            try std.fmt.allocPrint(arena, "{}_fbsd", .{ldm})
+            try std.fmt.allocPrint(arena, "{s}_fbsd", .{ldm})
         else
             ldm;
         try argv.append("-m");
@@ -1599,7 +1599,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation) !void {
             // (the check for that needs to be earlier), but they could be full paths to .so files, in which
             // case we want to avoid prepending "-l".
             const ext = Compilation.classifyFileExt(link_lib);
-            const arg = if (ext == .shared_library) link_lib else try std.fmt.allocPrint(arena, "-l{}", .{link_lib});
+            const arg = if (ext == .shared_library) link_lib else try std.fmt.allocPrint(arena, "-l{s}", .{link_lib});
             argv.appendAssumeCapacity(arg);
         }
 
@@ -1733,11 +1733,11 @@ fn linkWithLLD(self: *Elf, comp: *Compilation) !void {
         // Update the file with the digest. If it fails we can continue; it only
         // means that the next invocation will have an unnecessary cache miss.
         Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
-            log.warn("failed to save linking hash digest file: {}", .{@errorName(err)});
+            log.warn("failed to save linking hash digest file: {s}", .{@errorName(err)});
         };
         // Again failure here only means an unnecessary cache miss.
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest when linking: {}", .{@errorName(err)});
+            log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
         };
         // We hang on to this lock so that the output file path can be used without
         // other processes clobbering it.
@@ -2082,10 +2082,10 @@ pub fn allocateDeclIndexes(self: *Elf, decl: *Module.Decl) !void {
     try self.offset_table.ensureCapacity(self.base.allocator, self.offset_table.items.len + 1);
 
     if (self.local_symbol_free_list.popOrNull()) |i| {
-        log.debug("reusing symbol index {} for {}\n", .{ i, decl.name });
+        log.debug("reusing symbol index {} for {s}\n", .{ i, decl.name });
         decl.link.elf.local_sym_index = i;
     } else {
-        log.debug("allocating symbol index {} for {}\n", .{ self.local_symbols.items.len, decl.name });
+        log.debug("allocating symbol index {} for {s}\n", .{ self.local_symbols.items.len, decl.name });
         decl.link.elf.local_sym_index = @intCast(u32, self.local_symbols.items.len);
         _ = self.local_symbols.addOneAssumeCapacity();
     }
@@ -2182,7 +2182,7 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
         if (zir_dumps.len != 0) {
             for (zir_dumps) |fn_name| {
                 if (mem.eql(u8, mem.spanZ(decl.name), fn_name)) {
-                    std.debug.print("\n{}\n", .{decl.name});
+                    std.debug.print("\n{s}\n", .{decl.name});
                     typed_value.val.castTag(.function).?.data.dump(module.*);
                 }
             }
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index 6abbae2c26..d4a61c8149 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -520,7 +520,7 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("MachO LLD new_digest={} error: {}", .{ digest, @errorName(err) });
+            log.debug("MachO LLD new_digest={} error: {s}", .{ digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -706,7 +706,7 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
             // (the check for that needs to be earlier), but they could be full paths to .dylib files, in which
             // case we want to avoid prepending "-l".
             const ext = Compilation.classifyFileExt(link_lib);
-            const arg = if (ext == .shared_library) link_lib else try std.fmt.allocPrint(arena, "-l{}", .{link_lib});
+            const arg = if (ext == .shared_library) link_lib else try std.fmt.allocPrint(arena, "-l{s}", .{link_lib});
             argv.appendAssumeCapacity(arg);
         }
 
@@ -759,15 +759,15 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
                 self.base.allocator.free(result.stderr);
             }
             if (result.stdout.len != 0) {
-                log.warn("unexpected LD stdout: {}", .{result.stdout});
+                log.warn("unexpected LD stdout: {s}", .{result.stdout});
             }
             if (result.stderr.len != 0) {
-                log.warn("unexpected LD stderr: {}", .{result.stderr});
+                log.warn("unexpected LD stderr: {s}", .{result.stderr});
             }
             if (result.term != .Exited or result.term.Exited != 0) {
                 // TODO parse this output and surface with the Compilation API rather than
                 // directly outputting to stderr here.
-                log.err("{}", .{result.stderr});
+                log.err("{s}", .{result.stderr});
                 return error.LDReportedFailure;
             }
         } else {
@@ -980,11 +980,11 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
         // Update the file with the digest. If it fails we can continue; it only
         // means that the next invocation will have an unnecessary cache miss.
         Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
-            log.warn("failed to save linking hash digest file: {}", .{@errorName(err)});
+            log.warn("failed to save linking hash digest file: {s}", .{@errorName(err)});
         };
         // Again failure here only means an unnecessary cache miss.
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest when linking: {}", .{@errorName(err)});
+            log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
         };
         // We hang on to this lock so that the output file path can be used without
         // other processes clobbering it.
@@ -1088,10 +1088,10 @@ pub fn allocateDeclIndexes(self: *MachO, decl: *Module.Decl) !void {
     try self.offset_table.ensureCapacity(self.base.allocator, self.offset_table.items.len + 1);
 
     if (self.local_symbol_free_list.popOrNull()) |i| {
-        log.debug("reusing symbol index {} for {}", .{ i, decl.name });
+        log.debug("reusing symbol index {d} for {s}", .{ i, decl.name });
         decl.link.macho.local_sym_index = i;
     } else {
-        log.debug("allocating symbol index {} for {}", .{ self.local_symbols.items.len, decl.name });
+        log.debug("allocating symbol index {d} for {s}", .{ self.local_symbols.items.len, decl.name });
         decl.link.macho.local_sym_index = @intCast(u32, self.local_symbols.items.len);
         _ = self.local_symbols.addOneAssumeCapacity();
     }
@@ -1165,7 +1165,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
         const need_realloc = code.len > capacity or !mem.isAlignedGeneric(u64, symbol.n_value, required_alignment);
         if (need_realloc) {
             const vaddr = try self.growTextBlock(&decl.link.macho, code.len, required_alignment);
-            log.debug("growing {} from 0x{x} to 0x{x}", .{ decl.name, symbol.n_value, vaddr });
+            log.debug("growing {s} from 0x{x} to 0x{x}", .{ decl.name, symbol.n_value, vaddr });
             if (vaddr != symbol.n_value) {
                 symbol.n_value = vaddr;
                 log.debug(" (writing new offset table entry)", .{});
@@ -1188,7 +1188,7 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
         const decl_name = mem.spanZ(decl.name);
         const name_str_index = try self.makeString(decl_name);
         const addr = try self.allocateTextBlock(&decl.link.macho, code.len, required_alignment);
-        log.debug("allocated text block for {} at 0x{x}", .{ decl_name, addr });
+        log.debug("allocated text block for {s} at 0x{x}", .{ decl_name, addr });
         errdefer self.freeTextBlock(&decl.link.macho);
 
         symbol.* = .{
diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig
index 374fa2230b..cbb3e83147 100644
--- a/src/link/Wasm.zig
+++ b/src/link/Wasm.zig
@@ -321,7 +321,7 @@ fn linkWithLLD(self: *Wasm, comp: *Compilation) !void {
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("WASM LLD new_digest={} error: {}", .{ digest, @errorName(err) });
+            log.debug("WASM LLD new_digest={} error: {s}", .{ digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -463,11 +463,11 @@ fn linkWithLLD(self: *Wasm, comp: *Compilation) !void {
         // Update the file with the digest. If it fails we can continue; it only
         // means that the next invocation will have an unnecessary cache miss.
         Cache.writeSmallFile(directory.handle, id_symlink_basename, &digest) catch |err| {
-            log.warn("failed to save linking hash digest symlink: {}", .{@errorName(err)});
+            log.warn("failed to save linking hash digest symlink: {s}", .{@errorName(err)});
         };
         // Again failure here only means an unnecessary cache miss.
         man.writeManifest() catch |err| {
-            log.warn("failed to write cache manifest when linking: {}", .{@errorName(err)});
+            log.warn("failed to write cache manifest when linking: {s}", .{@errorName(err)});
         };
         // We hang on to this lock so that the output file path can be used without
         // other processes clobbering it.
diff --git a/src/main.zig b/src/main.zig
index 98b19cc3ea..7d03ea956f 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -118,7 +118,7 @@ pub fn main() anyerror!void {
 
 pub fn mainArgs(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !void {
     if (args.len <= 1) {
-        std.log.info("{}", .{usage});
+        std.log.info("{s}", .{usage});
         fatal("expected command argument", .{});
     }
 
@@ -204,8 +204,8 @@ pub fn mainArgs(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
     } else if (mem.eql(u8, cmd, "help") or mem.eql(u8, cmd, "-h") or mem.eql(u8, cmd, "--help")) {
         try io.getStdOut().writeAll(usage);
     } else {
-        std.log.info("{}", .{usage});
-        fatal("unknown command: {}", .{args[1]});
+        std.log.info("{s}", .{usage});
+        fatal("unknown command: {s}", .{args[1]});
     }
 }
 
@@ -615,7 +615,7 @@ fn buildOutputType(
                             fatal("unexpected end-of-parameter mark: --", .{});
                         }
                     } else if (mem.eql(u8, arg, "--pkg-begin")) {
-                        if (i + 2 >= args.len) fatal("Expected 2 arguments after {}", .{arg});
+                        if (i + 2 >= args.len) fatal("Expected 2 arguments after {s}", .{arg});
                         i += 1;
                         const pkg_name = args[i];
                         i += 1;
@@ -635,7 +635,7 @@ fn buildOutputType(
                         cur_pkg = cur_pkg.parent orelse
                             fatal("encountered --pkg-end with no matching --pkg-begin", .{});
                     } else if (mem.eql(u8, arg, "--main-pkg-path")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         main_pkg_path = args[i];
                     } else if (mem.eql(u8, arg, "-cflags")) {
@@ -653,10 +653,10 @@ fn buildOutputType(
                         i += 1;
                         const next_arg = args[i];
                         color = std.meta.stringToEnum(Color, next_arg) orelse {
-                            fatal("expected [auto|on|off] after --color, found '{}'", .{next_arg});
+                            fatal("expected [auto|on|off] after --color, found '{s}'", .{next_arg});
                         };
                     } else if (mem.eql(u8, arg, "--subsystem")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         if (mem.eql(u8, args[i], "console")) {
                             subsystem = .Console;
@@ -689,51 +689,51 @@ fn buildOutputType(
                             });
                         }
                     } else if (mem.eql(u8, arg, "-O")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         optimize_mode_string = args[i];
                     } else if (mem.eql(u8, arg, "--stack")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         stack_size_override = std.fmt.parseUnsigned(u64, args[i], 0) catch |err| {
                             fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
                         };
                     } else if (mem.eql(u8, arg, "--image-base")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         image_base_override = std.fmt.parseUnsigned(u64, args[i], 0) catch |err| {
                             fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
                         };
                     } else if (mem.eql(u8, arg, "--name")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         provided_name = args[i];
                     } else if (mem.eql(u8, arg, "-rpath")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try rpath_list.append(args[i]);
                     } else if (mem.eql(u8, arg, "--library-directory") or mem.eql(u8, arg, "-L")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try lib_dirs.append(args[i]);
                     } else if (mem.eql(u8, arg, "-F")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try framework_dirs.append(args[i]);
                     } else if (mem.eql(u8, arg, "-framework")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try frameworks.append(args[i]);
                     } else if (mem.eql(u8, arg, "-T") or mem.eql(u8, arg, "--script")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         linker_script = args[i];
                     } else if (mem.eql(u8, arg, "--version-script")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         version_script = args[i];
                     } else if (mem.eql(u8, arg, "--library") or mem.eql(u8, arg, "-l")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         // We don't know whether this library is part of libc or libc++ until we resolve the target.
                         // So we simply append to the list for now.
                         i += 1;
@@ -743,7 +743,7 @@ fn buildOutputType(
                         mem.eql(u8, arg, "-I") or
                         mem.eql(u8, arg, "-dirafter"))
                     {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try clang_argv.append(arg);
                         try clang_argv.append(args[i]);
@@ -753,19 +753,19 @@ fn buildOutputType(
                         }
                         i += 1;
                         version = std.builtin.Version.parse(args[i]) catch |err| {
-                            fatal("unable to parse --version '{}': {}", .{ args[i], @errorName(err) });
+                            fatal("unable to parse --version '{s}': {s}", .{ args[i], @errorName(err) });
                         };
                         have_version = true;
                     } else if (mem.eql(u8, arg, "-target")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         target_arch_os_abi = args[i];
                     } else if (mem.eql(u8, arg, "-mcpu")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         target_mcpu = args[i];
                     } else if (mem.eql(u8, arg, "-mcmodel")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         machine_code_model = parseCodeModel(args[i]);
                     } else if (mem.startsWith(u8, arg, "-ofmt=")) {
@@ -777,35 +777,35 @@ fn buildOutputType(
                     } else if (mem.startsWith(u8, arg, "-O")) {
                         optimize_mode_string = arg["-O".len..];
                     } else if (mem.eql(u8, arg, "--dynamic-linker")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         target_dynamic_linker = args[i];
                     } else if (mem.eql(u8, arg, "--libc")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         libc_paths_file = args[i];
                     } else if (mem.eql(u8, arg, "--test-filter")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         test_filter = args[i];
                     } else if (mem.eql(u8, arg, "--test-name-prefix")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         test_name_prefix = args[i];
                     } else if (mem.eql(u8, arg, "--test-cmd")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         try test_exec_args.append(args[i]);
                     } else if (mem.eql(u8, arg, "--cache-dir")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         override_local_cache_dir = args[i];
                     } else if (mem.eql(u8, arg, "--global-cache-dir")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         override_global_cache_dir = args[i];
                     } else if (mem.eql(u8, arg, "--override-lib-dir")) {
-                        if (i + 1 >= args.len) fatal("expected parameter after {}", .{arg});
+                        if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         override_lib_dir = args[i];
                     } else if (mem.eql(u8, arg, "-fcompiler-rt")) {
@@ -968,7 +968,7 @@ fn buildOutputType(
                     {
                         try clang_argv.append(arg);
                     } else {
-                        fatal("unrecognized parameter: '{}'", .{arg});
+                        fatal("unrecognized parameter: '{s}'", .{arg});
                     }
                 } else switch (Compilation.classifyFileExt(arg)) {
                     .object, .static_library, .shared_library => {
@@ -982,19 +982,19 @@ fn buildOutputType(
                     },
                     .zig, .zir => {
                         if (root_src_file) |other| {
-                            fatal("found another zig file '{}' after root source file '{}'", .{ arg, other });
+                            fatal("found another zig file '{s}' after root source file '{s}'", .{ arg, other });
                         } else {
                             root_src_file = arg;
                         }
                     },
                     .unknown => {
-                        fatal("unrecognized file extension of parameter '{}'", .{arg});
+                        fatal("unrecognized file extension of parameter '{s}'", .{arg});
                     },
                 }
             }
             if (optimize_mode_string) |s| {
                 optimize_mode = std.meta.stringToEnum(std.builtin.Mode, s) orelse
-                    fatal("unrecognized optimization mode: '{}'", .{s});
+                    fatal("unrecognized optimization mode: '{s}'", .{s});
             }
         },
         .cc, .cpp => {
@@ -1018,7 +1018,7 @@ fn buildOutputType(
             var it = ClangArgIterator.init(arena, all_args);
             while (it.has_next) {
                 it.next() catch |err| {
-                    fatal("unable to parse command line parameters: {}", .{@errorName(err)});
+                    fatal("unable to parse command line parameters: {s}", .{@errorName(err)});
                 };
                 switch (it.zig_equivalent) {
                     .target => target_arch_os_abi = it.only_arg, // example: -target riscv64-linux-unknown
@@ -1038,7 +1038,7 @@ fn buildOutputType(
                             },
                             .zig, .zir => {
                                 if (root_src_file) |other| {
-                                    fatal("found another zig file '{}' after root source file '{}'", .{ it.only_arg, other });
+                                    fatal("found another zig file '{s}' after root source file '{s}'", .{ it.only_arg, other });
                                 } else {
                                     root_src_file = it.only_arg;
                                 }
@@ -1153,7 +1153,7 @@ fn buildOutputType(
                 if (mem.eql(u8, arg, "-soname")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     const name = linker_args.items[i];
                     soname = .{ .yes = name };
@@ -1185,7 +1185,7 @@ fn buildOutputType(
                 } else if (mem.eql(u8, arg, "-rpath")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     try rpath_list.append(linker_args.items[i]);
                 } else if (mem.eql(u8, arg, "-I") or
@@ -1194,7 +1194,7 @@ fn buildOutputType(
                 {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     target_dynamic_linker = linker_args.items[i];
                 } else if (mem.eql(u8, arg, "-E") or
@@ -1205,7 +1205,7 @@ fn buildOutputType(
                 } else if (mem.eql(u8, arg, "--version-script")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     version_script = linker_args.items[i];
                 } else if (mem.startsWith(u8, arg, "-O")) {
@@ -1227,7 +1227,7 @@ fn buildOutputType(
                 } else if (mem.eql(u8, arg, "-z")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     const z_arg = linker_args.items[i];
                     if (mem.eql(u8, z_arg, "nodelete")) {
@@ -1235,44 +1235,44 @@ fn buildOutputType(
                     } else if (mem.eql(u8, z_arg, "defs")) {
                         linker_z_defs = true;
                     } else {
-                        warn("unsupported linker arg: -z {}", .{z_arg});
+                        warn("unsupported linker arg: -z {s}", .{z_arg});
                     }
                 } else if (mem.eql(u8, arg, "--major-image-version")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     version.major = std.fmt.parseUnsigned(u32, linker_args.items[i], 10) catch |err| {
-                        fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                        fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                     };
                     have_version = true;
                 } else if (mem.eql(u8, arg, "--minor-image-version")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     version.minor = std.fmt.parseUnsigned(u32, linker_args.items[i], 10) catch |err| {
-                        fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                        fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                     };
                     have_version = true;
                 } else if (mem.eql(u8, arg, "--stack")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     stack_size_override = std.fmt.parseUnsigned(u64, linker_args.items[i], 0) catch |err| {
-                        fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                        fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                     };
                 } else if (mem.eql(u8, arg, "--image-base")) {
                     i += 1;
                     if (i >= linker_args.items.len) {
-                        fatal("expected linker arg after '{}'", .{arg});
+                        fatal("expected linker arg after '{s}'", .{arg});
                     }
                     image_base_override = std.fmt.parseUnsigned(u64, linker_args.items[i], 0) catch |err| {
-                        fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                        fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                     };
                 } else {
-                    warn("unsupported linker arg: {}", .{arg});
+                    warn("unsupported linker arg: {s}", .{arg});
                 }
             }
 
@@ -1328,7 +1328,7 @@ fn buildOutputType(
     }
 
     if (arg_mode == .translate_c and c_source_files.items.len != 1) {
-        fatal("translate-c expects exactly 1 source file (found {})", .{c_source_files.items.len});
+        fatal("translate-c expects exactly 1 source file (found {d})", .{c_source_files.items.len});
     }
 
     if (root_src_file == null and arg_mode == .zig_test) {
@@ -1373,25 +1373,25 @@ fn buildOutputType(
             help: {
                 var help_text = std.ArrayList(u8).init(arena);
                 for (diags.arch.?.allCpuModels()) |cpu| {
-                    help_text.writer().print(" {}\n", .{cpu.name}) catch break :help;
+                    help_text.writer().print(" {s}\n", .{cpu.name}) catch break :help;
                 }
-                std.log.info("Available CPUs for architecture '{}': {}", .{
+                std.log.info("Available CPUs for architecture '{s}': {s}", .{
                     @tagName(diags.arch.?), help_text.items,
                 });
             }
-            fatal("Unknown CPU: '{}'", .{diags.cpu_name.?});
+            fatal("Unknown CPU: '{s}'", .{diags.cpu_name.?});
         },
         error.UnknownCpuFeature => {
             help: {
                 var help_text = std.ArrayList(u8).init(arena);
                 for (diags.arch.?.allFeaturesList()) |feature| {
-                    help_text.writer().print(" {}: {}\n", .{ feature.name, feature.description }) catch break :help;
+                    help_text.writer().print(" {s}: {s}\n", .{ feature.name, feature.description }) catch break :help;
                 }
-                std.log.info("Available CPU features for architecture '{}': {}", .{
+                std.log.info("Available CPU features for architecture '{s}': {s}", .{
                     @tagName(diags.arch.?), help_text.items,
                 });
             }
-            fatal("Unknown CPU feature: '{}'", .{diags.unknown_feature_name});
+            fatal("Unknown CPU feature: '{s}'", .{diags.unknown_feature_name});
         },
         else => |e| return e,
     };
@@ -1431,10 +1431,10 @@ fn buildOutputType(
 
     if (cross_target.isNativeOs() and (system_libs.items.len != 0 or want_native_include_dirs)) {
         const paths = std.zig.system.NativePaths.detect(arena) catch |err| {
-            fatal("unable to detect native system paths: {}", .{@errorName(err)});
+            fatal("unable to detect native system paths: {s}", .{@errorName(err)});
         };
         for (paths.warnings.items) |warning| {
-            warn("{}", .{warning});
+            warn("{s}", .{warning});
         }
 
         const has_sysroot = if (comptime std.Target.current.isDarwin()) outer: {
@@ -1492,7 +1492,7 @@ fn buildOutputType(
         } else if (mem.eql(u8, ofmt, "raw")) {
             break :blk .raw;
         } else {
-            fatal("unsupported object format: {}", .{ofmt});
+            fatal("unsupported object format: {s}", .{ofmt});
         }
     };
 
@@ -1562,7 +1562,7 @@ fn buildOutputType(
             }
             if (fs.path.dirname(full_path)) |dirname| {
                 const handle = fs.cwd().openDir(dirname, .{}) catch |err| {
-                    fatal("unable to open output directory '{}': {}", .{ dirname, @errorName(err) });
+                    fatal("unable to open output directory '{s}': {s}", .{ dirname, @errorName(err) });
                 };
                 cleanup_emit_bin_dir = handle;
                 break :b Compilation.EmitLoc{
@@ -1585,19 +1585,19 @@ fn buildOutputType(
         },
     };
 
-    const default_h_basename = try std.fmt.allocPrint(arena, "{}.h", .{root_name});
+    const default_h_basename = try std.fmt.allocPrint(arena, "{s}.h", .{root_name});
     var emit_h_resolved = try emit_h.resolve(default_h_basename);
     defer emit_h_resolved.deinit();
 
-    const default_asm_basename = try std.fmt.allocPrint(arena, "{}.s", .{root_name});
+    const default_asm_basename = try std.fmt.allocPrint(arena, "{s}.s", .{root_name});
     var emit_asm_resolved = try emit_asm.resolve(default_asm_basename);
     defer emit_asm_resolved.deinit();
 
-    const default_llvm_ir_basename = try std.fmt.allocPrint(arena, "{}.ll", .{root_name});
+    const default_llvm_ir_basename = try std.fmt.allocPrint(arena, "{s}.ll", .{root_name});
     var emit_llvm_ir_resolved = try emit_llvm_ir.resolve(default_llvm_ir_basename);
     defer emit_llvm_ir_resolved.deinit();
 
-    const default_analysis_basename = try std.fmt.allocPrint(arena, "{}-analysis.json", .{root_name});
+    const default_analysis_basename = try std.fmt.allocPrint(arena, "{s}-analysis.json", .{root_name});
     var emit_analysis_resolved = try emit_analysis.resolve(default_analysis_basename);
     defer emit_analysis_resolved.deinit();
 
@@ -1609,10 +1609,10 @@ fn buildOutputType(
         .yes_default_path => blk: {
             if (root_src_file) |rsf| {
                 if (mem.endsWith(u8, rsf, ".zir")) {
-                    break :blk try std.fmt.allocPrint(arena, "{}.out.zir", .{root_name});
+                    break :blk try std.fmt.allocPrint(arena, "{s}.out.zir", .{root_name});
                 }
             }
-            break :blk try std.fmt.allocPrint(arena, "{}.zir", .{root_name});
+            break :blk try std.fmt.allocPrint(arena, "{s}.zir", .{root_name});
         },
         .yes => |p| p,
     };
@@ -1642,7 +1642,7 @@ fn buildOutputType(
         }
     else
         introspect.findZigLibDirFromSelfExe(arena, self_exe_path) catch |err| {
-            fatal("unable to find zig installation directory: {}", .{@errorName(err)});
+            fatal("unable to find zig installation directory: {s}", .{@errorName(err)});
         };
     defer zig_lib_directory.handle.close();
 
@@ -1655,7 +1655,7 @@ fn buildOutputType(
 
     if (libc_paths_file) |paths_file| {
         libc_installation = LibCInstallation.parse(gpa, paths_file) catch |err| {
-            fatal("unable to parse libc paths file: {}", .{@errorName(err)});
+            fatal("unable to parse libc paths file: {s}", .{@errorName(err)});
         };
     }
 
@@ -1791,7 +1791,7 @@ fn buildOutputType(
         .disable_lld_caching = !have_enable_cache,
         .subsystem = subsystem,
     }) catch |err| {
-        fatal("unable to create compilation: {}", .{@errorName(err)});
+        fatal("unable to create compilation: {s}", .{@errorName(err)});
     };
     var comp_destroyed = false;
     defer if (!comp_destroyed) comp.destroy();
@@ -1914,12 +1914,12 @@ fn buildOutputType(
                                 if (!watch) return cleanExit();
                             } else {
                                 const cmd = try argvCmd(arena, argv.items);
-                                fatal("the following test command failed with exit code {}:\n{}", .{ code, cmd });
+                                fatal("the following test command failed with exit code {}:\n{s}", .{ code, cmd });
                             }
                         },
                         else => {
                             const cmd = try argvCmd(arena, argv.items);
-                            fatal("the following test command crashed:\n{}", .{cmd});
+                            fatal("the following test command crashed:\n{s}", .{cmd});
                         },
                     }
                 },
@@ -1936,7 +1936,7 @@ fn buildOutputType(
         try stderr.print("(zig) ", .{});
         try comp.makeBinFileExecutable();
         if (stdin.readUntilDelimiterOrEof(&repl_buf, '\n') catch |err| {
-            try stderr.print("\nUnable to parse command: {}\n", .{@errorName(err)});
+            try stderr.print("\nUnable to parse command: {s}\n", .{@errorName(err)});
             continue;
         }) |line| {
             const actual_line = mem.trimRight(u8, line, "\r\n ");
@@ -1954,7 +1954,7 @@ fn buildOutputType(
             } else if (mem.eql(u8, actual_line, "help")) {
                 try stderr.writeAll(repl_help);
             } else {
-                try stderr.print("unknown command: {}\n", .{actual_line});
+                try stderr.print("unknown command: {s}\n", .{actual_line});
             }
         } else {
             break;
@@ -2012,14 +2012,14 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
     assert(comp.c_source_files.len == 1);
     const c_source_file = comp.c_source_files[0];
 
-    const translated_zig_basename = try std.fmt.allocPrint(arena, "{}.zig", .{comp.bin_file.options.root_name});
+    const translated_zig_basename = try std.fmt.allocPrint(arena, "{s}.zig", .{comp.bin_file.options.root_name});
 
     var man: Cache.Manifest = comp.obtainCObjectCacheManifest();
     defer if (enable_cache) man.deinit();
 
     man.hash.add(@as(u16, 0xb945)); // Random number to distinguish translate-c from compiling C objects
     _ = man.addFile(c_source_file.src_path, null) catch |err| {
-        fatal("unable to process '{}': {}", .{ c_source_file.src_path, @errorName(err) });
+        fatal("unable to process '{s}': {s}", .{ c_source_file.src_path, @errorName(err) });
     };
 
     const digest = if (try man.hit()) man.final() else digest: {
@@ -2034,7 +2034,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
                 break :blk null;
 
             const c_src_basename = fs.path.basename(c_source_file.src_path);
-            const dep_basename = try std.fmt.allocPrint(arena, "{}.d", .{c_src_basename});
+            const dep_basename = try std.fmt.allocPrint(arena, "{s}.d", .{c_src_basename});
             const out_dep_path = try comp.tmpFilePath(arena, dep_basename);
             break :blk out_dep_path;
         };
@@ -2069,7 +2069,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
             error.ASTUnitFailure => fatal("clang API returned errors but due to a clang bug, it is not exposing the errors for zig to see. For more details: https://github.com/ziglang/zig/issues/4455", .{}),
             error.SemanticAnalyzeFail => {
                 for (clang_errors) |clang_err| {
-                    std.debug.print("{}:{}:{}: {}\n", .{
+                    std.debug.print("{s}:{}:{}: {s}\n", .{
                         if (clang_err.filename_ptr) |p| p[0..clang_err.filename_len] else "(no file)",
                         clang_err.line + 1,
                         clang_err.column + 1,
@@ -2087,7 +2087,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
             try man.addDepFilePost(zig_cache_tmp_dir, dep_basename);
             // Just to save disk space, we delete the file because it is never needed again.
             zig_cache_tmp_dir.deleteFile(dep_basename) catch |err| {
-                warn("failed to delete '{}': {}", .{ dep_file_path, @errorName(err) });
+                warn("failed to delete '{s}': {s}", .{ dep_file_path, @errorName(err) });
             };
         }
 
@@ -2102,7 +2102,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
         _ = try std.zig.render(comp.gpa, bos.writer(), tree);
         try bos.flush();
 
-        man.writeManifest() catch |err| warn("failed to write cache manifest: {}", .{@errorName(err)});
+        man.writeManifest() catch |err| warn("failed to write cache manifest: {s}", .{@errorName(err)});
 
         break :digest digest;
     };
@@ -2111,7 +2111,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
         const full_zig_path = try comp.local_cache_directory.join(arena, &[_][]const u8{
             "o", &digest, translated_zig_basename,
         });
-        try io.getStdOut().writer().print("{}\n", .{full_zig_path});
+        try io.getStdOut().writer().print("{s}\n", .{full_zig_path});
         return cleanExit();
     } else {
         const out_zig_path = try fs.path.join(arena, &[_][]const u8{ "o", &digest, translated_zig_basename });
@@ -2148,10 +2148,10 @@ pub fn cmdLibC(gpa: *Allocator, args: []const []const u8) !void {
                     try stdout.writeAll(usage_libc);
                     return cleanExit();
                 } else {
-                    fatal("unrecognized parameter: '{}'", .{arg});
+                    fatal("unrecognized parameter: '{s}'", .{arg});
                 }
             } else if (input_file != null) {
-                fatal("unexpected extra parameter: '{}'", .{arg});
+                fatal("unexpected extra parameter: '{s}'", .{arg});
             } else {
                 input_file = arg;
             }
@@ -2159,7 +2159,7 @@ pub fn cmdLibC(gpa: *Allocator, args: []const []const u8) !void {
     }
     if (input_file) |libc_file| {
         var libc = LibCInstallation.parse(gpa, libc_file) catch |err| {
-            fatal("unable to parse libc file: {}", .{@errorName(err)});
+            fatal("unable to parse libc file: {s}", .{@errorName(err)});
         };
         defer libc.deinit(gpa);
     } else {
@@ -2167,7 +2167,7 @@ pub fn cmdLibC(gpa: *Allocator, args: []const []const u8) !void {
             .allocator = gpa,
             .verbose = true,
         }) catch |err| {
-            fatal("unable to detect native libc: {}", .{@errorName(err)});
+            fatal("unable to detect native libc: {s}", .{@errorName(err)});
         };
         defer libc.deinit(gpa);
 
@@ -2205,16 +2205,16 @@ pub fn cmdInit(
                     try io.getStdOut().writeAll(usage_init);
                     return cleanExit();
                 } else {
-                    fatal("unrecognized parameter: '{}'", .{arg});
+                    fatal("unrecognized parameter: '{s}'", .{arg});
                 }
             } else {
-                fatal("unexpected extra parameter: '{}'", .{arg});
+                fatal("unexpected extra parameter: '{s}'", .{arg});
             }
         }
     }
     const self_exe_path = try fs.selfExePathAlloc(arena);
     var zig_lib_directory = introspect.findZigLibDirFromSelfExe(arena, self_exe_path) catch |err| {
-        fatal("unable to find zig installation directory: {}\n", .{@errorName(err)});
+        fatal("unable to find zig installation directory: {s}\n", .{@errorName(err)});
     };
     defer zig_lib_directory.handle.close();
 
@@ -2232,7 +2232,7 @@ pub fn cmdInit(
 
     const max_bytes = 10 * 1024 * 1024;
     const build_zig_contents = template_dir.readFileAlloc(arena, "build.zig", max_bytes) catch |err| {
-        fatal("unable to read template file 'build.zig': {}", .{@errorName(err)});
+        fatal("unable to read template file 'build.zig': {s}", .{@errorName(err)});
     };
     var modified_build_zig_contents = std.ArrayList(u8).init(arena);
     try modified_build_zig_contents.ensureCapacity(build_zig_contents.len);
@@ -2244,13 +2244,13 @@ pub fn cmdInit(
         }
     }
     const main_zig_contents = template_dir.readFileAlloc(arena, "src" ++ s ++ "main.zig", max_bytes) catch |err| {
-        fatal("unable to read template file 'main.zig': {}", .{@errorName(err)});
+        fatal("unable to read template file 'main.zig': {s}", .{@errorName(err)});
     };
     if (fs.cwd().access("build.zig", .{})) |_| {
         fatal("existing build.zig file would be overwritten", .{});
     } else |err| switch (err) {
         error.FileNotFound => {},
-        else => fatal("unable to test existence of build.zig: {}\n", .{@errorName(err)}),
+        else => fatal("unable to test existence of build.zig: {s}\n", .{@errorName(err)}),
     }
     var src_dir = try fs.cwd().makeOpenPath("src", .{});
     defer src_dir.close();
@@ -2311,23 +2311,23 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
                 const arg = args[i];
                 if (mem.startsWith(u8, arg, "-")) {
                     if (mem.eql(u8, arg, "--build-file")) {
-                        if (i + 1 >= args.len) fatal("expected argument after '{}'", .{arg});
+                        if (i + 1 >= args.len) fatal("expected argument after '{s}'", .{arg});
                         i += 1;
                         build_file = args[i];
                         continue;
                     } else if (mem.eql(u8, arg, "--override-lib-dir")) {
-                        if (i + 1 >= args.len) fatal("expected argument after '{}'", .{arg});
+                        if (i + 1 >= args.len) fatal("expected argument after '{s}'", .{arg});
                         i += 1;
                         override_lib_dir = args[i];
                         try child_argv.appendSlice(&[_][]const u8{ arg, args[i] });
                         continue;
                     } else if (mem.eql(u8, arg, "--cache-dir")) {
-                        if (i + 1 >= args.len) fatal("expected argument after '{}'", .{arg});
+                        if (i + 1 >= args.len) fatal("expected argument after '{s}'", .{arg});
                         i += 1;
                         override_local_cache_dir = args[i];
                         continue;
                     } else if (mem.eql(u8, arg, "--global-cache-dir")) {
-                        if (i + 1 >= args.len) fatal("expected argument after '{}'", .{arg});
+                        if (i + 1 >= args.len) fatal("expected argument after '{s}'", .{arg});
                         i += 1;
                         override_global_cache_dir = args[i];
                         continue;
@@ -2344,7 +2344,7 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
             }
         else
             introspect.findZigLibDirFromSelfExe(arena, self_exe_path) catch |err| {
-                fatal("unable to find zig installation directory: {}", .{@errorName(err)});
+                fatal("unable to find zig installation directory: {s}", .{@errorName(err)});
             };
         defer zig_lib_directory.handle.close();
 
@@ -2385,7 +2385,7 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
                 } else |err| switch (err) {
                     error.FileNotFound => {
                         dirname = fs.path.dirname(dirname) orelse {
-                            std.log.info("{}", .{
+                            std.log.info("{s}", .{
                                 \\Initialize a 'build.zig' template file with `zig init-lib` or `zig init-exe`,
                                 \\or see `zig --help` for more options.
                             });
@@ -2467,7 +2467,7 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
             .self_exe_path = self_exe_path,
             .thread_pool = &thread_pool,
         }) catch |err| {
-            fatal("unable to create compilation: {}", .{@errorName(err)});
+            fatal("unable to create compilation: {s}", .{@errorName(err)});
         };
         defer comp.destroy();
 
@@ -2493,11 +2493,11 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
         .Exited => |code| {
             if (code == 0) return cleanExit();
             const cmd = try argvCmd(arena, child_argv);
-            fatal("the following build command failed with exit code {}:\n{}", .{ code, cmd });
+            fatal("the following build command failed with exit code {}:\n{s}", .{ code, cmd });
         },
         else => {
             const cmd = try argvCmd(arena, child_argv);
-            fatal("the following build command crashed:\n{}", .{cmd});
+            fatal("the following build command crashed:\n{s}", .{cmd});
         },
     }
 }
@@ -2564,14 +2564,14 @@ pub fn cmdFmt(gpa: *Allocator, args: []const []const u8) !void {
                     i += 1;
                     const next_arg = args[i];
                     color = std.meta.stringToEnum(Color, next_arg) orelse {
-                        fatal("expected [auto|on|off] after --color, found '{}'", .{next_arg});
+                        fatal("expected [auto|on|off] after --color, found '{s}'", .{next_arg});
                     };
                 } else if (mem.eql(u8, arg, "--stdin")) {
                     stdin_flag = true;
                 } else if (mem.eql(u8, arg, "--check")) {
                     check_flag = true;
                 } else {
-                    fatal("unrecognized parameter: '{}'", .{arg});
+                    fatal("unrecognized parameter: '{s}'", .{arg});
                 }
             } else {
                 try input_files.append(arg);
@@ -2590,7 +2590,7 @@ pub fn cmdFmt(gpa: *Allocator, args: []const []const u8) !void {
         defer gpa.free(source_code);
 
         const tree = std.zig.parse(gpa, source_code) catch |err| {
-            fatal("error parsing stdin: {}", .{err});
+            fatal("error parsing stdin: {s}", .{err});
         };
         defer tree.deinit();
 
@@ -2629,7 +2629,7 @@ pub fn cmdFmt(gpa: *Allocator, args: []const []const u8) !void {
     for (input_files.items) |file_path| {
         // Get the real path here to avoid Windows failing on relative file paths with . or .. in them.
         const real_path = fs.realpathAlloc(gpa, file_path) catch |err| {
-            fatal("unable to open '{}': {}", .{ file_path, err });
+            fatal("unable to open '{s}': {s}", .{ file_path, @errorName(err) });
         };
         defer gpa.free(real_path);
 
@@ -2668,7 +2668,7 @@ fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool, dir: fs.Dir, sub_
     fmtPathFile(fmt, file_path, check_mode, dir, sub_path) catch |err| switch (err) {
         error.IsDir, error.AccessDenied => return fmtPathDir(fmt, file_path, check_mode, dir, sub_path),
         else => {
-            warn("unable to format '{}': {}", .{ file_path, err });
+            warn("unable to format '{s}': {s}", .{ file_path, @errorName(err) });
             fmt.any_error = true;
             return;
         },
@@ -2702,7 +2702,7 @@ fn fmtPathDir(
                 try fmtPathDir(fmt, full_path, check_mode, dir, entry.name);
             } else {
                 fmtPathFile(fmt, full_path, check_mode, dir, entry.name) catch |err| {
-                    warn("unable to format '{}': {}", .{ full_path, err });
+                    warn("unable to format '{s}': {s}", .{ full_path, @errorName(err) });
                     fmt.any_error = true;
                     return;
                 };
@@ -2761,7 +2761,7 @@ fn fmtPathFile(
         const anything_changed = try std.zig.render(fmt.gpa, io.null_out_stream, tree);
         if (anything_changed) {
             const stdout = io.getStdOut().writer();
-            try stdout.print("{}\n", .{file_path});
+            try stdout.print("{s}\n", .{file_path});
             fmt.any_error = true;
         }
     } else {
@@ -2779,7 +2779,7 @@ fn fmtPathFile(
         try af.file.writeAll(fmt.out_buffer.items);
         try af.finish();
         const stdout = io.getStdOut().writer();
-        try stdout.print("{}\n", .{file_path});
+        try stdout.print("{s}\n", .{file_path});
     }
 }
 
@@ -2812,7 +2812,7 @@ fn printErrMsgToFile(
     const text = text_buf.items;
 
     const stream = file.outStream();
-    try stream.print("{}:{}:{}: error: {}\n", .{ path, start_loc.line + 1, start_loc.column + 1, text });
+    try stream.print("{s}:{}:{}: error: {s}\n", .{ path, start_loc.line + 1, start_loc.column + 1, text });
 
     if (!color_on) return;
 
@@ -2984,7 +2984,7 @@ pub const ClangArgIterator = struct {
             const max_bytes = 10 * 1024 * 1024; // 10 MiB of command line arguments is a reasonable limit
             const resp_file_path = arg[1..];
             const resp_contents = fs.cwd().readFileAlloc(allocator, resp_file_path, max_bytes) catch |err| {
-                fatal("unable to read response file '{}': {}", .{ resp_file_path, @errorName(err) });
+                fatal("unable to read response file '{s}': {s}", .{ resp_file_path, @errorName(err) });
             };
             defer allocator.free(resp_contents);
             // TODO is there a specification for this file format? Let's find it and make this parsing more robust
@@ -3057,7 +3057,7 @@ pub const ClangArgIterator = struct {
                 const prefix_len = clang_arg.matchStartsWith(arg);
                 if (prefix_len == arg.len) {
                     if (self.next_index >= self.argv.len) {
-                        fatal("Expected parameter after '{}'", .{arg});
+                        fatal("Expected parameter after '{s}'", .{arg});
                     }
                     self.only_arg = self.argv[self.next_index];
                     self.incrementArgIndex();
@@ -3078,7 +3078,7 @@ pub const ClangArgIterator = struct {
                 if (prefix_len != 0) {
                     self.only_arg = arg[prefix_len..];
                     if (self.next_index >= self.argv.len) {
-                        fatal("Expected parameter after '{}'", .{arg});
+                        fatal("Expected parameter after '{s}'", .{arg});
                     }
                     self.second_arg = self.argv[self.next_index];
                     self.incrementArgIndex();
@@ -3089,7 +3089,7 @@ pub const ClangArgIterator = struct {
             },
             .separate => if (clang_arg.matchEql(arg) > 0) {
                 if (self.next_index >= self.argv.len) {
-                    fatal("Expected parameter after '{}'", .{arg});
+                    fatal("Expected parameter after '{s}'", .{arg});
                 }
                 self.only_arg = self.argv[self.next_index];
                 self.incrementArgIndex();
@@ -3115,7 +3115,7 @@ pub const ClangArgIterator = struct {
             },
         }
         else {
-            fatal("Unknown Clang option: '{}'", .{arg});
+            fatal("Unknown Clang option: '{s}'", .{arg});
         }
     }
 
@@ -3143,7 +3143,7 @@ pub const ClangArgIterator = struct {
 
 fn parseCodeModel(arg: []const u8) std.builtin.CodeModel {
     return std.meta.stringToEnum(std.builtin.CodeModel, arg) orelse
-        fatal("unsupported machine code model: '{}'", .{arg});
+        fatal("unsupported machine code model: '{s}'", .{arg});
 }
 
 /// Raise the open file descriptor limit. Ask and ye shall receive.
@@ -3263,7 +3263,7 @@ fn detectNativeTargetInfo(gpa: *Allocator, cross_target: std.zig.CrossTarget) !s
         // CPU model & feature detection is todo so here we rely on LLVM.
         // https://github.com/ziglang/zig/issues/4591
         if (!build_options.have_llvm)
-            fatal("CPU features detection is not yet available for {} without LLVM extensions", .{@tagName(arch)});
+            fatal("CPU features detection is not yet available for {s} without LLVM extensions", .{@tagName(arch)});
 
         const llvm = @import("llvm_bindings.zig");
         const llvm_cpu_name = llvm.GetHostCPUName();
diff --git a/src/mingw.zig b/src/mingw.zig
index 246b0f33dc..d55cc28b2b 100644
--- a/src/mingw.zig
+++ b/src/mingw.zig
@@ -381,7 +381,7 @@ pub fn buildImportLib(comp: *Compilation, lib_name: []const u8) !void {
 
     const term = child.wait() catch |err| {
         // TODO surface a proper error here
-        log.err("unable to spawn {}: {}", .{ args[0], @errorName(err) });
+        log.err("unable to spawn {s}: {s}", .{ args[0], @errorName(err) });
         return error.ClangPreprocessorFailed;
     };
 
@@ -395,7 +395,7 @@ pub fn buildImportLib(comp: *Compilation, lib_name: []const u8) !void {
         },
         else => {
             // TODO surface a proper error here
-            log.err("clang terminated unexpectedly with stderr: {}", .{stderr});
+            log.err("clang terminated unexpectedly with stderr: {s}", .{stderr});
             return error.ClangPreprocessorFailed;
         },
     }
diff --git a/src/musl.zig b/src/musl.zig
index f67fe90add..a865e78623 100644
--- a/src/musl.zig
+++ b/src/musl.zig
@@ -155,21 +155,21 @@ pub fn buildCRTFile(comp: *Compilation, crt_file: CRTFile) !void {
                 if (!is_arch_specific) {
                     // Look for an arch specific override.
                     override_path.shrinkRetainingCapacity(0);
-                    try override_path.writer().print("{}" ++ s ++ "{}" ++ s ++ "{}.s", .{
+                    try override_path.writer().print("{s}" ++ s ++ "{s}" ++ s ++ "{s}.s", .{
                         dirname, arch_name, noextbasename,
                     });
                     if (source_table.contains(override_path.items))
                         continue;
 
                     override_path.shrinkRetainingCapacity(0);
-                    try override_path.writer().print("{}" ++ s ++ "{}" ++ s ++ "{}.S", .{
+                    try override_path.writer().print("{s}" ++ s ++ "{s}" ++ s ++ "{s}.S", .{
                         dirname, arch_name, noextbasename,
                     });
                     if (source_table.contains(override_path.items))
                         continue;
 
                     override_path.shrinkRetainingCapacity(0);
-                    try override_path.writer().print("{}" ++ s ++ "{}" ++ s ++ "{}.c", .{
+                    try override_path.writer().print("{s}" ++ s ++ "{s}" ++ s ++ "{s}.c", .{
                         dirname, arch_name, noextbasename,
                     });
                     if (source_table.contains(override_path.items))
@@ -322,7 +322,7 @@ fn add_cc_args(
     const target = comp.getTarget();
     const arch_name = target_util.archMuslName(target.cpu.arch);
     const os_name = @tagName(target.os.tag);
-    const triple = try std.fmt.allocPrint(arena, "{}-{}-musl", .{ arch_name, os_name });
+    const triple = try std.fmt.allocPrint(arena, "{s}-{s}-musl", .{ arch_name, os_name });
     const o_arg = if (want_O3) "-O3" else "-Os";
 
     try args.appendSlice(&[_][]const u8{
diff --git a/src/print_env.zig b/src/print_env.zig
index 8aa692e644..bcf4a983ab 100644
--- a/src/print_env.zig
+++ b/src/print_env.zig
@@ -9,7 +9,7 @@ pub fn cmdEnv(gpa: *Allocator, args: []const []const u8, stdout: std.fs.File.Wri
     defer gpa.free(self_exe_path);
 
     var zig_lib_directory = introspect.findZigLibDirFromSelfExe(gpa, self_exe_path) catch |err| {
-        fatal("unable to find zig installation directory: {}\n", .{@errorName(err)});
+        fatal("unable to find zig installation directory: {s}\n", .{@errorName(err)});
     };
     defer gpa.free(zig_lib_directory.path.?);
     defer zig_lib_directory.handle.close();
diff --git a/src/print_targets.zig b/src/print_targets.zig
index 724cb7a9ac..cf55eee516 100644
--- a/src/print_targets.zig
+++ b/src/print_targets.zig
@@ -18,7 +18,7 @@ pub fn cmdTargets(
     native_target: Target,
 ) !void {
     var zig_lib_directory = introspect.findZigLibDir(allocator) catch |err| {
-        fatal("unable to find zig installation directory: {}\n", .{@errorName(err)});
+        fatal("unable to find zig installation directory: {s}\n", .{@errorName(err)});
     };
     defer zig_lib_directory.handle.close();
     defer allocator.free(zig_lib_directory.path.?);
@@ -61,7 +61,7 @@ pub fn cmdTargets(
     try jws.objectField("libc");
     try jws.beginArray();
     for (target.available_libcs) |libc| {
-        const tmp = try std.fmt.allocPrint(allocator, "{}-{}-{}", .{
+        const tmp = try std.fmt.allocPrint(allocator, "{s}-{s}-{s}", .{
             @tagName(libc.arch), @tagName(libc.os), @tagName(libc.abi),
         });
         defer allocator.free(tmp);
diff --git a/src/stage1.zig b/src/stage1.zig
index 1d50a71ad1..cf3a252ce8 100644
--- a/src/stage1.zig
+++ b/src/stage1.zig
@@ -37,14 +37,14 @@ pub export fn main(argc: c_int, argv: [*][*:0]u8) c_int {
     defer arena_instance.deinit();
     const arena = &arena_instance.allocator;
 
-    const args = arena.alloc([]const u8, @intCast(usize, argc)) catch fatal("{}", .{"OutOfMemory"});
+    const args = arena.alloc([]const u8, @intCast(usize, argc)) catch fatal("{s}", .{"OutOfMemory"});
     for (args) |*arg, i| {
         arg.* = mem.spanZ(argv[i]);
     }
     if (std.builtin.mode == .Debug) {
         stage2.mainArgs(gpa, arena, args) catch unreachable;
     } else {
-        stage2.mainArgs(gpa, arena, args) catch |err| fatal("{}", .{@errorName(err)});
+        stage2.mainArgs(gpa, arena, args) catch |err| fatal("{s}", .{@errorName(err)});
     }
     return 0;
 }
diff --git a/src/translate_c.zig b/src/translate_c.zig
index 1b2aa4b219..c609597770 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -136,7 +136,7 @@ const Scope = struct {
             var proposed_name = name_copy;
             while (scope.contains(proposed_name)) {
                 scope.mangle_count += 1;
-                proposed_name = try std.fmt.allocPrint(c.arena, "{}_{}", .{ name, scope.mangle_count });
+                proposed_name = try std.fmt.allocPrint(c.arena, "{s}_{}", .{ name, scope.mangle_count });
             }
             try scope.variables.append(.{ .name = name_copy, .alias = proposed_name });
             return proposed_name;
@@ -290,7 +290,7 @@ pub const Context = struct {
 
         const line = c.source_manager.getSpellingLineNumber(spelling_loc);
         const column = c.source_manager.getSpellingColumnNumber(spelling_loc);
-        return std.fmt.allocPrint(c.arena, "{}:{}:{}", .{ filename, line, column });
+        return std.fmt.allocPrint(c.arena, "{s}:{d}:{d}", .{ filename, line, column });
     }
 
     fn createCall(c: *Context, fn_expr: *ast.Node, params_len: ast.NodeIndex) !*ast.Node.Call {
@@ -530,7 +530,7 @@ fn declVisitor(c: *Context, decl: *const clang.Decl) Error!void {
         },
         else => {
             const decl_name = try c.str(decl.getDeclKindName());
-            try emitWarning(c, decl.getLocation(), "ignoring {} declaration", .{decl_name});
+            try emitWarning(c, decl.getLocation(), "ignoring {s} declaration", .{decl_name});
         },
     }
 }
@@ -625,7 +625,7 @@ fn visitFnDecl(c: *Context, fn_decl: *const clang.FunctionDecl) Error!void {
         const param_name = if (param.name_token) |name_tok|
             tokenSlice(c, name_tok)
         else
-            return failDecl(c, fn_decl_loc, fn_name, "function {} parameter has no name", .{fn_name});
+            return failDecl(c, fn_decl_loc, fn_name, "function {s} parameter has no name", .{fn_name});
 
         const c_param = fn_decl.getParamDecl(param_id);
         const qual_type = c_param.getOriginalType();
@@ -634,7 +634,7 @@ fn visitFnDecl(c: *Context, fn_decl: *const clang.FunctionDecl) Error!void {
         const mangled_param_name = try block_scope.makeMangledName(c, param_name);
 
         if (!is_const) {
-            const bare_arg_name = try std.fmt.allocPrint(c.arena, "arg_{}", .{mangled_param_name});
+            const bare_arg_name = try std.fmt.allocPrint(c.arena, "arg_{s}", .{mangled_param_name});
             const arg_name = try block_scope.makeMangledName(c, bare_arg_name);
 
             const mut_tok = try appendToken(c, .Keyword_var, "var");
@@ -727,7 +727,7 @@ fn visitVarDecl(c: *Context, var_decl: *const clang.VarDecl, mangled_name: ?[]co
 
     // TODO https://github.com/ziglang/zig/issues/3756
     // TODO https://github.com/ziglang/zig/issues/1802
-    const checked_name = if (isZigPrimitiveType(var_name)) try std.fmt.allocPrint(c.arena, "{}_{}", .{ var_name, c.getMangle() }) else var_name;
+    const checked_name = if (isZigPrimitiveType(var_name)) try std.fmt.allocPrint(c.arena, "{s}_{d}", .{ var_name, c.getMangle() }) else var_name;
     const var_decl_loc = var_decl.getLocation();
 
     const qual_type = var_decl.getTypeSourceInfo_getType();
@@ -808,7 +808,7 @@ fn visitVarDecl(c: *Context, var_decl: *const clang.VarDecl, mangled_name: ?[]co
             _ = try appendToken(rp.c, .LParen, "(");
             const expr = try transCreateNodeStringLiteral(
                 rp.c,
-                try std.fmt.allocPrint(rp.c.arena, "\"{}\"", .{str_ptr[0..str_len]}),
+                try std.fmt.allocPrint(rp.c.arena, "\"{s}\"", .{str_ptr[0..str_len]}),
             );
             _ = try appendToken(rp.c, .RParen, ")");
 
@@ -887,7 +887,7 @@ fn transTypeDef(c: *Context, typedef_decl: *const clang.TypedefNameDecl, top_lev
 
     // TODO https://github.com/ziglang/zig/issues/3756
     // TODO https://github.com/ziglang/zig/issues/1802
-    const checked_name = if (isZigPrimitiveType(typedef_name)) try std.fmt.allocPrint(c.arena, "{}_{}", .{ typedef_name, c.getMangle() }) else typedef_name;
+    const checked_name = if (isZigPrimitiveType(typedef_name)) try std.fmt.allocPrint(c.arena, "{s}_{d}", .{ typedef_name, c.getMangle() }) else typedef_name;
     if (checkForBuiltinTypedef(checked_name)) |builtin| {
         return transTypeDefAsBuiltin(c, typedef_decl, builtin);
     }
@@ -958,11 +958,11 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
         container_kind_name = "struct";
         container_kind = .Keyword_struct;
     } else {
-        try emitWarning(c, record_loc, "record {} is not a struct or union", .{bare_name});
+        try emitWarning(c, record_loc, "record {s} is not a struct or union", .{bare_name});
         return null;
     }
 
-    const name = try std.fmt.allocPrint(c.arena, "{}_{}", .{ container_kind_name, bare_name });
+    const name = try std.fmt.allocPrint(c.arena, "{s}_{s}", .{ container_kind_name, bare_name });
     _ = try c.decl_table.put(c.gpa, @ptrToInt(record_decl.getCanonicalDecl()), name);
 
     const visib_tok = if (!is_unnamed) try appendToken(c, .Keyword_pub, "pub") else null;
@@ -1003,7 +1003,7 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
                 _ = try c.opaque_demotes.put(c.gpa, @ptrToInt(record_decl.getCanonicalDecl()), {});
                 const opaque_type = try transCreateNodeOpaqueType(c);
                 semicolon = try appendToken(c, .Semicolon, ";");
-                try emitWarning(c, field_loc, "{} demoted to opaque type - has bitfield", .{container_kind_name});
+                try emitWarning(c, field_loc, "{s} demoted to opaque type - has bitfield", .{container_kind_name});
                 break :blk opaque_type;
             }
 
@@ -1011,7 +1011,7 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
                 _ = try c.opaque_demotes.put(c.gpa, @ptrToInt(record_decl.getCanonicalDecl()), {});
                 const opaque_type = try transCreateNodeOpaqueType(c);
                 semicolon = try appendToken(c, .Semicolon, ";");
-                try emitWarning(c, field_loc, "{} demoted to opaque type - has variable length array", .{container_kind_name});
+                try emitWarning(c, field_loc, "{s} demoted to opaque type - has variable length array", .{container_kind_name});
                 break :blk opaque_type;
             }
 
@@ -1030,7 +1030,7 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
                     _ = try c.opaque_demotes.put(c.gpa, @ptrToInt(record_decl.getCanonicalDecl()), {});
                     const opaque_type = try transCreateNodeOpaqueType(c);
                     semicolon = try appendToken(c, .Semicolon, ";");
-                    try emitWarning(c, record_loc, "{} demoted to opaque type - unable to translate type of field {}", .{ container_kind_name, raw_name });
+                    try emitWarning(c, record_loc, "{s} demoted to opaque type - unable to translate type of field {s}", .{ container_kind_name, raw_name });
                     break :blk opaque_type;
                 },
                 else => |e| return e,
@@ -1114,7 +1114,7 @@ fn transEnumDecl(c: *Context, enum_decl: *const clang.EnumDecl) Error!?*ast.Node
         is_unnamed = true;
     }
 
-    const name = try std.fmt.allocPrint(c.arena, "enum_{}", .{bare_name});
+    const name = try std.fmt.allocPrint(c.arena, "enum_{s}", .{bare_name});
     _ = try c.decl_table.put(c.gpa, @ptrToInt(enum_decl.getCanonicalDecl()), name);
 
     const visib_tok = if (!is_unnamed) try appendToken(c, .Keyword_pub, "pub") else null;
@@ -1385,7 +1385,7 @@ fn transStmt(
                 rp,
                 error.UnsupportedTranslation,
                 stmt.getBeginLoc(),
-                "TODO implement translation of stmt class {}",
+                "TODO implement translation of stmt class {s}",
                 .{@tagName(sc)},
             );
         },
@@ -1684,7 +1684,7 @@ fn transDeclStmtOne(
             rp,
             error.UnsupportedTranslation,
             decl.getLocation(),
-            "TODO implement translation of DeclStmt kind {}",
+            "TODO implement translation of DeclStmt kind {s}",
             .{@tagName(kind)},
         ),
     }
@@ -1782,7 +1782,7 @@ fn transImplicitCastExpr(
             rp,
             error.UnsupportedTranslation,
             @ptrCast(*const clang.Stmt, expr).getBeginLoc(),
-            "TODO implement translation of CastKind {}",
+            "TODO implement translation of CastKind {s}",
             .{@tagName(kind)},
         ),
     }
@@ -2043,7 +2043,7 @@ fn transStringLiteral(
             rp,
             error.UnsupportedTranslation,
             @ptrCast(*const clang.Stmt, stmt).getBeginLoc(),
-            "TODO: support string literal kind {}",
+            "TODO: support string literal kind {s}",
             .{kind},
         ),
     }
@@ -2168,7 +2168,6 @@ fn transCCast(
         // @boolToInt returns either a comptime_int or a u1
         // TODO: if dst_type is 1 bit & signed (bitfield) we need @bitCast
         // instead of @as
-
         const builtin_node = try rp.c.createBuiltinCall("@boolToInt", 1);
         builtin_node.params()[0] = expr;
         builtin_node.rparen_token = try appendToken(rp.c, .RParen, ")");
@@ -2455,7 +2454,7 @@ fn transInitListExpr(
         );
     } else {
         const type_name = rp.c.str(qual_type.getTypeClassName());
-        return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported initlist type: '{}'", .{type_name});
+        return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported initlist type: '{s}'", .{type_name});
     }
 }
 
@@ -4433,7 +4432,8 @@ fn transCreateNodeBoolLiteral(c: *Context, value: bool) !*ast.Node {
 }
 
 fn transCreateNodeInt(c: *Context, int: anytype) !*ast.Node {
-    const token = try appendTokenFmt(c, .IntegerLiteral, "{}", .{int});
+    const fmt_s = if (comptime std.meta.trait.isIntegerNumber(@TypeOf(int))) "{d}" else "{s}";
+    const token = try appendTokenFmt(c, .IntegerLiteral, fmt_s, .{int});
     const node = try c.arena.create(ast.Node.OneToken);
     node.* = .{
         .base = .{ .tag = .IntegerLiteral },
@@ -4442,8 +4442,8 @@ fn transCreateNodeInt(c: *Context, int: anytype) !*ast.Node {
     return &node.base;
 }
 
-fn transCreateNodeFloat(c: *Context, int: anytype) !*ast.Node {
-    const token = try appendTokenFmt(c, .FloatLiteral, "{}", .{int});
+fn transCreateNodeFloat(c: *Context, str: []const u8) !*ast.Node {
+    const token = try appendTokenFmt(c, .FloatLiteral, "{s}", .{str});
     const node = try c.arena.create(ast.Node.OneToken);
     node.* = .{
         .base = .{ .tag = .FloatLiteral },
@@ -4916,7 +4916,7 @@ fn transType(rp: RestorePoint, ty: *const clang.Type, source_loc: clang.SourceLo
         },
         else => {
             const type_name = rp.c.str(ty.getTypeClassName());
-            return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported type: '{}'", .{type_name});
+            return revertAndWarn(rp, error.UnsupportedType, source_loc, "unsupported type: '{s}'", .{type_name});
         },
     }
 }
@@ -4999,7 +4999,7 @@ fn transCC(
             rp,
             error.UnsupportedType,
             source_loc,
-            "unsupported calling convention: {}",
+            "unsupported calling convention: {s}",
             .{@tagName(clang_cc)},
         ),
     }
@@ -5117,7 +5117,7 @@ fn finishTransFnProto(
                 _ = try appendToken(rp.c, .LParen, "(");
                 const expr = try transCreateNodeStringLiteral(
                     rp.c,
-                    try std.fmt.allocPrint(rp.c.arena, "\"{}\"", .{str_ptr[0..str_len]}),
+                    try std.fmt.allocPrint(rp.c.arena, "\"{s}\"", .{str_ptr[0..str_len]}),
                 );
                 _ = try appendToken(rp.c, .RParen, ")");
 
@@ -5214,7 +5214,7 @@ fn revertAndWarn(
 
 fn emitWarning(c: *Context, loc: clang.SourceLocation, comptime format: []const u8, args: anytype) !void {
     const args_prefix = .{c.locStr(loc)};
-    _ = try appendTokenFmt(c, .LineComment, "// {}: warning: " ++ format, args_prefix ++ args);
+    _ = try appendTokenFmt(c, .LineComment, "// {s}: warning: " ++ format, args_prefix ++ args);
 }
 
 pub fn failDecl(c: *Context, loc: clang.SourceLocation, name: []const u8, comptime format: []const u8, args: anytype) !void {
@@ -5228,7 +5228,7 @@ pub fn failDecl(c: *Context, loc: clang.SourceLocation, name: []const u8, compti
     const msg_tok = try appendTokenFmt(c, .StringLiteral, "\"" ++ format ++ "\"", args);
     const rparen_tok = try appendToken(c, .RParen, ")");
     const semi_tok = try appendToken(c, .Semicolon, ";");
-    _ = try appendTokenFmt(c, .LineComment, "// {}", .{c.locStr(loc)});
+    _ = try appendTokenFmt(c, .LineComment, "// {s}", .{c.locStr(loc)});
 
     const msg_node = try c.arena.create(ast.Node.OneToken);
     msg_node.* = .{
@@ -5258,7 +5258,7 @@ pub fn failDecl(c: *Context, loc: clang.SourceLocation, name: []const u8, compti
 
 fn appendToken(c: *Context, token_id: Token.Id, bytes: []const u8) !ast.TokenIndex {
     std.debug.assert(token_id != .Identifier); // use appendIdentifier
-    return appendTokenFmt(c, token_id, "{}", .{bytes});
+    return appendTokenFmt(c, token_id, "{s}", .{bytes});
 }
 
 fn appendTokenFmt(c: *Context, token_id: Token.Id, comptime format: []const u8, args: anytype) !ast.TokenIndex {
@@ -5329,7 +5329,7 @@ fn transCreateNodeIdentifier(c: *Context, name: []const u8) !*ast.Node {
 }
 
 fn transCreateNodeIdentifierUnchecked(c: *Context, name: []const u8) !*ast.Node {
-    const token_index = try appendTokenFmt(c, .Identifier, "{}", .{name});
+    const token_index = try appendTokenFmt(c, .Identifier, "{s}", .{name});
     const identifier = try c.arena.create(ast.Node.OneToken);
     identifier.* = .{
         .base = .{ .tag = .Identifier },
@@ -5390,7 +5390,7 @@ fn transPreprocessorEntities(c: *Context, unit: *clang.ASTUnit) Error!void {
                 const name = try c.str(raw_name);
                 // TODO https://github.com/ziglang/zig/issues/3756
                 // TODO https://github.com/ziglang/zig/issues/1802
-                const mangled_name = if (isZigPrimitiveType(name)) try std.fmt.allocPrint(c.arena, "{}_{}", .{ name, c.getMangle() }) else name;
+                const mangled_name = if (isZigPrimitiveType(name)) try std.fmt.allocPrint(c.arena, "{s}_{d}", .{ name, c.getMangle() }) else name;
                 if (scope.containsNow(mangled_name)) {
                     continue;
                 }
@@ -5468,7 +5468,7 @@ fn transMacroDefine(c: *Context, m: *MacroCtx) ParseError!void {
     const init_node = try parseCExpr(c, m, scope);
     const last = m.next().?;
     if (last != .Eof and last != .Nl)
-        return m.fail(c, "unable to translate C expr: unexpected token .{}", .{@tagName(last)});
+        return m.fail(c, "unable to translate C expr: unexpected token .{s}", .{@tagName(last)});
 
     const semicolon_token = try appendToken(c, .Semicolon, ";");
     const node = try ast.Node.VarDecl.create(c.arena, .{
@@ -5540,7 +5540,7 @@ fn transMacroFnDefine(c: *Context, m: *MacroCtx) ParseError!void {
     const expr = try parseCExpr(c, m, scope);
     const last = m.next().?;
     if (last != .Eof and last != .Nl)
-        return m.fail(c, "unable to translate C expr: unexpected token .{}", .{@tagName(last)});
+        return m.fail(c, "unable to translate C expr: unexpected token .{s}", .{@tagName(last)});
     _ = try appendToken(c, .Semicolon, ";");
     const type_of_arg = if (!expr.tag.isBlock()) expr else blk: {
         const stmts = expr.blockStatements();
@@ -5623,11 +5623,11 @@ fn parseCNumLit(c: *Context, m: *MacroCtx) ParseError!*ast.Node {
                 switch (lit_bytes[1]) {
                     '0'...'7' => {
                         // Octal
-                        lit_bytes = try std.fmt.allocPrint(c.arena, "0o{}", .{lit_bytes});
+                        lit_bytes = try std.fmt.allocPrint(c.arena, "0o{s}", .{lit_bytes});
                     },
                     'X' => {
                         // Hexadecimal with capital X, valid in C but not in Zig
-                        lit_bytes = try std.fmt.allocPrint(c.arena, "0x{}", .{lit_bytes[2..]});
+                        lit_bytes = try std.fmt.allocPrint(c.arena, "0x{s}", .{lit_bytes[2..]});
                     },
                     else => {},
                 }
@@ -5659,7 +5659,7 @@ fn parseCNumLit(c: *Context, m: *MacroCtx) ParseError!*ast.Node {
         },
         .FloatLiteral => |suffix| {
             if (lit_bytes[0] == '.')
-                lit_bytes = try std.fmt.allocPrint(c.arena, "0{}", .{lit_bytes});
+                lit_bytes = try std.fmt.allocPrint(c.arena, "0{s}", .{lit_bytes});
             if (suffix == .none) {
                 return transCreateNodeFloat(c, lit_bytes);
             }
@@ -5937,7 +5937,7 @@ fn parseCPrimaryExprInner(c: *Context, m: *MacroCtx, scope: *Scope) ParseError!*
 
             const next_id = m.next().?;
             if (next_id != .RParen) {
-                try m.fail(c, "unable to translate C expr: expected ')' instead got: {}", .{@tagName(next_id)});
+                try m.fail(c, "unable to translate C expr: expected ')' instead got: {s}", .{@tagName(next_id)});
                 return error.ParseError;
             }
             var saw_l_paren = false;
@@ -5995,7 +5995,7 @@ fn parseCPrimaryExprInner(c: *Context, m: *MacroCtx, scope: *Scope) ParseError!*
             return &group_node.base;
         },
         else => {
-            try m.fail(c, "unable to translate C expr: unexpected token .{}", .{@tagName(tok)});
+            try m.fail(c, "unable to translate C expr: unexpected token .{s}", .{@tagName(tok)});
             return error.ParseError;
         },
     }
diff --git a/src/value.zig b/src/value.zig
index 8180df2f9e..10f58fa44f 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -464,7 +464,7 @@ pub const Value = extern union {
             .ty => return val.castTag(.ty).?.data.format("", options, out_stream),
             .int_type => {
                 const int_type = val.castTag(.int_type).?.data;
-                return out_stream.print("{}{}", .{
+                return out_stream.print("{s}{d}", .{
                     if (int_type.signed) "s" else "u",
                     int_type.bits,
                 });
@@ -507,7 +507,7 @@ pub const Value = extern union {
                 }
                 return out_stream.writeAll("}");
             },
-            .@"error" => return out_stream.print("error.{}", .{val.castTag(.@"error").?.data.name}),
+            .@"error" => return out_stream.print("error.{s}", .{val.castTag(.@"error").?.data.name}),
             .inferred_alloc => return out_stream.writeAll("(inferred allocation value)"),
         };
     }
diff --git a/src/zir.zig b/src/zir.zig
index ce8498d7e8..94e2b24b0c 100644
--- a/src/zir.zig
+++ b/src/zir.zig
@@ -1150,7 +1150,7 @@ pub const Module = struct {
 
         for (self.decls) |decl, i| {
             write.next_instr_index = 0;
-            try stream.print("@{} ", .{decl.name});
+            try stream.print("@{s} ", .{decl.name});
             try write.writeInstToStream(stream, decl.inst);
             try stream.writeByte('\n');
         }
@@ -1206,13 +1206,13 @@ const Writer = struct {
             if (@typeInfo(arg_field.field_type) == .Optional) {
                 if (@field(inst.kw_args, arg_field.name)) |non_optional| {
                     if (need_comma) try stream.writeAll(", ");
-                    try stream.print("{}=", .{arg_field.name});
+                    try stream.print("{s}=", .{arg_field.name});
                     try self.writeParamToStream(stream, &non_optional);
                     need_comma = true;
                 }
             } else {
                 if (need_comma) try stream.writeAll(", ");
-                try stream.print("{}=", .{arg_field.name});
+                try stream.print("{s}=", .{arg_field.name});
                 try self.writeParamToStream(stream, &@field(inst.kw_args, arg_field.name));
                 need_comma = true;
             }
@@ -1334,16 +1334,16 @@ const Writer = struct {
             if (info.index) |i| {
                 try stream.print("%{}", .{info.index});
             } else {
-                try stream.print("@{}", .{info.name});
+                try stream.print("@{s}", .{info.name});
             }
         } else if (inst.cast(Inst.DeclVal)) |decl_val| {
-            try stream.print("@{}", .{decl_val.positionals.name});
+            try stream.print("@{s}", .{decl_val.positionals.name});
         } else if (inst.cast(Inst.DeclValInModule)) |decl_val| {
-            try stream.print("@{}", .{decl_val.positionals.decl.name});
+            try stream.print("@{s}", .{decl_val.positionals.decl.name});
         } else {
             // This should be unreachable in theory, but since ZIR is used for debugging the compiler
             // we output some debug text instead.
-            try stream.print("?{}?", .{@tagName(inst.tag)});
+            try stream.print("?{s}?", .{@tagName(inst.tag)});
         }
     }
 };
@@ -1424,7 +1424,7 @@ const Parser = struct {
                 const decl = try parseInstruction(self, &body_context, ident);
                 const ident_index = body_context.instructions.items.len;
                 if (try body_context.name_map.fetchPut(ident, decl.inst)) |_| {
-                    return self.fail("redefinition of identifier '{}'", .{ident});
+                    return self.fail("redefinition of identifier '{s}'", .{ident});
                 }
                 try body_context.instructions.append(decl.inst);
                 continue;
@@ -1510,7 +1510,7 @@ const Parser = struct {
                     const decl = try parseInstruction(self, null, ident);
                     const ident_index = self.decls.items.len;
                     if (try self.global_name_map.fetchPut(ident, decl.inst)) |_| {
-                        return self.fail("redefinition of identifier '{}'", .{ident});
+                        return self.fail("redefinition of identifier '{s}'", .{ident});
                     }
                     try self.decls.append(self.allocator, decl);
                 },
@@ -1538,7 +1538,7 @@ const Parser = struct {
         for (bytes) |byte| {
             if (self.source[self.i] != byte) {
                 self.i = start;
-                return self.fail("expected '{}'", .{bytes});
+                return self.fail("expected '{s}'", .{bytes});
             }
             self.i += 1;
         }
@@ -1585,7 +1585,7 @@ const Parser = struct {
                 return parseInstructionGeneric(self, field.name, tag.Type(), tag, body_ctx, name, contents_start);
             }
         }
-        return self.fail("unknown instruction '{}'", .{fn_name});
+        return self.fail("unknown instruction '{s}'", .{fn_name});
     }
 
     fn parseInstructionGeneric(
@@ -1621,7 +1621,7 @@ const Parser = struct {
                 self.i += 1;
                 skipSpace(self);
             } else if (self.source[self.i] == ')') {
-                return self.fail("expected positional parameter '{}'", .{arg_field.name});
+                return self.fail("expected positional parameter '{s}'", .{arg_field.name});
             }
             @field(inst_specific.positionals, arg_field.name) = try parseParameterGeneric(
                 self,
@@ -1648,7 +1648,7 @@ const Parser = struct {
                     break;
                 }
             } else {
-                return self.fail("unrecognized keyword parameter: '{}'", .{name});
+                return self.fail("unrecognized keyword parameter: '{s}'", .{name});
             }
             skipSpace(self);
         }
@@ -1672,7 +1672,7 @@ const Parser = struct {
                 ' ', '\n', ',', ')' => {
                     const enum_name = self.source[start..self.i];
                     return std.meta.stringToEnum(T, enum_name) orelse {
-                        return self.fail("tag '{}' not a member of enum '{}'", .{ enum_name, @typeName(T) });
+                        return self.fail("tag '{s}' not a member of enum '{s}'", .{ enum_name, @typeName(T) });
                     };
                 },
                 0 => return self.failByte(0),
@@ -1710,7 +1710,7 @@ const Parser = struct {
             BigIntConst => return self.parseIntegerLiteral(),
             usize => {
                 const big_int = try self.parseIntegerLiteral();
-                return big_int.to(usize) catch |err| return self.fail("integer literal: {}", .{@errorName(err)});
+                return big_int.to(usize) catch |err| return self.fail("integer literal: {s}", .{@errorName(err)});
             },
             TypedValue => return self.fail("'const' is a special instruction; not legal in ZIR text", .{}),
             *IrModule.Decl => return self.fail("'declval_in_module' is a special instruction; not legal in ZIR text", .{}),
@@ -1759,7 +1759,7 @@ const Parser = struct {
             },
             else => @compileError("Unimplemented: ir parseParameterGeneric for type " ++ @typeName(T)),
         }
-        return self.fail("TODO parse parameter {}", .{@typeName(T)});
+        return self.fail("TODO parse parameter {s}", .{@typeName(T)});
     }
 
     fn parseParameterInst(self: *Parser, body_ctx: ?*Body) !*Inst {
@@ -1788,7 +1788,7 @@ const Parser = struct {
             const src = name_start - 1;
             if (local_ref) {
                 self.i = src;
-                return self.fail("unrecognized identifier: {}", .{bad_name});
+                return self.fail("unrecognized identifier: {s}", .{bad_name});
             } else {
                 const declval = try self.arena.allocator.create(Inst.DeclVal);
                 declval.* = .{
@@ -1873,7 +1873,7 @@ pub fn dumpFn(old_module: IrModule, module_fn: *IrModule.Fn) void {
 
     const fn_ty = module_fn.owner_decl.typed_value.most_recent.typed_value.ty;
     _ = ctx.emitFn(module_fn, 0, fn_ty) catch |err| {
-        std.debug.print("unable to dump function: {}\n", .{err});
+        std.debug.print("unable to dump function: {s}\n", .{@errorName(err)});
         return;
     };
     var module = Module{
@@ -2203,7 +2203,7 @@ const EmitZIR = struct {
                         };
                         return self.emitStringLiteral(src, bytes);
                     },
-                    else => |t| std.debug.panic("TODO implement emitTypedValue for pointer to {}", .{@tagName(t)}),
+                    else => |t| std.debug.panic("TODO implement emitTypedValue for pointer to {s}", .{@tagName(t)}),
                 }
             },
             .ComptimeInt => return self.emitComptimeIntVal(src, typed_value.val),
@@ -2274,7 +2274,7 @@ const EmitZIR = struct {
                 };
                 return self.emitUnnamedDecl(&inst.base);
             },
-            else => |t| std.debug.panic("TODO implement emitTypedValue for {}", .{@tagName(t)}),
+            else => |t| std.debug.panic("TODO implement emitTypedValue for {s}", .{@tagName(t)}),
         }
     }
 
@@ -2947,7 +2947,7 @@ pub fn dumpZir(allocator: *Allocator, kind: []const u8, decl_name: [*:0]const u8
     try write.inst_table.ensureCapacity(@intCast(u32, instructions.len));
 
     const stderr = std.io.getStdErr().outStream();
-    try stderr.print("{} {s} {{ // unanalyzed\n", .{ kind, decl_name });
+    try stderr.print("{s} {s} {{ // unanalyzed\n", .{ kind, decl_name });
 
     for (instructions) |inst| {
         const my_i = write.next_instr_index;
@@ -2967,5 +2967,5 @@ pub fn dumpZir(allocator: *Allocator, kind: []const u8, decl_name: [*:0]const u8
         try stderr.writeByte('\n');
     }
 
-    try stderr.print("}} // {} {s}\n\n", .{ kind, decl_name });
+    try stderr.print("}} // {s} {s}\n\n", .{ kind, decl_name });
 }
diff --git a/src/zir_sema.zig b/src/zir_sema.zig
index 629dfa0c9a..72a1b04238 100644
--- a/src/zir_sema.zig
+++ b/src/zir_sema.zig
@@ -274,7 +274,7 @@ pub fn resolveInst(mod: *Module, scope: *Scope, old_inst: *zir.Inst) InnerError!
     const entry = if (old_inst.cast(zir.Inst.DeclVal)) |declval| blk: {
         const decl_name = declval.positionals.name;
         const entry = zir_module.contents.module.findDecl(decl_name) orelse
-            return mod.fail(scope, old_inst.src, "decl '{}' not found", .{decl_name});
+            return mod.fail(scope, old_inst.src, "decl '{s}' not found", .{decl_name});
         break :blk entry;
     } else blk: {
         // If this assert trips, the instruction that was referenced did not get
@@ -564,14 +564,14 @@ fn analyzeInstStr(mod: *Module, scope: *Scope, str_inst: *zir.Inst.Str) InnerErr
 fn analyzeInstExport(mod: *Module, scope: *Scope, export_inst: *zir.Inst.Export) InnerError!*Inst {
     const symbol_name = try resolveConstString(mod, scope, export_inst.positionals.symbol_name);
     const exported_decl = mod.lookupDeclName(scope, export_inst.positionals.decl_name) orelse
-        return mod.fail(scope, export_inst.base.src, "decl '{}' not found", .{export_inst.positionals.decl_name});
+        return mod.fail(scope, export_inst.base.src, "decl '{s}' not found", .{export_inst.positionals.decl_name});
     try mod.analyzeExport(scope, export_inst.base.src, symbol_name, exported_decl);
     return mod.constVoid(scope, export_inst.base.src);
 }
 
 fn analyzeInstCompileError(mod: *Module, scope: *Scope, inst: *zir.Inst.UnOp) InnerError!*Inst {
     const msg = try resolveConstString(mod, scope, inst.positionals.operand);
-    return mod.fail(scope, inst.base.src, "{}", .{msg});
+    return mod.fail(scope, inst.base.src, "{s}", .{msg});
 }
 
 fn analyzeInstArg(mod: *Module, scope: *Scope, inst: *zir.Inst.Arg) InnerError!*Inst {
@@ -918,7 +918,7 @@ fn analyzeInstErrorSet(mod: *Module, scope: *Scope, inst: *zir.Inst.ErrorSet) In
     for (inst.positionals.fields) |field_name| {
         const entry = try mod.getErrorValue(field_name);
         if (payload.data.fields.fetchPutAssumeCapacity(entry.key, entry.value)) |prev| {
-            return mod.fail(scope, inst.base.src, "duplicate error: '{}'", .{field_name});
+            return mod.fail(scope, inst.base.src, "duplicate error: '{s}'", .{field_name});
         }
     }
     // TODO create name in format "error:line:column"
@@ -1068,7 +1068,7 @@ fn analyzeInstFieldPtr(mod: *Module, scope: *Scope, fieldptr: *zir.Inst.FieldPtr
                 return mod.fail(
                     scope,
                     fieldptr.positionals.field_name.src,
-                    "no member named '{}' in '{}'",
+                    "no member named '{s}' in '{}'",
                     .{ field_name, elem_ty },
                 );
             }
@@ -1089,7 +1089,7 @@ fn analyzeInstFieldPtr(mod: *Module, scope: *Scope, fieldptr: *zir.Inst.FieldPtr
                         return mod.fail(
                             scope,
                             fieldptr.positionals.field_name.src,
-                            "no member named '{}' in '{}'",
+                            "no member named '{s}' in '{}'",
                             .{ field_name, elem_ty },
                         );
                     }
@@ -1107,7 +1107,7 @@ fn analyzeInstFieldPtr(mod: *Module, scope: *Scope, fieldptr: *zir.Inst.FieldPtr
                     // TODO resolve inferred error sets
                     const entry = if (val.castTag(.error_set)) |payload|
                         (payload.data.fields.getEntry(field_name) orelse
-                            return mod.fail(scope, fieldptr.base.src, "no error named '{}' in '{}'", .{ field_name, child_type })).*
+                            return mod.fail(scope, fieldptr.base.src, "no error named '{s}' in '{}'", .{ field_name, child_type })).*
                     else
                         try mod.getErrorValue(field_name);
 
@@ -1135,9 +1135,9 @@ fn analyzeInstFieldPtr(mod: *Module, scope: *Scope, fieldptr: *zir.Inst.FieldPtr
                     }
 
                     if (&container_scope.file_scope.base == mod.root_scope) {
-                        return mod.fail(scope, fieldptr.base.src, "root source file has no member called '{}'", .{field_name});
+                        return mod.fail(scope, fieldptr.base.src, "root source file has no member called '{s}'", .{field_name});
                     } else {
-                        return mod.fail(scope, fieldptr.base.src, "container '{}' has no member called '{}'", .{ child_type, field_name });
+                        return mod.fail(scope, fieldptr.base.src, "container '{}' has no member called '{s}'", .{ child_type, field_name });
                     }
                 },
                 else => return mod.fail(scope, fieldptr.base.src, "type '{}' does not support field access", .{child_type}),
@@ -1503,14 +1503,14 @@ fn analyzeInstImport(mod: *Module, scope: *Scope, inst: *zir.Inst.UnOp) InnerErr
 
     const file_scope = mod.analyzeImport(scope, inst.base.src, operand) catch |err| switch (err) {
         error.ImportOutsidePkgPath => {
-            return mod.fail(scope, inst.base.src, "import of file outside package path: '{}'", .{operand});
+            return mod.fail(scope, inst.base.src, "import of file outside package path: '{s}'", .{operand});
         },
         error.FileNotFound => {
-            return mod.fail(scope, inst.base.src, "unable to find '{}'", .{operand});
+            return mod.fail(scope, inst.base.src, "unable to find '{s}'", .{operand});
         },
         else => {
             // TODO user friendly error to string
-            return mod.fail(scope, inst.base.src, "unable to open '{}': {}", .{ operand, @errorName(err) });
+            return mod.fail(scope, inst.base.src, "unable to open '{s}': {s}", .{ operand, @errorName(err) });
         },
     };
     return mod.constType(scope, inst.base.src, file_scope.root_container.ty);
@@ -1637,7 +1637,7 @@ fn analyzeInstArithmetic(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) Inn
     const is_float = scalar_tag == .Float or scalar_tag == .ComptimeFloat;
 
     if (!is_int and !(is_float and floatOpAllowed(inst.base.tag))) {
-        return mod.fail(scope, inst.base.src, "invalid operands to binary expression: '{}' and '{}'", .{ @tagName(lhs.ty.zigTypeTag()), @tagName(rhs.ty.zigTypeTag()) });
+        return mod.fail(scope, inst.base.src, "invalid operands to binary expression: '{s}' and '{s}'", .{ @tagName(lhs.ty.zigTypeTag()), @tagName(rhs.ty.zigTypeTag()) });
     }
 
     if (casted_lhs.value()) |lhs_val| {
@@ -1656,7 +1656,7 @@ fn analyzeInstArithmetic(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) Inn
     const ir_tag = switch (inst.base.tag) {
         .add => Inst.Tag.add,
         .sub => Inst.Tag.sub,
-        else => return mod.fail(scope, inst.base.src, "TODO implement arithmetic for operand '{}''", .{@tagName(inst.base.tag)}),
+        else => return mod.fail(scope, inst.base.src, "TODO implement arithmetic for operand '{s}''", .{@tagName(inst.base.tag)}),
     };
 
     return mod.addBinOp(b, inst.base.src, scalar_type, ir_tag, casted_lhs, casted_rhs);
@@ -1689,7 +1689,7 @@ fn analyzeInstComptimeOp(mod: *Module, scope: *Scope, res_type: Type, inst: *zir
                 mod.floatSub(scope, res_type, inst.base.src, lhs_val, rhs_val);
             break :blk val;
         },
-        else => return mod.fail(scope, inst.base.src, "TODO Implement arithmetic operand '{}'", .{@tagName(inst.base.tag)}),
+        else => return mod.fail(scope, inst.base.src, "TODO Implement arithmetic operand '{s}'", .{@tagName(inst.base.tag)}),
     };
 
     return mod.constInst(scope, inst.base.src, .{
@@ -1781,7 +1781,7 @@ fn analyzeInstCmp(
         return mod.fail(scope, inst.base.src, "TODO implement equality comparison between a union's tag value and an enum literal", .{});
     } else if (lhs_ty_tag == .ErrorSet and rhs_ty_tag == .ErrorSet) {
         if (!is_equality_cmp) {
-            return mod.fail(scope, inst.base.src, "{} operator not allowed for errors", .{@tagName(op)});
+            return mod.fail(scope, inst.base.src, "{s} operator not allowed for errors", .{@tagName(op)});
         }
         return mod.fail(scope, inst.base.src, "TODO implement equality comparison between errors", .{});
     } else if (lhs.ty.isNumeric() and rhs.ty.isNumeric()) {
@@ -1962,7 +1962,7 @@ fn analyzeDeclVal(mod: *Module, scope: *Scope, inst: *zir.Inst.DeclVal) InnerErr
     const decl_name = inst.positionals.name;
     const zir_module = scope.namespace().cast(Scope.ZIRModule).?;
     const src_decl = zir_module.contents.module.findDecl(decl_name) orelse
-        return mod.fail(scope, inst.base.src, "use of undeclared identifier '{}'", .{decl_name});
+        return mod.fail(scope, inst.base.src, "use of undeclared identifier '{s}'", .{decl_name});
 
     const decl = try resolveCompleteZirDecl(mod, scope, src_decl.decl);
 

From 4420afe64d5ae03565b51dcec55ce9dd7351d0ee Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 13:28:38 +0100
Subject: [PATCH 09/16] tests: Use {s} instead of {} when formatting strings

---
 build.zig                        | 205 +++++++++++++++++++++++++++++--
 lib/std/special/build_runner.zig |  14 +--
 test/src/compare_output.zig      |   6 +-
 test/src/run_translated_c.zig    |   8 +-
 test/src/translate_c.zig         |   2 +-
 test/tests.zig                   |  62 +++++-----
 6 files changed, 243 insertions(+), 54 deletions(-)

diff --git a/build.zig b/build.zig
index fe588ea2cb..ab230d8f46 100644
--- a/build.zig
+++ b/build.zig
@@ -224,7 +224,7 @@ pub fn build(b: *Builder) !void {
 
     const opt_version_string = b.option([]const u8, "version-string", "Override Zig version string. Default is to find out with git.");
     const version = if (opt_version_string) |version| version else v: {
-        const version_string = b.fmt("{}.{}.{}", .{ zig_version.major, zig_version.minor, zig_version.patch });
+        const version_string = b.fmt("{d}.{d}.{d}", .{ zig_version.major, zig_version.minor, zig_version.patch });
 
         var code: u8 = undefined;
         const git_describe_untrimmed = b.execAllowFail(&[_][]const u8{
@@ -238,7 +238,7 @@ pub fn build(b: *Builder) !void {
             0 => {
                 // Tagged release version (e.g. 0.7.0).
                 if (!mem.eql(u8, git_describe, version_string)) {
-                    std.debug.print("Zig version '{}' does not match Git tag '{}'\n", .{ version_string, git_describe });
+                    std.debug.print("Zig version '{s}' does not match Git tag '{s}'\n", .{ version_string, git_describe });
                     std.process.exit(1);
                 }
                 break :v version_string;
@@ -258,15 +258,15 @@ pub fn build(b: *Builder) !void {
 
                 // Check that the commit hash is prefixed with a 'g' (a Git convention).
                 if (commit_id.len < 1 or commit_id[0] != 'g') {
-                    std.debug.print("Unexpected `git describe` output: {}\n", .{git_describe});
+                    std.debug.print("Unexpected `git describe` output: {s}\n", .{git_describe});
                     break :v version_string;
                 }
 
                 // The version is reformatted in accordance with the https://semver.org specification.
-                break :v b.fmt("{}-dev.{}+{}", .{ version_string, commit_height, commit_id[1..] });
+                break :v b.fmt("{s}-dev.{s}+{s}", .{ version_string, commit_height, commit_id[1..] });
             },
             else => {
-                std.debug.print("Unexpected `git describe` output: {}\n", .{git_describe});
+                std.debug.print("Unexpected `git describe` output: {s}\n", .{git_describe});
                 break :v version_string;
             },
         }
@@ -359,6 +359,195 @@ pub fn build(b: *Builder) !void {
     test_step.dependOn(docs_step);
 }
 
+fn dependOnLib(b: *Builder, lib_exe_obj: anytype, dep: LibraryDep) void {
+    for (dep.libdirs.items) |lib_dir| {
+        lib_exe_obj.addLibPath(lib_dir);
+    }
+    const lib_dir = fs.path.join(
+        b.allocator,
+        &[_][]const u8{ dep.prefix, "lib" },
+    ) catch unreachable;
+    for (dep.system_libs.items) |lib| {
+        const static_bare_name = if (mem.eql(u8, lib, "curses"))
+            @as([]const u8, "libncurses.a")
+        else
+            b.fmt("lib{s}.a", .{lib});
+        const static_lib_name = fs.path.join(
+            b.allocator,
+            &[_][]const u8{ lib_dir, static_bare_name },
+        ) catch unreachable;
+        const have_static = fileExists(static_lib_name) catch unreachable;
+        if (have_static) {
+            lib_exe_obj.addObjectFile(static_lib_name);
+        } else {
+            lib_exe_obj.linkSystemLibrary(lib);
+        }
+    }
+    for (dep.libs.items) |lib| {
+        lib_exe_obj.addObjectFile(lib);
+    }
+    for (dep.includes.items) |include_path| {
+        lib_exe_obj.addIncludeDir(include_path);
+    }
+}
+
+fn fileExists(filename: []const u8) !bool {
+    fs.cwd().access(filename, .{}) catch |err| switch (err) {
+        error.FileNotFound => return false,
+        else => return err,
+    };
+    return true;
+}
+
+fn addCppLib(b: *Builder, lib_exe_obj: anytype, cmake_binary_dir: []const u8, lib_name: []const u8) void {
+    lib_exe_obj.addObjectFile(fs.path.join(b.allocator, &[_][]const u8{
+        cmake_binary_dir,
+        "zigcpp",
+        b.fmt("{s}{s}{s}", .{ lib_exe_obj.target.libPrefix(), lib_name, lib_exe_obj.target.staticLibSuffix() }),
+    }) catch unreachable);
+}
+
+const LibraryDep = struct {
+    prefix: []const u8,
+    libdirs: ArrayList([]const u8),
+    libs: ArrayList([]const u8),
+    system_libs: ArrayList([]const u8),
+    includes: ArrayList([]const u8),
+};
+
+fn findLLVM(b: *Builder, llvm_config_exe: []const u8) !LibraryDep {
+    const shared_mode = try b.exec(&[_][]const u8{ llvm_config_exe, "--shared-mode" });
+    const is_static = mem.startsWith(u8, shared_mode, "static");
+    const libs_output = if (is_static)
+        try b.exec(&[_][]const u8{
+            llvm_config_exe,
+            "--libfiles",
+            "--system-libs",
+        })
+    else
+        try b.exec(&[_][]const u8{
+            llvm_config_exe,
+            "--libs",
+        });
+    const includes_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--includedir" });
+    const libdir_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--libdir" });
+    const prefix_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--prefix" });
+
+    var result = LibraryDep{
+        .prefix = mem.tokenize(prefix_output, " \r\n").next().?,
+        .libs = ArrayList([]const u8).init(b.allocator),
+        .system_libs = ArrayList([]const u8).init(b.allocator),
+        .includes = ArrayList([]const u8).init(b.allocator),
+        .libdirs = ArrayList([]const u8).init(b.allocator),
+    };
+    {
+        var it = mem.tokenize(libs_output, " \r\n");
+        while (it.next()) |lib_arg| {
+            if (mem.startsWith(u8, lib_arg, "-l")) {
+                try result.system_libs.append(lib_arg[2..]);
+            } else {
+                if (fs.path.isAbsolute(lib_arg)) {
+                    try result.libs.append(lib_arg);
+                } else {
+                    var lib_arg_copy = lib_arg;
+                    if (mem.endsWith(u8, lib_arg, ".lib")) {
+                        lib_arg_copy = lib_arg[0 .. lib_arg.len - 4];
+                    }
+                    try result.system_libs.append(lib_arg_copy);
+                }
+            }
+        }
+    }
+    {
+        var it = mem.tokenize(includes_output, " \r\n");
+        while (it.next()) |include_arg| {
+            if (mem.startsWith(u8, include_arg, "-I")) {
+                try result.includes.append(include_arg[2..]);
+            } else {
+                try result.includes.append(include_arg);
+            }
+        }
+    }
+    {
+        var it = mem.tokenize(libdir_output, " \r\n");
+        while (it.next()) |libdir| {
+            if (mem.startsWith(u8, libdir, "-L")) {
+                try result.libdirs.append(libdir[2..]);
+            } else {
+                try result.libdirs.append(libdir);
+            }
+        }
+    }
+    return result;
+}
+
+fn configureStage2(b: *Builder, exe: anytype, ctx: Context, need_cpp_includes: bool) !void {
+    exe.addIncludeDir("src");
+    exe.addIncludeDir(ctx.cmake_binary_dir);
+    addCppLib(b, exe, ctx.cmake_binary_dir, "zigcpp");
+    assert(ctx.lld_include_dir.len != 0);
+    exe.addIncludeDir(ctx.lld_include_dir);
+    {
+        var it = mem.tokenize(ctx.lld_libraries, ";");
+        while (it.next()) |lib| {
+            exe.addObjectFile(lib);
+        }
+    }
+    {
+        var it = mem.tokenize(ctx.clang_libraries, ";");
+        while (it.next()) |lib| {
+            exe.addObjectFile(lib);
+        }
+    }
+    dependOnLib(b, exe, ctx.llvm);
+
+    // Boy, it sure would be nice to simply linkSystemLibrary("c++") and rely on zig's
+    // ability to provide libc++ right? Well thanks to C++ not having a stable ABI this
+    // will cause linker errors. It would work in the situation when `zig cc` is used to
+    // build LLVM, Clang, and LLD, however when depending on them as system libraries, system
+    // libc++ must be used.
+    const cross_compile = false; // TODO
+    if (cross_compile) {
+        // In this case we assume that zig cc was used to build the LLVM, Clang, LLD dependencies.
+        exe.linkSystemLibrary("c++");
+    } else {
+        if (exe.target.getOsTag() == .linux) {
+            // First we try to static link against gcc libstdc++. If that doesn't work,
+            // we fall back to -lc++ and cross our fingers.
+            addCxxKnownPath(b, ctx, exe, "libstdc++.a", "", need_cpp_includes) catch |err| switch (err) {
+                error.RequiredLibraryNotFound => {
+                    exe.linkSystemLibrary("c++");
+                },
+                else => |e| return e,
+            };
+
+            exe.linkSystemLibrary("pthread");
+        } else if (exe.target.isFreeBSD()) {
+            try addCxxKnownPath(b, ctx, exe, "libc++.a", null, need_cpp_includes);
+            exe.linkSystemLibrary("pthread");
+        } else if (exe.target.isDarwin()) {
+            if (addCxxKnownPath(b, ctx, exe, "libgcc_eh.a", "", need_cpp_includes)) {
+                // Compiler is GCC.
+                try addCxxKnownPath(b, ctx, exe, "libstdc++.a", null, need_cpp_includes);
+                exe.linkSystemLibrary("pthread");
+                // TODO LLD cannot perform this link.
+                // Set ZIG_SYSTEM_LINKER_HACK env var to use system linker ld instead.
+                // See https://github.com/ziglang/zig/issues/1535
+            } else |err| switch (err) {
+                error.RequiredLibraryNotFound => {
+                    // System compiler, not gcc.
+                    exe.linkSystemLibrary("c++");
+                },
+                else => |e| return e,
+            }
+        }
+
+        if (ctx.dia_guids_lib.len != 0) {
+            exe.addObjectFile(ctx.dia_guids_lib);
+        }
+    }
+}
+
 fn addCxxKnownPath(
     b: *Builder,
     ctx: CMakeConfig,
@@ -369,14 +558,14 @@ fn addCxxKnownPath(
 ) !void {
     const path_padded = try b.exec(&[_][]const u8{
         ctx.cxx_compiler,
-        b.fmt("-print-file-name={}", .{objname}),
+        b.fmt("-print-file-name={s}", .{objname}),
     });
     const path_unpadded = mem.tokenize(path_padded, "\r\n").next().?;
     if (mem.eql(u8, path_unpadded, objname)) {
         if (errtxt) |msg| {
-            warn("{}", .{msg});
+            warn("{s}", .{msg});
         } else {
-            warn("Unable to determine path to {}\n", .{objname});
+            warn("Unable to determine path to {s}\n", .{objname});
         }
         return error.RequiredLibraryNotFound;
     }
diff --git a/lib/std/special/build_runner.zig b/lib/std/special/build_runner.zig
index e3e90e7574..f2fa2dc3b8 100644
--- a/lib/std/special/build_runner.zig
+++ b/lib/std/special/build_runner.zig
@@ -98,7 +98,7 @@ pub fn main() !void {
                     return usageAndErr(builder, false, stderr_stream);
                 };
                 builder.color = std.meta.stringToEnum(@TypeOf(builder.color), next_arg) orelse {
-                    warn("expected [auto|on|off] after --color, found '{}'", .{next_arg});
+                    warn("expected [auto|on|off] after --color, found '{s}'", .{next_arg});
                     return usageAndErr(builder, false, stderr_stream);
                 };
             } else if (mem.eql(u8, arg, "--override-lib-dir")) {
@@ -126,7 +126,7 @@ pub fn main() !void {
                 builder.args = argsRest(args, arg_idx);
                 break;
             } else {
-                warn("Unrecognized argument: {}\n\n", .{arg});
+                warn("Unrecognized argument: {s}\n\n", .{arg});
                 return usageAndErr(builder, false, stderr_stream);
             }
         } else {
@@ -168,7 +168,7 @@ fn usage(builder: *Builder, already_ran_build: bool, out_stream: anytype) !void
     }
 
     try out_stream.print(
-        \\Usage: {} build [steps] [options]
+        \\Usage: {s} build [steps] [options]
         \\
         \\Steps:
         \\
@@ -177,10 +177,10 @@ fn usage(builder: *Builder, already_ran_build: bool, out_stream: anytype) !void
     const allocator = builder.allocator;
     for (builder.top_level_steps.items) |top_level_step| {
         const name = if (&top_level_step.step == builder.default_step)
-            try fmt.allocPrint(allocator, "{} (default)", .{top_level_step.step.name})
+            try fmt.allocPrint(allocator, "{s} (default)", .{top_level_step.step.name})
         else
             top_level_step.step.name;
-        try out_stream.print("  {s:<27} {}\n", .{ name, top_level_step.description });
+        try out_stream.print("  {s:<27} {s}\n", .{ name, top_level_step.description });
     }
 
     try out_stream.writeAll(
@@ -200,12 +200,12 @@ fn usage(builder: *Builder, already_ran_build: bool, out_stream: anytype) !void
         try out_stream.print("  (none)\n", .{});
     } else {
         for (builder.available_options_list.items) |option| {
-            const name = try fmt.allocPrint(allocator, "  -D{}=[{}]", .{
+            const name = try fmt.allocPrint(allocator, "  -D{s}=[{s}]", .{
                 option.name,
                 Builder.typeIdName(option.type_id),
             });
             defer allocator.free(name);
-            try out_stream.print("{s:<29} {}\n", .{ name, option.description });
+            try out_stream.print("{s:<29} {s}\n", .{ name, option.description });
         }
     }
 
diff --git a/test/src/compare_output.zig b/test/src/compare_output.zig
index f78d6744e1..1cde470887 100644
--- a/test/src/compare_output.zig
+++ b/test/src/compare_output.zig
@@ -97,7 +97,7 @@ pub const CompareOutputContext = struct {
 
         switch (case.special) {
             Special.Asm => {
-                const annotated_case_name = fmt.allocPrint(self.b.allocator, "assemble-and-link {}", .{
+                const annotated_case_name = fmt.allocPrint(self.b.allocator, "assemble-and-link {s}", .{
                     case.name,
                 }) catch unreachable;
                 if (self.test_filter) |filter| {
@@ -116,7 +116,7 @@ pub const CompareOutputContext = struct {
             },
             Special.None => {
                 for (self.modes) |mode| {
-                    const annotated_case_name = fmt.allocPrint(self.b.allocator, "{} {} ({})", .{
+                    const annotated_case_name = fmt.allocPrint(self.b.allocator, "{s} {s} ({s})", .{
                         "compare-output",
                         case.name,
                         @tagName(mode),
@@ -141,7 +141,7 @@ pub const CompareOutputContext = struct {
                 }
             },
             Special.RuntimeSafety => {
-                const annotated_case_name = fmt.allocPrint(self.b.allocator, "safety {}", .{case.name}) catch unreachable;
+                const annotated_case_name = fmt.allocPrint(self.b.allocator, "safety {s}", .{case.name}) catch unreachable;
                 if (self.test_filter) |filter| {
                     if (mem.indexOf(u8, annotated_case_name, filter) == null) return;
                 }
diff --git a/test/src/run_translated_c.zig b/test/src/run_translated_c.zig
index 06990241cc..1de329112c 100644
--- a/test/src/run_translated_c.zig
+++ b/test/src/run_translated_c.zig
@@ -77,7 +77,7 @@ pub const RunTranslatedCContext = struct {
     pub fn addCase(self: *RunTranslatedCContext, case: *const TestCase) void {
         const b = self.b;
 
-        const annotated_case_name = fmt.allocPrint(self.b.allocator, "run-translated-c {}", .{case.name}) catch unreachable;
+        const annotated_case_name = fmt.allocPrint(self.b.allocator, "run-translated-c {s}", .{case.name}) catch unreachable;
         if (self.test_filter) |filter| {
             if (mem.indexOf(u8, annotated_case_name, filter) == null) return;
         }
@@ -92,13 +92,13 @@ pub const RunTranslatedCContext = struct {
                 .basename = case.sources.items[0].filename,
             },
         });
-        translate_c.step.name = b.fmt("{} translate-c", .{annotated_case_name});
+        translate_c.step.name = b.fmt("{s} translate-c", .{annotated_case_name});
         const exe = translate_c.addExecutable();
         exe.setTarget(self.target);
-        exe.step.name = b.fmt("{} build-exe", .{annotated_case_name});
+        exe.step.name = b.fmt("{s} build-exe", .{annotated_case_name});
         exe.linkLibC();
         const run = exe.run();
-        run.step.name = b.fmt("{} run", .{annotated_case_name});
+        run.step.name = b.fmt("{s} run", .{annotated_case_name});
         if (!case.allow_warnings) {
             run.expectStdErrEqual("");
         }
diff --git a/test/src/translate_c.zig b/test/src/translate_c.zig
index 405c5954ba..c43f326926 100644
--- a/test/src/translate_c.zig
+++ b/test/src/translate_c.zig
@@ -99,7 +99,7 @@ pub const TranslateCContext = struct {
         const b = self.b;
 
         const translate_c_cmd = "translate-c";
-        const annotated_case_name = fmt.allocPrint(self.b.allocator, "{} {}", .{ translate_c_cmd, case.name }) catch unreachable;
+        const annotated_case_name = fmt.allocPrint(self.b.allocator, "{s} {s}", .{ translate_c_cmd, case.name }) catch unreachable;
         if (self.test_filter) |filter| {
             if (mem.indexOf(u8, annotated_case_name, filter) == null) return;
         }
diff --git a/test/tests.zig b/test/tests.zig
index 250c1cc4ea..5ee381e5c2 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -482,7 +482,7 @@ pub fn addPkgTests(
     is_wasmtime_enabled: bool,
     glibc_dir: ?[]const u8,
 ) *build.Step {
-    const step = b.step(b.fmt("test-{}", .{name}), desc);
+    const step = b.step(b.fmt("test-{s}", .{name}), desc);
 
     for (test_targets) |test_target| {
         if (skip_non_native and !test_target.target.isNative())
@@ -523,7 +523,7 @@ pub fn addPkgTests(
 
         const these_tests = b.addTest(root_src);
         const single_threaded_txt = if (test_target.single_threaded) "single" else "multi";
-        these_tests.setNamePrefix(b.fmt("{}-{}-{}-{}-{} ", .{
+        these_tests.setNamePrefix(b.fmt("{s}-{s}-{s}-{s}-{s} ", .{
             name,
             triple_prefix,
             @tagName(test_target.mode),
@@ -570,7 +570,7 @@ pub const StackTracesContext = struct {
             const expect_for_mode = expect[@enumToInt(mode)];
             if (expect_for_mode.len == 0) continue;
 
-            const annotated_case_name = fmt.allocPrint(self.b.allocator, "{} {} ({})", .{
+            const annotated_case_name = fmt.allocPrint(self.b.allocator, "{s} {s} ({s})", .{
                 "stack-trace",
                 name,
                 @tagName(mode),
@@ -637,7 +637,7 @@ pub const StackTracesContext = struct {
             defer args.deinit();
             args.append(full_exe_path) catch unreachable;
 
-            warn("Test {}/{} {}...", .{ self.test_index + 1, self.context.test_index, self.name });
+            warn("Test {d}/{d} {s}...", .{ self.test_index + 1, self.context.test_index, self.name });
 
             const child = std.ChildProcess.init(args.items, b.allocator) catch unreachable;
             defer child.deinit();
@@ -650,7 +650,7 @@ pub const StackTracesContext = struct {
             if (b.verbose) {
                 printInvocation(args.items);
             }
-            child.spawn() catch |err| debug.panic("Unable to spawn {}: {}\n", .{ full_exe_path, @errorName(err) });
+            child.spawn() catch |err| debug.panic("Unable to spawn {s}: {s}\n", .{ full_exe_path, @errorName(err) });
 
             const stdout = child.stdout.?.inStream().readAllAlloc(b.allocator, max_stdout_size) catch unreachable;
             defer b.allocator.free(stdout);
@@ -659,14 +659,14 @@ pub const StackTracesContext = struct {
             var stderr = stderrFull;
 
             const term = child.wait() catch |err| {
-                debug.panic("Unable to spawn {}: {}\n", .{ full_exe_path, @errorName(err) });
+                debug.panic("Unable to spawn {s}: {s}\n", .{ full_exe_path, @errorName(err) });
             };
 
             switch (term) {
                 .Exited => |code| {
                     const expect_code: u32 = 1;
                     if (code != expect_code) {
-                        warn("Process {} exited with error code {} but expected code {}\n", .{
+                        warn("Process {s} exited with error code {d} but expected code {d}\n", .{
                             full_exe_path,
                             code,
                             expect_code,
@@ -676,17 +676,17 @@ pub const StackTracesContext = struct {
                     }
                 },
                 .Signal => |signum| {
-                    warn("Process {} terminated on signal {}\n", .{ full_exe_path, signum });
+                    warn("Process {s} terminated on signal {d}\n", .{ full_exe_path, signum });
                     printInvocation(args.items);
                     return error.TestFailed;
                 },
                 .Stopped => |signum| {
-                    warn("Process {} stopped on signal {}\n", .{ full_exe_path, signum });
+                    warn("Process {s} stopped on signal {d}\n", .{ full_exe_path, signum });
                     printInvocation(args.items);
                     return error.TestFailed;
                 },
                 .Unknown => |code| {
-                    warn("Process {} terminated unexpectedly with error code {}\n", .{ full_exe_path, code });
+                    warn("Process {s} terminated unexpectedly with error code {d}\n", .{ full_exe_path, code });
                     printInvocation(args.items);
                     return error.TestFailed;
                 },
@@ -732,9 +732,9 @@ pub const StackTracesContext = struct {
                 warn(
                     \\
                     \\========= Expected this output: =========
-                    \\{}
+                    \\{s}
                     \\================================================
-                    \\{}
+                    \\{s}
                     \\
                 , .{ self.expect_output, got });
                 return error.TestFailed;
@@ -856,7 +856,7 @@ pub const CompileErrorContext = struct {
             zig_args.append("-O") catch unreachable;
             zig_args.append(@tagName(self.build_mode)) catch unreachable;
 
-            warn("Test {}/{} {}...", .{ self.test_index + 1, self.context.test_index, self.name });
+            warn("Test {d}/{d} {s}...", .{ self.test_index + 1, self.context.test_index, self.name });
 
             if (b.verbose) {
                 printInvocation(zig_args.items);
@@ -870,7 +870,7 @@ pub const CompileErrorContext = struct {
             child.stdout_behavior = .Pipe;
             child.stderr_behavior = .Pipe;
 
-            child.spawn() catch |err| debug.panic("Unable to spawn {}: {}\n", .{ zig_args.items[0], @errorName(err) });
+            child.spawn() catch |err| debug.panic("Unable to spawn {s}: {s}\n", .{ zig_args.items[0], @errorName(err) });
 
             var stdout_buf = ArrayList(u8).init(b.allocator);
             var stderr_buf = ArrayList(u8).init(b.allocator);
@@ -879,7 +879,7 @@ pub const CompileErrorContext = struct {
             child.stderr.?.inStream().readAllArrayList(&stderr_buf, max_stdout_size) catch unreachable;
 
             const term = child.wait() catch |err| {
-                debug.panic("Unable to spawn {}: {}\n", .{ zig_args.items[0], @errorName(err) });
+                debug.panic("Unable to spawn {s}: {s}\n", .{ zig_args.items[0], @errorName(err) });
             };
             switch (term) {
                 .Exited => |code| {
@@ -889,7 +889,7 @@ pub const CompileErrorContext = struct {
                     }
                 },
                 else => {
-                    warn("Process {} terminated unexpectedly\n", .{b.zig_exe});
+                    warn("Process {s} terminated unexpectedly\n", .{b.zig_exe});
                     printInvocation(zig_args.items);
                     return error.TestFailed;
                 },
@@ -903,7 +903,7 @@ pub const CompileErrorContext = struct {
                     \\
                     \\Expected empty stdout, instead found:
                     \\================================================
-                    \\{}
+                    \\{s}
                     \\================================================
                     \\
                 , .{stdout});
@@ -926,7 +926,7 @@ pub const CompileErrorContext = struct {
                 if (!ok) {
                     warn("\n======== Expected these compile errors: ========\n", .{});
                     for (self.case.expected_errors.items) |expected| {
-                        warn("{}\n", .{expected});
+                        warn("{s}\n", .{expected});
                     }
                 }
             } else {
@@ -935,7 +935,7 @@ pub const CompileErrorContext = struct {
                         warn(
                             \\
                             \\=========== Expected compile error: ============
-                            \\{}
+                            \\{s}
                             \\
                         , .{expected});
                         ok = false;
@@ -947,7 +947,7 @@ pub const CompileErrorContext = struct {
             if (!ok) {
                 warn(
                     \\================= Full output: =================
-                    \\{}
+                    \\{s}
                     \\
                 , .{stderr});
                 return error.TestFailed;
@@ -1023,7 +1023,7 @@ pub const CompileErrorContext = struct {
     pub fn addCase(self: *CompileErrorContext, case: *const TestCase) void {
         const b = self.b;
 
-        const annotated_case_name = fmt.allocPrint(self.b.allocator, "compile-error {}", .{
+        const annotated_case_name = fmt.allocPrint(self.b.allocator, "compile-error {s}", .{
             case.name,
         }) catch unreachable;
         if (self.test_filter) |filter| {
@@ -1058,7 +1058,7 @@ pub const StandaloneContext = struct {
     pub fn addBuildFile(self: *StandaloneContext, build_file: []const u8) void {
         const b = self.b;
 
-        const annotated_case_name = b.fmt("build {} (Debug)", .{build_file});
+        const annotated_case_name = b.fmt("build {s} (Debug)", .{build_file});
         if (self.test_filter) |filter| {
             if (mem.indexOf(u8, annotated_case_name, filter) == null) return;
         }
@@ -1079,7 +1079,7 @@ pub const StandaloneContext = struct {
 
         const run_cmd = b.addSystemCommand(zig_args.items);
 
-        const log_step = b.addLog("PASS {}\n", .{annotated_case_name});
+        const log_step = b.addLog("PASS {s}\n", .{annotated_case_name});
         log_step.step.dependOn(&run_cmd.step);
 
         self.step.dependOn(&log_step.step);
@@ -1089,7 +1089,7 @@ pub const StandaloneContext = struct {
         const b = self.b;
 
         for (self.modes) |mode| {
-            const annotated_case_name = fmt.allocPrint(self.b.allocator, "build {} ({})", .{
+            const annotated_case_name = fmt.allocPrint(self.b.allocator, "build {s} ({s})", .{
                 root_src,
                 @tagName(mode),
             }) catch unreachable;
@@ -1103,7 +1103,7 @@ pub const StandaloneContext = struct {
                 exe.linkSystemLibrary("c");
             }
 
-            const log_step = b.addLog("PASS {}\n", .{annotated_case_name});
+            const log_step = b.addLog("PASS {s}\n", .{annotated_case_name});
             log_step.step.dependOn(&exe.step);
 
             self.step.dependOn(&log_step.step);
@@ -1172,7 +1172,7 @@ pub const GenHContext = struct {
             const self = @fieldParentPtr(GenHCmpOutputStep, "step", step);
             const b = self.context.b;
 
-            warn("Test {}/{} {}...", .{ self.test_index + 1, self.context.test_index, self.name });
+            warn("Test {d}/{d} {s}...", .{ self.test_index + 1, self.context.test_index, self.name });
 
             const full_h_path = self.obj.getOutputHPath();
             const actual_h = try io.readFileAlloc(b.allocator, full_h_path);
@@ -1182,9 +1182,9 @@ pub const GenHContext = struct {
                     warn(
                         \\
                         \\========= Expected this output: ================
-                        \\{}
+                        \\{s}
                         \\========= But found: ===========================
-                        \\{}
+                        \\{s}
                         \\
                     , .{ expected_line, actual_h });
                     return error.TestFailed;
@@ -1196,7 +1196,7 @@ pub const GenHContext = struct {
 
     fn printInvocation(args: []const []const u8) void {
         for (args) |arg| {
-            warn("{} ", .{arg});
+            warn("{s} ", .{arg});
         }
         warn("\n", .{});
     }
@@ -1232,7 +1232,7 @@ pub const GenHContext = struct {
         const b = self.b;
 
         const mode = builtin.Mode.Debug;
-        const annotated_case_name = fmt.allocPrint(self.b.allocator, "gen-h {} ({})", .{ case.name, @tagName(mode) }) catch unreachable;
+        const annotated_case_name = fmt.allocPrint(self.b.allocator, "gen-h {s} ({s})", .{ case.name, @tagName(mode) }) catch unreachable;
         if (self.test_filter) |filter| {
             if (mem.indexOf(u8, annotated_case_name, filter) == null) return;
         }
@@ -1253,7 +1253,7 @@ pub const GenHContext = struct {
 
 fn printInvocation(args: []const []const u8) void {
     for (args) |arg| {
-        warn("{} ", .{arg});
+        warn("{s} ", .{arg});
     }
     warn("\n", .{});
 }

From 1ca2deca33e5ee489e12bd71a34ec3e4a2e1255f Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 15:43:28 +0100
Subject: [PATCH 10/16] std: Disable the special casing of {} for u8
 slices/arrays

Unless {s} is specified the contents won't be treated as a string.
---
 lib/std/fmt.zig | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 7adee00928..54d96168e2 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -504,7 +504,9 @@ pub fn formatType(
             .One => switch (@typeInfo(ptr_info.child)) {
                 .Array => |info| {
                     if (info.child == u8) {
-                        return formatText(value, fmt, options, writer);
+                        if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
+                            return formatText(value, fmt, options, writer);
+                        }
                     }
                     return format(writer, "{s}@{x}", .{ @typeName(ptr_info.child), @ptrToInt(value) });
                 },
@@ -529,7 +531,7 @@ pub fn formatType(
                     return writer.writeAll("{ ... }");
                 }
                 if (ptr_info.child == u8) {
-                    if (fmt.len == 0 or comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
+                    if (fmt.len > 0 and comptime mem.indexOfScalar(u8, "sxXeEzZ", fmt[0]) != null) {
                         return formatText(value, fmt, options, writer);
                     }
                 }

From d2f6fa1608f31cbd7137f81b5dd6df2977766eae Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 17:06:52 +0100
Subject: [PATCH 11/16] Fix more stray uses of {} for formatting strings

---
 src/Module.zig                    | 14 +++++++-------
 src/link/Elf.zig                  |  4 ++--
 src/test.zig                      |  2 +-
 test/compare_output.zig           |  4 ++--
 test/stage1/behavior/async_fn.zig |  3 ++-
 5 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/Module.zig b/src/Module.zig
index e0042d6c4d..0d03703dcb 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -918,7 +918,7 @@ pub fn ensureDeclAnalyzed(self: *Module, decl: *Decl) InnerError!void {
         .complete => return,
 
         .outdated => blk: {
-            log.debug("re-analyzing {}\n", .{decl.name});
+            log.debug("re-analyzing {s}\n", .{decl.name});
 
             // The exports this Decl performs will be re-discovered, so we remove them here
             // prior to re-analysis.
@@ -1663,7 +1663,7 @@ pub fn analyzeContainer(self: *Module, container_scope: *Scope.Container) !void
     // Handle explicitly deleted decls from the source code. Not to be confused
     // with when we delete decls because they are no longer referenced.
     for (deleted_decls.items()) |entry| {
-        log.debug("noticed '{}' deleted from source\n", .{entry.key.name});
+        log.debug("noticed '{s}' deleted from source\n", .{entry.key.name});
         try self.deleteDecl(entry.key);
     }
 }
@@ -1716,7 +1716,7 @@ pub fn analyzeRootZIRModule(self: *Module, root_scope: *Scope.ZIRModule) !void {
     // Handle explicitly deleted decls from the source code. Not to be confused
     // with when we delete decls because they are no longer referenced.
     for (deleted_decls.items()) |entry| {
-        log.debug("noticed '{}' deleted from source\n", .{entry.key.name});
+        log.debug("noticed '{s}' deleted from source\n", .{entry.key.name});
         try self.deleteDecl(entry.key);
     }
 }
@@ -1728,7 +1728,7 @@ pub fn deleteDecl(self: *Module, decl: *Decl) !void {
     // not be present in the set, and this does nothing.
     decl.scope.removeDecl(decl);
 
-    log.debug("deleting decl '{}'\n", .{decl.name});
+    log.debug("deleting decl '{s}'\n", .{decl.name});
     const name_hash = decl.fullyQualifiedNameHash();
     self.decl_table.removeAssertDiscard(name_hash);
     // Remove itself from its dependencies, because we are about to destroy the decl pointer.
@@ -1819,17 +1819,17 @@ pub fn analyzeFnBody(self: *Module, decl: *Decl, func: *Fn) !void {
     const fn_zir = func.analysis.queued;
     defer fn_zir.arena.promote(self.gpa).deinit();
     func.analysis = .{ .in_progress = {} };
-    log.debug("set {} to in_progress\n", .{decl.name});
+    log.debug("set {s} to in_progress\n", .{decl.name});
 
     try zir_sema.analyzeBody(self, &inner_block.base, fn_zir.body);
 
     const instructions = try arena.allocator.dupe(*Inst, inner_block.instructions.items);
     func.analysis = .{ .success = .{ .instructions = instructions } };
-    log.debug("set {} to success\n", .{decl.name});
+    log.debug("set {s} to success\n", .{decl.name});
 }
 
 fn markOutdatedDecl(self: *Module, decl: *Decl) !void {
-    log.debug("mark {} outdated\n", .{decl.name});
+    log.debug("mark {s} outdated\n", .{decl.name});
     try self.comp.work_queue.writeItem(.{ .analyze_decl = decl });
     if (self.failed_decls.remove(decl)) |entry| {
         entry.value.destroy(self.gpa);
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 2db15ae280..5d0e897008 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -2300,7 +2300,7 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
             !mem.isAlignedGeneric(u64, local_sym.st_value, required_alignment);
         if (need_realloc) {
             const vaddr = try self.growTextBlock(&decl.link.elf, code.len, required_alignment);
-            log.debug("growing {} from 0x{x} to 0x{x}\n", .{ decl.name, local_sym.st_value, vaddr });
+            log.debug("growing {s} from 0x{x} to 0x{x}\n", .{ decl.name, local_sym.st_value, vaddr });
             if (vaddr != local_sym.st_value) {
                 local_sym.st_value = vaddr;
 
@@ -2322,7 +2322,7 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
         const decl_name = mem.spanZ(decl.name);
         const name_str_index = try self.makeString(decl_name);
         const vaddr = try self.allocateTextBlock(&decl.link.elf, code.len, required_alignment);
-        log.debug("allocated text block for {} at 0x{x}\n", .{ decl_name, vaddr });
+        log.debug("allocated text block for {s} at 0x{x}\n", .{ decl_name, vaddr });
         errdefer self.freeTextBlock(&decl.link.elf);
 
         local_sym.* = .{
diff --git a/src/test.zig b/src/test.zig
index 6d76ae39c1..b74732d10d 100644
--- a/src/test.zig
+++ b/src/test.zig
@@ -660,7 +660,7 @@ pub const TestContext = struct {
                         }
                     }
                     if (comp.bin_file.cast(link.File.C)) |c_file| {
-                        std.debug.print("Generated C: \n===============\n{}\n\n===========\n\n", .{
+                        std.debug.print("Generated C: \n===============\n{s}\n\n===========\n\n", .{
                             c_file.main.items,
                         });
                     }
diff --git a/test/compare_output.zig b/test/compare_output.zig
index 46c475e046..9dc80f202d 100644
--- a/test/compare_output.zig
+++ b/test/compare_output.zig
@@ -453,7 +453,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
             \\    _ = args_it.skip();
             \\    while (args_it.next(allocator)) |arg_or_err| : (index += 1) {
             \\        const arg = try arg_or_err;
-            \\        try stdout.print("{}: {}\n", .{index, arg});
+            \\        try stdout.print("{}: {s}\n", .{index, arg});
             \\    }
             \\}
         ,
@@ -492,7 +492,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
             \\    _ = args_it.skip();
             \\    while (args_it.next(allocator)) |arg_or_err| : (index += 1) {
             \\        const arg = try arg_or_err;
-            \\        try stdout.print("{}: {}\n", .{index, arg});
+            \\        try stdout.print("{}: {s}\n", .{index, arg});
             \\    }
             \\}
         ,
diff --git a/test/stage1/behavior/async_fn.zig b/test/stage1/behavior/async_fn.zig
index eb9c3f5d07..16c7b14944 100644
--- a/test/stage1/behavior/async_fn.zig
+++ b/test/stage1/behavior/async_fn.zig
@@ -2,6 +2,7 @@ const std = @import("std");
 const builtin = @import("builtin");
 const expect = std.testing.expect;
 const expectEqual = std.testing.expectEqual;
+const expectEqualStrings = std.testing.expectEqualStrings;
 const expectError = std.testing.expectError;
 
 var global_x: i32 = 1;
@@ -541,7 +542,7 @@ test "pass string literal to async function" {
         fn hello(msg: []const u8) void {
             frame = @frame();
             suspend;
-            expectEqual(@as([]const u8, "hello"), msg);
+            expectEqualStrings("hello", msg);
             ok = true;
         }
     };

From 1fbe89dc2e204defc18add72efd2bba4dbe728fc Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 19:14:22 +0100
Subject: [PATCH 12/16] langref: Update langref to use {s}

---
 doc/docgen.zig      | 108 ++++++++++++++++++++++----------------------
 doc/langref.html.in |  42 ++++++++---------
 lib/std/testing.zig |   3 +-
 src/astgen.zig      |   6 +--
 src/link/MachO.zig  |   2 +-
 5 files changed, 80 insertions(+), 81 deletions(-)

diff --git a/doc/docgen.zig b/doc/docgen.zig
index e995e2f324..7e0bedbb6c 100644
--- a/doc/docgen.zig
+++ b/doc/docgen.zig
@@ -215,9 +215,9 @@ const Tokenizer = struct {
 fn parseError(tokenizer: *Tokenizer, token: Token, comptime fmt: []const u8, args: anytype) anyerror {
     const loc = tokenizer.getTokenLocation(token);
     const args_prefix = .{ tokenizer.source_file_name, loc.line + 1, loc.column + 1 };
-    print("{}:{}:{}: error: " ++ fmt ++ "\n", args_prefix ++ args);
+    print("{s}:{d}:{d}: error: " ++ fmt ++ "\n", args_prefix ++ args);
     if (loc.line_start <= loc.line_end) {
-        print("{}\n", .{tokenizer.buffer[loc.line_start..loc.line_end]});
+        print("{s}\n", .{tokenizer.buffer[loc.line_start..loc.line_end]});
         {
             var i: usize = 0;
             while (i < loc.column) : (i += 1) {
@@ -238,7 +238,7 @@ fn parseError(tokenizer: *Tokenizer, token: Token, comptime fmt: []const u8, arg
 
 fn assertToken(tokenizer: *Tokenizer, token: Token, id: Token.Id) !void {
     if (token.id != id) {
-        return parseError(tokenizer, token, "expected {}, found {}", .{ @tagName(id), @tagName(token.id) });
+        return parseError(tokenizer, token, "expected {s}, found {s}", .{ @tagName(id), @tagName(token.id) });
     }
 }
 
@@ -374,7 +374,7 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                                     return parseError(
                                         tokenizer,
                                         bracket_tok,
-                                        "unrecognized header_open param: {}",
+                                        "unrecognized header_open param: {s}",
                                         .{param},
                                     );
                                 }
@@ -394,7 +394,7 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                         },
                     });
                     if (try urls.fetchPut(urlized, tag_token)) |entry| {
-                        parseError(tokenizer, tag_token, "duplicate header url: #{}", .{urlized}) catch {};
+                        parseError(tokenizer, tag_token, "duplicate header url: #{s}", .{urlized}) catch {};
                         parseError(tokenizer, entry.value, "other tag here", .{}) catch {};
                         return error.ParseError;
                     }
@@ -411,7 +411,7 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                     }
                     last_columns = columns;
                     try toc.writeByteNTimes(' ', 4 + header_stack_size * 4);
-                    try toc.print("<li><a id=\"toc-{}\" href=\"#{}\">{}</a>", .{ urlized, urlized, content });
+                    try toc.print("<li><a id=\"toc-{s}\" href=\"#{s}\">{s}</a>", .{ urlized, urlized, content });
                 } else if (mem.eql(u8, tag_name, "header_close")) {
                     if (header_stack_size == 0) {
                         return parseError(tokenizer, tag_token, "unbalanced close header", .{});
@@ -515,7 +515,7 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                         code_kind_id = Code.Id{ .Obj = null };
                         is_inline = true;
                     } else {
-                        return parseError(tokenizer, code_kind_tok, "unrecognized code kind: {}", .{code_kind_str});
+                        return parseError(tokenizer, code_kind_tok, "unrecognized code kind: {s}", .{code_kind_str});
                     }
 
                     var mode: builtin.Mode = .Debug;
@@ -559,7 +559,7 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                             return parseError(
                                 tokenizer,
                                 end_code_tag,
-                                "invalid token inside code_begin: {}",
+                                "invalid token inside code_begin: {s}",
                                 .{end_tag_name},
                             );
                         }
@@ -590,14 +590,14 @@ fn genToc(allocator: *mem.Allocator, tokenizer: *Tokenizer) !Toc {
                         return parseError(
                             tokenizer,
                             end_syntax_tag,
-                            "invalid token inside syntax: {}",
+                            "invalid token inside syntax: {s}",
                             .{end_tag_name},
                         );
                     }
                     _ = try eatToken(tokenizer, Token.Id.BracketClose);
                     try nodes.append(Node{ .Syntax = content_tok });
                 } else {
-                    return parseError(tokenizer, tag_token, "unrecognized tag name: {}", .{tag_name});
+                    return parseError(tokenizer, tag_token, "unrecognized tag name: {s}", .{tag_name});
                 }
             },
             else => return parseError(tokenizer, token, "invalid token", .{}),
@@ -744,7 +744,7 @@ fn termColor(allocator: *mem.Allocator, input: []const u8) ![]u8 {
                         try out.writeAll("</span>");
                     }
                     if (first_number != 0 or second_number != 0) {
-                        try out.print("<span class=\"t{}_{}\">", .{ first_number, second_number });
+                        try out.print("<span class=\"t{d}_{d}\">", .{ first_number, second_number });
                         open_span_count += 1;
                     }
                 },
@@ -1004,9 +1004,9 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
             },
             .Link => |info| {
                 if (!toc.urls.contains(info.url)) {
-                    return parseError(tokenizer, info.token, "url not found: {}", .{info.url});
+                    return parseError(tokenizer, info.token, "url not found: {s}", .{info.url});
                 }
-                try out.print("<a href=\"#{}\">{}</a>", .{ info.url, info.name });
+                try out.print("<a href=\"#{s}\">{s}</a>", .{ info.url, info.name });
             },
             .Nav => {
                 try out.writeAll(toc.toc);
@@ -1018,7 +1018,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
             },
             .HeaderOpen => |info| {
                 try out.print(
-                    "<h{} id=\"{}\"><a href=\"#toc-{}\">{}</a> <a class=\"hdr\" href=\"#{}\">§</a></h{}>\n",
+                    "<h{d} id=\"{s}\"><a href=\"#toc-{s}\">{s}</a> <a class=\"hdr\" href=\"#{s}\">§</a></h{d}>\n",
                     .{ info.n, info.url, info.url, info.name, info.url, info.n },
                 );
             },
@@ -1027,9 +1027,9 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                 for (items) |item| {
                     const url = try urlize(allocator, item.name);
                     if (!toc.urls.contains(url)) {
-                        return parseError(tokenizer, item.token, "url not found: {}", .{url});
+                        return parseError(tokenizer, item.token, "url not found: {s}", .{url});
                     }
-                    try out.print("<li><a href=\"#{}\">{}</a></li>\n", .{ url, item.name });
+                    try out.print("<li><a href=\"#{s}\">{s}</a></li>\n", .{ url, item.name });
                 }
                 try out.writeAll("</ul>\n");
             },
@@ -1043,12 +1043,12 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                 const raw_source = tokenizer.buffer[code.source_token.start..code.source_token.end];
                 const trimmed_raw_source = mem.trim(u8, raw_source, " \n");
                 if (!code.is_inline) {
-                    try out.print("<p class=\"file\">{}.zig</p>", .{code.name});
+                    try out.print("<p class=\"file\">{s}.zig</p>", .{code.name});
                 }
                 try out.writeAll("<pre>");
                 try tokenizeAndPrint(tokenizer, out, code.source_token);
                 try out.writeAll("</pre>");
-                const name_plus_ext = try std.fmt.allocPrint(allocator, "{}.zig", .{code.name});
+                const name_plus_ext = try std.fmt.allocPrint(allocator, "{s}.zig", .{code.name});
                 const tmp_source_file_name = try fs.path.join(
                     allocator,
                     &[_][]const u8{ tmp_dir_name, name_plus_ext },
@@ -1057,7 +1057,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
 
                 switch (code.id) {
                     Code.Id.Exe => |expected_outcome| code_block: {
-                        const name_plus_bin_ext = try std.fmt.allocPrint(allocator, "{}{}", .{ code.name, exe_ext });
+                        const name_plus_bin_ext = try std.fmt.allocPrint(allocator, "{s}{s}", .{ code.name, exe_ext });
                         var build_args = std.ArrayList([]const u8).init(allocator);
                         defer build_args.deinit();
                         try build_args.appendSlice(&[_][]const u8{
@@ -1066,7 +1066,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             "--color",        "on",
                             "--enable-cache", tmp_source_file_name,
                         });
-                        try out.print("<pre><code class=\"shell\">$ zig build-exe {}.zig", .{code.name});
+                        try out.print("<pre><code class=\"shell\">$ zig build-exe {s}.zig", .{code.name});
                         switch (code.mode) {
                             .Debug => {},
                             else => {
@@ -1075,7 +1075,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             },
                         }
                         for (code.link_objects) |link_object| {
-                            const name_with_ext = try std.fmt.allocPrint(allocator, "{}{}", .{ link_object, obj_ext });
+                            const name_with_ext = try std.fmt.allocPrint(allocator, "{s}{s}", .{ link_object, obj_ext });
                             const full_path_object = try fs.path.join(
                                 allocator,
                                 &[_][]const u8{ tmp_dir_name, name_with_ext },
@@ -1093,7 +1093,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         if (code.target_str) |triple| {
                             try build_args.appendSlice(&[_][]const u8{ "-target", triple });
                             if (!code.is_inline) {
-                                try out.print(" -target {}", .{triple});
+                                try out.print(" -target {s}", .{triple});
                             }
                         }
                         if (expected_outcome == .BuildFail) {
@@ -1106,20 +1106,20 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             switch (result.term) {
                                 .Exited => |exit_code| {
                                     if (exit_code == 0) {
-                                        print("{}\nThe following command incorrectly succeeded:\n", .{result.stderr});
+                                        print("{s}\nThe following command incorrectly succeeded:\n", .{result.stderr});
                                         dumpArgs(build_args.items);
                                         return parseError(tokenizer, code.source_token, "example incorrectly compiled", .{});
                                     }
                                 },
                                 else => {
-                                    print("{}\nThe following command crashed:\n", .{result.stderr});
+                                    print("{s}\nThe following command crashed:\n", .{result.stderr});
                                     dumpArgs(build_args.items);
                                     return parseError(tokenizer, code.source_token, "example compile crashed", .{});
                                 },
                             }
                             const escaped_stderr = try escapeHtml(allocator, result.stderr);
                             const colored_stderr = try termColor(allocator, escaped_stderr);
-                            try out.print("\n{}</code></pre>\n", .{colored_stderr});
+                            try out.print("\n{s}</code></pre>\n", .{colored_stderr});
                             break :code_block;
                         }
                         const exec_result = exec(allocator, &env_map, build_args.items) catch
@@ -1138,7 +1138,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         }
 
                         const path_to_exe_dir = mem.trim(u8, exec_result.stdout, " \r\n");
-                        const path_to_exe_basename = try std.fmt.allocPrint(allocator, "{}{}", .{
+                        const path_to_exe_basename = try std.fmt.allocPrint(allocator, "{s}{s}", .{
                             code.name,
                             target.exeFileExt(),
                         });
@@ -1160,7 +1160,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             switch (result.term) {
                                 .Exited => |exit_code| {
                                     if (exit_code == 0) {
-                                        print("{}\nThe following command incorrectly succeeded:\n", .{result.stderr});
+                                        print("{s}\nThe following command incorrectly succeeded:\n", .{result.stderr});
                                         dumpArgs(run_args);
                                         return parseError(tokenizer, code.source_token, "example incorrectly compiled", .{});
                                     }
@@ -1179,7 +1179,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         const colored_stderr = try termColor(allocator, escaped_stderr);
                         const colored_stdout = try termColor(allocator, escaped_stdout);
 
-                        try out.print("\n$ ./{}\n{}{}", .{ code.name, colored_stdout, colored_stderr });
+                        try out.print("\n$ ./{s}\n{s}{s}", .{ code.name, colored_stdout, colored_stderr });
                         if (exited_with_signal) {
                             try out.print("(process terminated by signal)", .{});
                         }
@@ -1190,7 +1190,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         defer test_args.deinit();
 
                         try test_args.appendSlice(&[_][]const u8{ zig_exe, "test", tmp_source_file_name });
-                        try out.print("<pre><code class=\"shell\">$ zig test {}.zig", .{code.name});
+                        try out.print("<pre><code class=\"shell\">$ zig test {s}.zig", .{code.name});
                         switch (code.mode) {
                             .Debug => {},
                             else => {
@@ -1204,12 +1204,12 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         }
                         if (code.target_str) |triple| {
                             try test_args.appendSlice(&[_][]const u8{ "-target", triple });
-                            try out.print(" -target {}", .{triple});
+                            try out.print(" -target {s}", .{triple});
                         }
                         const result = exec(allocator, &env_map, test_args.items) catch return parseError(tokenizer, code.source_token, "test failed", .{});
                         const escaped_stderr = try escapeHtml(allocator, result.stderr);
                         const escaped_stdout = try escapeHtml(allocator, result.stdout);
-                        try out.print("\n{}{}</code></pre>\n", .{ escaped_stderr, escaped_stdout });
+                        try out.print("\n{s}{s}</code></pre>\n", .{ escaped_stderr, escaped_stdout });
                     },
                     Code.Id.TestError => |error_match| {
                         var test_args = std.ArrayList([]const u8).init(allocator);
@@ -1222,7 +1222,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             "on",
                             tmp_source_file_name,
                         });
-                        try out.print("<pre><code class=\"shell\">$ zig test {}.zig", .{code.name});
+                        try out.print("<pre><code class=\"shell\">$ zig test {s}.zig", .{code.name});
                         switch (code.mode) {
                             .Debug => {},
                             else => {
@@ -1239,24 +1239,24 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         switch (result.term) {
                             .Exited => |exit_code| {
                                 if (exit_code == 0) {
-                                    print("{}\nThe following command incorrectly succeeded:\n", .{result.stderr});
+                                    print("{s}\nThe following command incorrectly succeeded:\n", .{result.stderr});
                                     dumpArgs(test_args.items);
                                     return parseError(tokenizer, code.source_token, "example incorrectly compiled", .{});
                                 }
                             },
                             else => {
-                                print("{}\nThe following command crashed:\n", .{result.stderr});
+                                print("{s}\nThe following command crashed:\n", .{result.stderr});
                                 dumpArgs(test_args.items);
                                 return parseError(tokenizer, code.source_token, "example compile crashed", .{});
                             },
                         }
                         if (mem.indexOf(u8, result.stderr, error_match) == null) {
-                            print("{}\nExpected to find '{}' in stderr\n", .{ result.stderr, error_match });
+                            print("{s}\nExpected to find '{s}' in stderr\n", .{ result.stderr, error_match });
                             return parseError(tokenizer, code.source_token, "example did not have expected compile error", .{});
                         }
                         const escaped_stderr = try escapeHtml(allocator, result.stderr);
                         const colored_stderr = try termColor(allocator, escaped_stderr);
-                        try out.print("\n{}</code></pre>\n", .{colored_stderr});
+                        try out.print("\n{s}</code></pre>\n", .{colored_stderr});
                     },
 
                     Code.Id.TestSafety => |error_match| {
@@ -1294,31 +1294,31 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         switch (result.term) {
                             .Exited => |exit_code| {
                                 if (exit_code == 0) {
-                                    print("{}\nThe following command incorrectly succeeded:\n", .{result.stderr});
+                                    print("{s}\nThe following command incorrectly succeeded:\n", .{result.stderr});
                                     dumpArgs(test_args.items);
                                     return parseError(tokenizer, code.source_token, "example test incorrectly succeeded", .{});
                                 }
                             },
                             else => {
-                                print("{}\nThe following command crashed:\n", .{result.stderr});
+                                print("{s}\nThe following command crashed:\n", .{result.stderr});
                                 dumpArgs(test_args.items);
                                 return parseError(tokenizer, code.source_token, "example compile crashed", .{});
                             },
                         }
                         if (mem.indexOf(u8, result.stderr, error_match) == null) {
-                            print("{}\nExpected to find '{}' in stderr\n", .{ result.stderr, error_match });
+                            print("{s}\nExpected to find '{s}' in stderr\n", .{ result.stderr, error_match });
                             return parseError(tokenizer, code.source_token, "example did not have expected runtime safety error message", .{});
                         }
                         const escaped_stderr = try escapeHtml(allocator, result.stderr);
                         const colored_stderr = try termColor(allocator, escaped_stderr);
-                        try out.print("<pre><code class=\"shell\">$ zig test {}.zig{}\n{}</code></pre>\n", .{
+                        try out.print("<pre><code class=\"shell\">$ zig test {s}.zig{s}\n{s}</code></pre>\n", .{
                             code.name,
                             mode_arg,
                             colored_stderr,
                         });
                     },
                     Code.Id.Obj => |maybe_error_match| {
-                        const name_plus_obj_ext = try std.fmt.allocPrint(allocator, "{}{}", .{ code.name, obj_ext });
+                        const name_plus_obj_ext = try std.fmt.allocPrint(allocator, "{s}{s}", .{ code.name, obj_ext });
                         const tmp_obj_file_name = try fs.path.join(
                             allocator,
                             &[_][]const u8{ tmp_dir_name, name_plus_obj_ext },
@@ -1326,7 +1326,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         var build_args = std.ArrayList([]const u8).init(allocator);
                         defer build_args.deinit();
 
-                        const name_plus_h_ext = try std.fmt.allocPrint(allocator, "{}.h", .{code.name});
+                        const name_plus_h_ext = try std.fmt.allocPrint(allocator, "{s}.h", .{code.name});
                         const output_h_file_name = try fs.path.join(
                             allocator,
                             &[_][]const u8{ tmp_dir_name, name_plus_h_ext },
@@ -1345,7 +1345,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             }),
                         });
                         if (!code.is_inline) {
-                            try out.print("<pre><code class=\"shell\">$ zig build-obj {}.zig", .{code.name});
+                            try out.print("<pre><code class=\"shell\">$ zig build-obj {s}.zig", .{code.name});
                         }
 
                         switch (code.mode) {
@@ -1360,7 +1360,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
 
                         if (code.target_str) |triple| {
                             try build_args.appendSlice(&[_][]const u8{ "-target", triple });
-                            try out.print(" -target {}", .{triple});
+                            try out.print(" -target {s}", .{triple});
                         }
 
                         if (maybe_error_match) |error_match| {
@@ -1373,24 +1373,24 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                             switch (result.term) {
                                 .Exited => |exit_code| {
                                     if (exit_code == 0) {
-                                        print("{}\nThe following command incorrectly succeeded:\n", .{result.stderr});
+                                        print("{s}\nThe following command incorrectly succeeded:\n", .{result.stderr});
                                         dumpArgs(build_args.items);
                                         return parseError(tokenizer, code.source_token, "example build incorrectly succeeded", .{});
                                     }
                                 },
                                 else => {
-                                    print("{}\nThe following command crashed:\n", .{result.stderr});
+                                    print("{s}\nThe following command crashed:\n", .{result.stderr});
                                     dumpArgs(build_args.items);
                                     return parseError(tokenizer, code.source_token, "example compile crashed", .{});
                                 },
                             }
                             if (mem.indexOf(u8, result.stderr, error_match) == null) {
-                                print("{}\nExpected to find '{}' in stderr\n", .{ result.stderr, error_match });
+                                print("{s}\nExpected to find '{s}' in stderr\n", .{ result.stderr, error_match });
                                 return parseError(tokenizer, code.source_token, "example did not have expected compile error message", .{});
                             }
                             const escaped_stderr = try escapeHtml(allocator, result.stderr);
                             const colored_stderr = try termColor(allocator, escaped_stderr);
-                            try out.print("\n{}", .{colored_stderr});
+                            try out.print("\n{s}", .{colored_stderr});
                         } else {
                             _ = exec(allocator, &env_map, build_args.items) catch return parseError(tokenizer, code.source_token, "example failed to compile", .{});
                         }
@@ -1416,7 +1416,7 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                                 tmp_dir_name, fs.path.sep_str, bin_basename,
                             }),
                         });
-                        try out.print("<pre><code class=\"shell\">$ zig build-lib {}.zig", .{code.name});
+                        try out.print("<pre><code class=\"shell\">$ zig build-lib {s}.zig", .{code.name});
                         switch (code.mode) {
                             .Debug => {},
                             else => {
@@ -1426,12 +1426,12 @@ fn genHtml(allocator: *mem.Allocator, tokenizer: *Tokenizer, toc: *Toc, out: any
                         }
                         if (code.target_str) |triple| {
                             try test_args.appendSlice(&[_][]const u8{ "-target", triple });
-                            try out.print(" -target {}", .{triple});
+                            try out.print(" -target {s}", .{triple});
                         }
                         const result = exec(allocator, &env_map, test_args.items) catch return parseError(tokenizer, code.source_token, "test failed", .{});
                         const escaped_stderr = try escapeHtml(allocator, result.stderr);
                         const escaped_stdout = try escapeHtml(allocator, result.stdout);
-                        try out.print("\n{}{}</code></pre>\n", .{ escaped_stderr, escaped_stdout });
+                        try out.print("\n{s}{s}</code></pre>\n", .{ escaped_stderr, escaped_stdout });
                     },
                 }
                 print("OK\n", .{});
@@ -1450,13 +1450,13 @@ fn exec(allocator: *mem.Allocator, env_map: *std.BufMap, args: []const []const u
     switch (result.term) {
         .Exited => |exit_code| {
             if (exit_code != 0) {
-                print("{}\nThe following command exited with code {}:\n", .{ result.stderr, exit_code });
+                print("{s}\nThe following command exited with code {}:\n", .{ result.stderr, exit_code });
                 dumpArgs(args);
                 return error.ChildExitError;
             }
         },
         else => {
-            print("{}\nThe following command crashed:\n", .{result.stderr});
+            print("{s}\nThe following command crashed:\n", .{result.stderr});
             dumpArgs(args);
             return error.ChildCrashed;
         },
@@ -1471,7 +1471,7 @@ fn getBuiltinCode(allocator: *mem.Allocator, env_map: *std.BufMap, zig_exe: []co
 
 fn dumpArgs(args: []const []const u8) void {
     for (args) |arg|
-        print("{} ", .{arg})
+        print("{s} ", .{arg})
     else
         print("\n", .{});
 }
diff --git a/doc/langref.html.in b/doc/langref.html.in
index 7c8d1c6662..9d89e894ad 100644
--- a/doc/langref.html.in
+++ b/doc/langref.html.in
@@ -236,7 +236,7 @@ const std = @import("std");
 
 pub fn main() !void {
     const stdout = std.io.getStdOut().writer();
-    try stdout.print("Hello, {}!\n", .{"world"});
+    try stdout.print("Hello, {s}!\n", .{"world"});
 }
       {#code_end#}
       <p>
@@ -308,7 +308,7 @@ pub fn main() !void {
         multiple arguments passed to a function, they are separated by commas <code>,</code>.
       </p>
       <p>
-        The two arguments passed to the <code>stdout.print()</code> function, <code>"Hello, {}!\n"</code>
+        The two arguments passed to the <code>stdout.print()</code> function, <code>"Hello, {s}!\n"</code>
         and <code>.{"world"}</code>, are evaluated at {#link|compile-time|comptime#}. The code sample is
         purposely written to show how to perform {#link|string|String Literals and Character Literals#}
         substitution in the <code>print</code> function. The curly-braces inside of the first argument
@@ -435,7 +435,7 @@ pub fn main() void {
     var optional_value: ?[]const u8 = null;
     assert(optional_value == null);
 
-    print("\noptional 1\ntype: {}\nvalue: {}\n", .{
+    print("\noptional 1\ntype: {s}\nvalue: {s}\n", .{
         @typeName(@TypeOf(optional_value)),
         optional_value,
     });
@@ -443,7 +443,7 @@ pub fn main() void {
     optional_value = "hi";
     assert(optional_value != null);
 
-    print("\noptional 2\ntype: {}\nvalue: {}\n", .{
+    print("\noptional 2\ntype: {s}\nvalue: {s}\n", .{
         @typeName(@TypeOf(optional_value)),
         optional_value,
     });
@@ -451,14 +451,14 @@ pub fn main() void {
     // error union
     var number_or_error: anyerror!i32 = error.ArgNotFound;
 
-    print("\nerror union 1\ntype: {}\nvalue: {}\n", .{
+    print("\nerror union 1\ntype: {s}\nvalue: {}\n", .{
         @typeName(@TypeOf(number_or_error)),
         number_or_error,
     });
 
     number_or_error = 1234;
 
-    print("\nerror union 2\ntype: {}\nvalue: {}\n", .{
+    print("\nerror union 2\ntype: {s}\nvalue: {}\n", .{
         @typeName(@TypeOf(number_or_error)),
         number_or_error,
     });
@@ -2339,7 +2339,7 @@ test "using slices for strings" {
     // You can use slice syntax on an array to convert an array into a slice.
     const all_together_slice = all_together[0..];
     // String concatenation example.
-    const hello_world = try fmt.bufPrint(all_together_slice, "{} {}", .{ hello, world });
+    const hello_world = try fmt.bufPrint(all_together_slice, "{s} {s}", .{ hello, world });
 
     // Generally, you can use UTF-8 and not worry about whether something is a
     // string. If you don't need to deal with individual characters, no need
@@ -2772,9 +2772,9 @@ const std = @import("std");
 
 pub fn main() void {
     const Foo = struct {};
-    std.debug.print("variable: {}\n", .{@typeName(Foo)});
-    std.debug.print("anonymous: {}\n", .{@typeName(struct {})});
-    std.debug.print("function: {}\n", .{@typeName(List(i32))});
+    std.debug.print("variable: {s}\n", .{@typeName(Foo)});
+    std.debug.print("anonymous: {s}\n", .{@typeName(struct {})});
+    std.debug.print("function: {s}\n", .{@typeName(List(i32))});
 }
 
 fn List(comptime T: type) type {
@@ -6110,7 +6110,7 @@ const a_number: i32 = 1234;
 const a_string = "foobar";
 
 pub fn main() void {
-    print("here is a string: '{}' here is a number: {}\n", .{a_string, a_number});
+    print("here is a string: '{s}' here is a number: {}\n", .{a_string, a_number});
 }
       {#code_end#}
 
@@ -6230,7 +6230,7 @@ const a_number: i32 = 1234;
 const a_string = "foobar";
 
 test "printf too many arguments" {
-    print("here is a string: '{}' here is a number: {}\n", .{
+    print("here is a string: '{s}' here is a number: {}\n", .{
         a_string,
         a_number,
         a_number,
@@ -6249,7 +6249,7 @@ const print = @import("std").debug.print;
 
 const a_number: i32 = 1234;
 const a_string = "foobar";
-const fmt = "here is a string: '{}' here is a number: {}\n";
+const fmt = "here is a string: '{s}' here is a number: {}\n";
 
 pub fn main() void {
     print(fmt, .{a_string, a_number});
@@ -6720,8 +6720,8 @@ fn amain() !void {
     const download_text = try await download_frame;
     defer allocator.free(download_text);
 
-    std.debug.print("download_text: {}\n", .{download_text});
-    std.debug.print("file_text: {}\n", .{file_text});
+    std.debug.print("download_text: {s}\n", .{download_text});
+    std.debug.print("file_text: {s}\n", .{file_text});
 }
 
 var global_download_frame: anyframe = undefined;
@@ -6790,8 +6790,8 @@ fn amain() !void {
     const download_text = try await download_frame;
     defer allocator.free(download_text);
 
-    std.debug.print("download_text: {}\n", .{download_text});
-    std.debug.print("file_text: {}\n", .{file_text});
+    std.debug.print("download_text: {s}\n", .{download_text});
+    std.debug.print("file_text: {s}\n", .{file_text});
 }
 
 fn fetchUrl(allocator: *Allocator, url: []const u8) ![]u8 {
@@ -8848,7 +8848,7 @@ pub fn main() !void {
     var byte: u8 = 255;
 
     byte = if (math.add(u8, byte, 1)) |result| result else |err| {
-        print("unable to add one: {}\n", .{@errorName(err)});
+        print("unable to add one: {s}\n", .{@errorName(err)});
         return err;
     };
 
@@ -9078,7 +9078,7 @@ pub fn main() void {
     if (result) |number| {
         print("got number: {}\n", .{number});
     } else |err| {
-        print("got error: {}\n", .{@errorName(err)});
+        print("got error: {s}\n", .{@errorName(err)});
     }
 }
 
@@ -9135,7 +9135,7 @@ const Foo = enum {
 pub fn main() void {
     var a: u2 = 3;
     var b = @intToEnum(Foo, a);
-    std.debug.print("value: {}\n", .{@tagName(b)});
+    std.debug.print("value: {s}\n", .{@tagName(b)});
 }
       {#code_end#}
       {#header_close#}
@@ -10025,7 +10025,7 @@ pub fn main() !void {
     defer std.process.argsFree(gpa, args);
 
     for (args) |arg, i| {
-        std.debug.print("{}: {}\n", .{ i, arg });
+        std.debug.print("{}: {s}\n", .{ i, arg });
     }
 }
       {#code_end#}
diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index d1f025c929..80cc7f930d 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -29,8 +29,7 @@ pub var zig_exe_path: []const u8 = undefined;
 /// and then aborts when actual_error_union is not expected_error.
 pub fn expectError(expected_error: anyerror, actual_error_union: anytype) void {
     if (actual_error_union) |actual_payload| {
-        // std.debug.panic("expected error.{s}, found {}", .{ @errorName(expected_error), actual_payload });
-        std.debug.panic("expected error.{s}, found", .{@errorName(expected_error)});
+        std.debug.panic("expected error.{s}, found {}", .{ @errorName(expected_error), actual_payload });
     } else |actual_error| {
         if (expected_error != actual_error) {
             std.debug.panic("expected error.{s}, found error.{s}", .{
diff --git a/src/astgen.zig b/src/astgen.zig
index b4e1760368..b3cb648dcb 100644
--- a/src/astgen.zig
+++ b/src/astgen.zig
@@ -560,14 +560,14 @@ fn varDecl(
             .local_val => {
                 const local_val = s.cast(Scope.LocalVal).?;
                 if (mem.eql(u8, local_val.name, ident_name)) {
-                    return mod.fail(scope, name_src, "redefinition of '{}'", .{ident_name});
+                    return mod.fail(scope, name_src, "redefinition of '{s}'", .{ident_name});
                 }
                 s = local_val.parent;
             },
             .local_ptr => {
                 const local_ptr = s.cast(Scope.LocalPtr).?;
                 if (mem.eql(u8, local_ptr.name, ident_name)) {
-                    return mod.fail(scope, name_src, "redefinition of '{}'", .{ident_name});
+                    return mod.fail(scope, name_src, "redefinition of '{s}'", .{ident_name});
                 }
                 s = local_ptr.parent;
             },
@@ -578,7 +578,7 @@ fn varDecl(
 
     // Namespace vars shadowing detection
     if (mod.lookupDeclName(scope, ident_name)) |_| {
-        return mod.fail(scope, name_src, "redefinition of '{}'", .{ident_name});
+        return mod.fail(scope, name_src, "redefinition of '{s}'", .{ident_name});
     }
     const init_node = node.getInitNode() orelse
         return mod.fail(scope, name_src, "variables must be initialized", .{});
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
index d4a61c8149..3f8544a4e8 100644
--- a/src/link/MachO.zig
+++ b/src/link/MachO.zig
@@ -620,7 +620,7 @@ fn linkWithLLD(self: *MachO, comp: *Compilation) !void {
                 try argv.append(cur_vers);
             }
 
-            const dylib_install_name = try std.fmt.allocPrint(arena, "@rpath/{}", .{self.base.options.emit.?.sub_path});
+            const dylib_install_name = try std.fmt.allocPrint(arena, "@rpath/{s}", .{self.base.options.emit.?.sub_path});
             try argv.append("-install_name");
             try argv.append(dylib_install_name);
         }

From 04f37dcd8e9c32d7ce8712939fb9c8dfa6cc6bbe Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Thu, 26 Nov 2020 22:20:44 +0100
Subject: [PATCH 13/16] stage2: Use {z} instead of {s} in generated Zig code

---
 src/Compilation.zig | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/Compilation.zig b/src/Compilation.zig
index 3a9c1ea993..c688cf7980 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -2653,15 +2653,15 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\pub const arch = Target.current.cpu.arch;
         \\/// Deprecated
         \\pub const endian = Target.current.cpu.arch.endian();
-        \\pub const output_mode = OutputMode.{s};
-        \\pub const link_mode = LinkMode.{s};
+        \\pub const output_mode = OutputMode.{z};
+        \\pub const link_mode = LinkMode.{z};
         \\pub const is_test = {};
         \\pub const single_threaded = {};
-        \\pub const abi = Abi.{s};
+        \\pub const abi = Abi.{z};
         \\pub const cpu: Cpu = Cpu{{
-        \\    .arch = .{s},
-        \\    .model = &Target.{s}.cpu.{s},
-        \\    .features = Target.{s}.featureSet(&[_]Target.{s}.Feature{{
+        \\    .arch = .{z},
+        \\    .model = &Target.{z}.cpu.{z},
+        \\    .features = Target.{z}.featureSet(&[_]Target.{z}.Feature{{
         \\
     , .{
         @tagName(comp.bin_file.options.output_mode),
@@ -2692,7 +2692,7 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\    }}),
         \\}};
         \\pub const os = Os{{
-        \\    .tag = .{s},
+        \\    .tag = .{z},
         \\    .version_range = .{{
     ,
         .{@tagName(target.os.tag)},
@@ -2778,8 +2778,8 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         (comp.bin_file.options.skip_linker_dependencies and comp.bin_file.options.parent_compilation_link_libc);
 
     try buffer.writer().print(
-        \\pub const object_format = ObjectFormat.{s};
-        \\pub const mode = Mode.{s};
+        \\pub const object_format = ObjectFormat.{z};
+        \\pub const mode = Mode.{z};
         \\pub const link_libc = {};
         \\pub const link_libcpp = {};
         \\pub const have_error_return_tracing = {};
@@ -2787,7 +2787,7 @@ pub fn generateBuiltinZigSource(comp: *Compilation, allocator: *Allocator) ![]u8
         \\pub const position_independent_code = {};
         \\pub const position_independent_executable = {};
         \\pub const strip_debug_info = {};
-        \\pub const code_model = CodeModel.{s};
+        \\pub const code_model = CodeModel.{z};
         \\
     , .{
         @tagName(comp.bin_file.options.object_format),

From 608a73efb12df43fbc136c4439558f87a063dc31 Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Wed, 2 Dec 2020 20:02:51 +0100
Subject: [PATCH 14/16] Decrement max_depth when printing slice elements

---
 lib/std/fmt.zig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig
index 54d96168e2..bc9ac92283 100644
--- a/lib/std/fmt.zig
+++ b/lib/std/fmt.zig
@@ -537,7 +537,7 @@ pub fn formatType(
                 }
                 try writer.writeAll("{ ");
                 for (value) |elem, i| {
-                    try formatType(elem, fmt, options, writer, max_depth);
+                    try formatType(elem, fmt, options, writer, max_depth - 1);
                     if (i != value.len - 1) {
                         try writer.writeAll(", ");
                     }
@@ -580,7 +580,7 @@ pub fn formatType(
         .Type => return formatBuf(@typeName(value), options, writer),
         .EnumLiteral => {
             const buffer = [_]u8{'.'} ++ @tagName(value);
-            return formatType(buffer, fmt, options, writer, max_depth);
+            return formatBuf(buffer, options, writer);
         },
         .Null => return formatBuf("null", options, writer),
         else => @compileError("Unable to format type '" ++ @typeName(T) ++ "'"),

From 5b981b1be7b387a3f51d60b8642064e6642b956c Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Sat, 2 Jan 2021 12:29:37 +0100
Subject: [PATCH 15/16] Remove some unwanted changes

Leftovers after a long rebase.
---
 build.zig                         | 189 ------------------
 lib/std/array_list_sentineled.zig | 229 ----------------------
 lib/std/progress.zig              | 310 ------------------------------
 src/codegen/c.zig                 |   5 +-
 src/codegen/llvm.zig              | 125 ------------
 src/link/C.zig                    |   3 -
 src/llvm_backend.zig              |   2 +-
 7 files changed, 3 insertions(+), 860 deletions(-)
 delete mode 100644 lib/std/array_list_sentineled.zig
 delete mode 100644 lib/std/progress.zig
 delete mode 100644 src/codegen/llvm.zig

diff --git a/build.zig b/build.zig
index ab230d8f46..2b0685d19e 100644
--- a/build.zig
+++ b/build.zig
@@ -359,195 +359,6 @@ pub fn build(b: *Builder) !void {
     test_step.dependOn(docs_step);
 }
 
-fn dependOnLib(b: *Builder, lib_exe_obj: anytype, dep: LibraryDep) void {
-    for (dep.libdirs.items) |lib_dir| {
-        lib_exe_obj.addLibPath(lib_dir);
-    }
-    const lib_dir = fs.path.join(
-        b.allocator,
-        &[_][]const u8{ dep.prefix, "lib" },
-    ) catch unreachable;
-    for (dep.system_libs.items) |lib| {
-        const static_bare_name = if (mem.eql(u8, lib, "curses"))
-            @as([]const u8, "libncurses.a")
-        else
-            b.fmt("lib{s}.a", .{lib});
-        const static_lib_name = fs.path.join(
-            b.allocator,
-            &[_][]const u8{ lib_dir, static_bare_name },
-        ) catch unreachable;
-        const have_static = fileExists(static_lib_name) catch unreachable;
-        if (have_static) {
-            lib_exe_obj.addObjectFile(static_lib_name);
-        } else {
-            lib_exe_obj.linkSystemLibrary(lib);
-        }
-    }
-    for (dep.libs.items) |lib| {
-        lib_exe_obj.addObjectFile(lib);
-    }
-    for (dep.includes.items) |include_path| {
-        lib_exe_obj.addIncludeDir(include_path);
-    }
-}
-
-fn fileExists(filename: []const u8) !bool {
-    fs.cwd().access(filename, .{}) catch |err| switch (err) {
-        error.FileNotFound => return false,
-        else => return err,
-    };
-    return true;
-}
-
-fn addCppLib(b: *Builder, lib_exe_obj: anytype, cmake_binary_dir: []const u8, lib_name: []const u8) void {
-    lib_exe_obj.addObjectFile(fs.path.join(b.allocator, &[_][]const u8{
-        cmake_binary_dir,
-        "zigcpp",
-        b.fmt("{s}{s}{s}", .{ lib_exe_obj.target.libPrefix(), lib_name, lib_exe_obj.target.staticLibSuffix() }),
-    }) catch unreachable);
-}
-
-const LibraryDep = struct {
-    prefix: []const u8,
-    libdirs: ArrayList([]const u8),
-    libs: ArrayList([]const u8),
-    system_libs: ArrayList([]const u8),
-    includes: ArrayList([]const u8),
-};
-
-fn findLLVM(b: *Builder, llvm_config_exe: []const u8) !LibraryDep {
-    const shared_mode = try b.exec(&[_][]const u8{ llvm_config_exe, "--shared-mode" });
-    const is_static = mem.startsWith(u8, shared_mode, "static");
-    const libs_output = if (is_static)
-        try b.exec(&[_][]const u8{
-            llvm_config_exe,
-            "--libfiles",
-            "--system-libs",
-        })
-    else
-        try b.exec(&[_][]const u8{
-            llvm_config_exe,
-            "--libs",
-        });
-    const includes_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--includedir" });
-    const libdir_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--libdir" });
-    const prefix_output = try b.exec(&[_][]const u8{ llvm_config_exe, "--prefix" });
-
-    var result = LibraryDep{
-        .prefix = mem.tokenize(prefix_output, " \r\n").next().?,
-        .libs = ArrayList([]const u8).init(b.allocator),
-        .system_libs = ArrayList([]const u8).init(b.allocator),
-        .includes = ArrayList([]const u8).init(b.allocator),
-        .libdirs = ArrayList([]const u8).init(b.allocator),
-    };
-    {
-        var it = mem.tokenize(libs_output, " \r\n");
-        while (it.next()) |lib_arg| {
-            if (mem.startsWith(u8, lib_arg, "-l")) {
-                try result.system_libs.append(lib_arg[2..]);
-            } else {
-                if (fs.path.isAbsolute(lib_arg)) {
-                    try result.libs.append(lib_arg);
-                } else {
-                    var lib_arg_copy = lib_arg;
-                    if (mem.endsWith(u8, lib_arg, ".lib")) {
-                        lib_arg_copy = lib_arg[0 .. lib_arg.len - 4];
-                    }
-                    try result.system_libs.append(lib_arg_copy);
-                }
-            }
-        }
-    }
-    {
-        var it = mem.tokenize(includes_output, " \r\n");
-        while (it.next()) |include_arg| {
-            if (mem.startsWith(u8, include_arg, "-I")) {
-                try result.includes.append(include_arg[2..]);
-            } else {
-                try result.includes.append(include_arg);
-            }
-        }
-    }
-    {
-        var it = mem.tokenize(libdir_output, " \r\n");
-        while (it.next()) |libdir| {
-            if (mem.startsWith(u8, libdir, "-L")) {
-                try result.libdirs.append(libdir[2..]);
-            } else {
-                try result.libdirs.append(libdir);
-            }
-        }
-    }
-    return result;
-}
-
-fn configureStage2(b: *Builder, exe: anytype, ctx: Context, need_cpp_includes: bool) !void {
-    exe.addIncludeDir("src");
-    exe.addIncludeDir(ctx.cmake_binary_dir);
-    addCppLib(b, exe, ctx.cmake_binary_dir, "zigcpp");
-    assert(ctx.lld_include_dir.len != 0);
-    exe.addIncludeDir(ctx.lld_include_dir);
-    {
-        var it = mem.tokenize(ctx.lld_libraries, ";");
-        while (it.next()) |lib| {
-            exe.addObjectFile(lib);
-        }
-    }
-    {
-        var it = mem.tokenize(ctx.clang_libraries, ";");
-        while (it.next()) |lib| {
-            exe.addObjectFile(lib);
-        }
-    }
-    dependOnLib(b, exe, ctx.llvm);
-
-    // Boy, it sure would be nice to simply linkSystemLibrary("c++") and rely on zig's
-    // ability to provide libc++ right? Well thanks to C++ not having a stable ABI this
-    // will cause linker errors. It would work in the situation when `zig cc` is used to
-    // build LLVM, Clang, and LLD, however when depending on them as system libraries, system
-    // libc++ must be used.
-    const cross_compile = false; // TODO
-    if (cross_compile) {
-        // In this case we assume that zig cc was used to build the LLVM, Clang, LLD dependencies.
-        exe.linkSystemLibrary("c++");
-    } else {
-        if (exe.target.getOsTag() == .linux) {
-            // First we try to static link against gcc libstdc++. If that doesn't work,
-            // we fall back to -lc++ and cross our fingers.
-            addCxxKnownPath(b, ctx, exe, "libstdc++.a", "", need_cpp_includes) catch |err| switch (err) {
-                error.RequiredLibraryNotFound => {
-                    exe.linkSystemLibrary("c++");
-                },
-                else => |e| return e,
-            };
-
-            exe.linkSystemLibrary("pthread");
-        } else if (exe.target.isFreeBSD()) {
-            try addCxxKnownPath(b, ctx, exe, "libc++.a", null, need_cpp_includes);
-            exe.linkSystemLibrary("pthread");
-        } else if (exe.target.isDarwin()) {
-            if (addCxxKnownPath(b, ctx, exe, "libgcc_eh.a", "", need_cpp_includes)) {
-                // Compiler is GCC.
-                try addCxxKnownPath(b, ctx, exe, "libstdc++.a", null, need_cpp_includes);
-                exe.linkSystemLibrary("pthread");
-                // TODO LLD cannot perform this link.
-                // Set ZIG_SYSTEM_LINKER_HACK env var to use system linker ld instead.
-                // See https://github.com/ziglang/zig/issues/1535
-            } else |err| switch (err) {
-                error.RequiredLibraryNotFound => {
-                    // System compiler, not gcc.
-                    exe.linkSystemLibrary("c++");
-                },
-                else => |e| return e,
-            }
-        }
-
-        if (ctx.dia_guids_lib.len != 0) {
-            exe.addObjectFile(ctx.dia_guids_lib);
-        }
-    }
-}
-
 fn addCxxKnownPath(
     b: *Builder,
     ctx: CMakeConfig,
diff --git a/lib/std/array_list_sentineled.zig b/lib/std/array_list_sentineled.zig
deleted file mode 100644
index 323b5eaaed..0000000000
--- a/lib/std/array_list_sentineled.zig
+++ /dev/null
@@ -1,229 +0,0 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2015-2020 Zig Contributors
-// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
-// The MIT license requires this copyright notice to be included in all copies
-// and substantial portions of the software.
-const std = @import("std.zig");
-const debug = std.debug;
-const mem = std.mem;
-const Allocator = mem.Allocator;
-const assert = debug.assert;
-const testing = std.testing;
-const ArrayList = std.ArrayList;
-
-/// A contiguous, growable list of items in memory, with a sentinel after them.
-/// The sentinel is maintained when appending, resizing, etc.
-/// If you do not need a sentinel, consider using `ArrayList` instead.
-pub fn ArrayListSentineled(comptime T: type, comptime sentinel: T) type {
-    return struct {
-        list: ArrayList(T),
-
-        const Self = @This();
-
-        /// Must deinitialize with deinit.
-        pub fn init(allocator: *Allocator, m: []const T) !Self {
-            var self = try initSize(allocator, m.len);
-            mem.copy(T, self.list.items, m);
-            return self;
-        }
-
-        /// Initialize memory to size bytes of undefined values.
-        /// Must deinitialize with deinit.
-        pub fn initSize(allocator: *Allocator, size: usize) !Self {
-            var self = initNull(allocator);
-            try self.resize(size);
-            return self;
-        }
-
-        /// Initialize with capacity to hold at least num bytes.
-        /// Must deinitialize with deinit.
-        pub fn initCapacity(allocator: *Allocator, num: usize) !Self {
-            var self = Self{ .list = try ArrayList(T).initCapacity(allocator, num + 1) };
-            self.list.appendAssumeCapacity(sentinel);
-            return self;
-        }
-
-        /// Must deinitialize with deinit.
-        /// None of the other operations are valid until you do one of these:
-        /// * `replaceContents`
-        /// * `resize`
-        pub fn initNull(allocator: *Allocator) Self {
-            return Self{ .list = ArrayList(T).init(allocator) };
-        }
-
-        /// Must deinitialize with deinit.
-        pub fn initFromBuffer(buffer: Self) !Self {
-            return Self.init(buffer.list.allocator, buffer.span());
-        }
-
-        /// Takes ownership of the passed in slice. The slice must have been
-        /// allocated with `allocator`.
-        /// Must deinitialize with deinit.
-        pub fn fromOwnedSlice(allocator: *Allocator, slice: []T) !Self {
-            var self = Self{ .list = ArrayList(T).fromOwnedSlice(allocator, slice) };
-            try self.list.append(sentinel);
-            return self;
-        }
-
-        /// The caller owns the returned memory. The list becomes null and is safe to `deinit`.
-        pub fn toOwnedSlice(self: *Self) [:sentinel]T {
-            const allocator = self.list.allocator;
-            const result = self.list.toOwnedSlice();
-            self.* = initNull(allocator);
-            return result[0 .. result.len - 1 :sentinel];
-        }
-
-        /// Only works when `T` is `u8`.
-        pub fn allocPrint(allocator: *Allocator, comptime format: []const u8, args: anytype) !Self {
-            const size = std.math.cast(usize, std.fmt.count(format, args)) catch |err| switch (err) {
-                error.Overflow => return error.OutOfMemory,
-            };
-            var self = try Self.initSize(allocator, size);
-            assert((std.fmt.bufPrint(self.list.items, format, args) catch unreachable).len == size);
-            return self;
-        }
-
-        pub fn deinit(self: *Self) void {
-            self.list.deinit();
-        }
-
-        pub fn span(self: anytype) @TypeOf(self.list.items[0..:sentinel]) {
-            return self.list.items[0..self.len() :sentinel];
-        }
-
-        pub fn shrink(self: *Self, new_len: usize) void {
-            assert(new_len <= self.len());
-            self.list.shrink(new_len + 1);
-            self.list.items[self.len()] = sentinel;
-        }
-
-        pub fn resize(self: *Self, new_len: usize) !void {
-            try self.list.resize(new_len + 1);
-            self.list.items[self.len()] = sentinel;
-        }
-
-        pub fn isNull(self: Self) bool {
-            return self.list.items.len == 0;
-        }
-
-        pub fn len(self: Self) usize {
-            return self.list.items.len - 1;
-        }
-
-        pub fn capacity(self: Self) usize {
-            return if (self.list.capacity > 0)
-                self.list.capacity - 1
-            else
-                0;
-        }
-
-        pub fn appendSlice(self: *Self, m: []const T) !void {
-            const old_len = self.len();
-            try self.resize(old_len + m.len);
-            mem.copy(T, self.list.items[old_len..], m);
-        }
-
-        pub fn append(self: *Self, byte: T) !void {
-            const old_len = self.len();
-            try self.resize(old_len + 1);
-            self.list.items[old_len] = byte;
-        }
-
-        pub fn eql(self: Self, m: []const T) bool {
-            return mem.eql(T, self.span(), m);
-        }
-
-        pub fn startsWith(self: Self, m: []const T) bool {
-            if (self.len() < m.len) return false;
-            return mem.eql(T, self.list.items[0..m.len], m);
-        }
-
-        pub fn endsWith(self: Self, m: []const T) bool {
-            const l = self.len();
-            if (l < m.len) return false;
-            const start = l - m.len;
-            return mem.eql(T, self.list.items[start..l], m);
-        }
-
-        pub fn replaceContents(self: *Self, m: []const T) !void {
-            try self.resize(m.len);
-            mem.copy(T, self.list.items, m);
-        }
-
-        /// Initializes an OutStream which will append to the list.
-        /// This function may be called only when `T` is `u8`.
-        pub fn outStream(self: *Self) std.io.OutStream(*Self, error{OutOfMemory}, appendWrite) {
-            return .{ .context = self };
-        }
-
-        /// Same as `append` except it returns the number of bytes written, which is always the same
-        /// as `m.len`. The purpose of this function existing is to match `std.io.OutStream` API.
-        /// This function may be called only when `T` is `u8`.
-        pub fn appendWrite(self: *Self, m: []const u8) !usize {
-            try self.appendSlice(m);
-            return m.len;
-        }
-    };
-}
-
-test "simple" {
-    var buf = try ArrayListSentineled(u8, 0).init(testing.allocator, "");
-    defer buf.deinit();
-
-    testing.expect(buf.len() == 0);
-    try buf.appendSlice("hello");
-    try buf.appendSlice(" ");
-    try buf.appendSlice("world");
-    testing.expect(buf.eql("hello world"));
-    testing.expect(mem.eql(u8, mem.spanZ(buf.span().ptr), buf.span()));
-
-    var buf2 = try ArrayListSentineled(u8, 0).initFromBuffer(buf);
-    defer buf2.deinit();
-    testing.expect(buf.eql(buf2.span()));
-
-    testing.expect(buf.startsWith("hell"));
-    testing.expect(buf.endsWith("orld"));
-
-    try buf2.resize(4);
-    testing.expect(buf.startsWith(buf2.span()));
-}
-
-test "initSize" {
-    var buf = try ArrayListSentineled(u8, 0).initSize(testing.allocator, 3);
-    defer buf.deinit();
-    testing.expect(buf.len() == 3);
-    try buf.appendSlice("hello");
-    testing.expect(mem.eql(u8, buf.span()[3..], "hello"));
-}
-
-test "initCapacity" {
-    var buf = try ArrayListSentineled(u8, 0).initCapacity(testing.allocator, 10);
-    defer buf.deinit();
-    testing.expect(buf.len() == 0);
-    testing.expect(buf.capacity() >= 10);
-    const old_cap = buf.capacity();
-    try buf.appendSlice("hello");
-    testing.expect(buf.len() == 5);
-    testing.expect(buf.capacity() == old_cap);
-    testing.expect(mem.eql(u8, buf.span(), "hello"));
-}
-
-test "print" {
-    var buf = try ArrayListSentineled(u8, 0).init(testing.allocator, "");
-    defer buf.deinit();
-
-    try buf.outStream().print("Hello {d} the {s}", .{ 2, "world" });
-    testing.expect(buf.eql("Hello 2 the world"));
-}
-
-test "outStream" {
-    var buffer = try ArrayListSentineled(u8, 0).initSize(testing.allocator, 0);
-    defer buffer.deinit();
-    const buf_stream = buffer.outStream();
-
-    const x: i32 = 42;
-    const y: i32 = 1234;
-    try buf_stream.print("x: {}\ny: {}\n", .{ x, y });
-
-    testing.expect(mem.eql(u8, buffer.span(), "x: 42\ny: 1234\n"));
-}
diff --git a/lib/std/progress.zig b/lib/std/progress.zig
deleted file mode 100644
index 474ed050aa..0000000000
--- a/lib/std/progress.zig
+++ /dev/null
@@ -1,310 +0,0 @@
-// SPDX-License-Identifier: MIT
-// Copyright (c) 2015-2020 Zig Contributors
-// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
-// The MIT license requires this copyright notice to be included in all copies
-// and substantial portions of the software.
-const std = @import("std");
-const windows = std.os.windows;
-const testing = std.testing;
-const assert = std.debug.assert;
-
-/// This API is non-allocating and non-fallible. The tradeoff is that users of
-/// this API must provide the storage for each `Progress.Node`.
-/// Initialize the struct directly, overriding these fields as desired:
-/// * `refresh_rate_ms`
-/// * `initial_delay_ms`
-pub const Progress = struct {
-    /// `null` if the current node (and its children) should
-    /// not print on update()
-    terminal: ?std.fs.File = undefined,
-
-    /// Whether the terminal supports ANSI escape codes.
-    supports_ansi_escape_codes: bool = false,
-
-    root: Node = undefined,
-
-    /// Keeps track of how much time has passed since the beginning.
-    /// Used to compare with `initial_delay_ms` and `refresh_rate_ms`.
-    timer: std.time.Timer = undefined,
-
-    /// When the previous refresh was written to the terminal.
-    /// Used to compare with `refresh_rate_ms`.
-    prev_refresh_timestamp: u64 = undefined,
-
-    /// This buffer represents the maximum number of bytes written to the terminal
-    /// with each refresh.
-    output_buffer: [100]u8 = undefined,
-
-    /// How many nanoseconds between writing updates to the terminal.
-    refresh_rate_ns: u64 = 50 * std.time.ns_per_ms,
-
-    /// How many nanoseconds to keep the output hidden
-    initial_delay_ns: u64 = 500 * std.time.ns_per_ms,
-
-    done: bool = true,
-
-    /// Keeps track of how many columns in the terminal have been output, so that
-    /// we can move the cursor back later.
-    columns_written: usize = undefined,
-
-    /// Represents one unit of progress. Each node can have children nodes, or
-    /// one can use integers with `update`.
-    pub const Node = struct {
-        context: *Progress,
-        parent: ?*Node,
-        completed_items: usize,
-        name: []const u8,
-        recently_updated_child: ?*Node = null,
-
-        /// This field may be updated freely.
-        estimated_total_items: ?usize,
-
-        /// Create a new child progress node.
-        /// Call `Node.end` when done.
-        /// TODO solve https://github.com/ziglang/zig/issues/2765 and then change this
-        /// API to set `self.parent.recently_updated_child` with the return value.
-        /// Until that is fixed you probably want to call `activate` on the return value.
-        pub fn start(self: *Node, name: []const u8, estimated_total_items: ?usize) Node {
-            return Node{
-                .context = self.context,
-                .parent = self,
-                .completed_items = 0,
-                .name = name,
-                .estimated_total_items = estimated_total_items,
-            };
-        }
-
-        /// This is the same as calling `start` and then `end` on the returned `Node`.
-        pub fn completeOne(self: *Node) void {
-            if (self.parent) |parent| parent.recently_updated_child = self;
-            self.completed_items += 1;
-            self.context.maybeRefresh();
-        }
-
-        pub fn end(self: *Node) void {
-            self.context.maybeRefresh();
-            if (self.parent) |parent| {
-                if (parent.recently_updated_child) |parent_child| {
-                    if (parent_child == self) {
-                        parent.recently_updated_child = null;
-                    }
-                }
-                parent.completeOne();
-            } else {
-                self.context.done = true;
-                self.context.refresh();
-            }
-        }
-
-        /// Tell the parent node that this node is actively being worked on.
-        pub fn activate(self: *Node) void {
-            if (self.parent) |parent| parent.recently_updated_child = self;
-        }
-    };
-
-    /// Create a new progress node.
-    /// Call `Node.end` when done.
-    /// TODO solve https://github.com/ziglang/zig/issues/2765 and then change this
-    /// API to return Progress rather than accept it as a parameter.
-    pub fn start(self: *Progress, name: []const u8, estimated_total_items: ?usize) !*Node {
-        const stderr = std.io.getStdErr();
-        self.terminal = null;
-        if (stderr.supportsAnsiEscapeCodes()) {
-            self.terminal = stderr;
-            self.supports_ansi_escape_codes = true;
-        } else if (std.builtin.os.tag == .windows and stderr.isTty()) {
-            self.terminal = stderr;
-        }
-        self.root = Node{
-            .context = self,
-            .parent = null,
-            .completed_items = 0,
-            .name = name,
-            .estimated_total_items = estimated_total_items,
-        };
-        self.columns_written = 0;
-        self.prev_refresh_timestamp = 0;
-        self.timer = try std.time.Timer.start();
-        self.done = false;
-        return &self.root;
-    }
-
-    /// Updates the terminal if enough time has passed since last update.
-    pub fn maybeRefresh(self: *Progress) void {
-        const now = self.timer.read();
-        if (now < self.initial_delay_ns) return;
-        if (now - self.prev_refresh_timestamp < self.refresh_rate_ns) return;
-        self.refresh();
-    }
-
-    /// Updates the terminal and resets `self.next_refresh_timestamp`.
-    pub fn refresh(self: *Progress) void {
-        const file = self.terminal orelse return;
-
-        const prev_columns_written = self.columns_written;
-        var end: usize = 0;
-        if (self.columns_written > 0) {
-            // restore the cursor position by moving the cursor
-            // `columns_written` cells to the left, then clear the rest of the
-            // line
-            if (self.supports_ansi_escape_codes) {
-                end += (std.fmt.bufPrint(self.output_buffer[end..], "\x1b[{d}D", .{self.columns_written}) catch unreachable).len;
-                end += (std.fmt.bufPrint(self.output_buffer[end..], "\x1b[0K", .{}) catch unreachable).len;
-            } else if (std.builtin.os.tag == .windows) winapi: {
-                var info: windows.CONSOLE_SCREEN_BUFFER_INFO = undefined;
-                if (windows.kernel32.GetConsoleScreenBufferInfo(file.handle, &info) != windows.TRUE)
-                    unreachable;
-
-                var cursor_pos = windows.COORD{
-                    .X = info.dwCursorPosition.X - @intCast(windows.SHORT, self.columns_written),
-                    .Y = info.dwCursorPosition.Y,
-                };
-
-                if (cursor_pos.X < 0)
-                    cursor_pos.X = 0;
-
-                const fill_chars = @intCast(windows.DWORD, info.dwSize.X - cursor_pos.X);
-
-                var written: windows.DWORD = undefined;
-                if (windows.kernel32.FillConsoleOutputAttribute(
-                    file.handle,
-                    info.wAttributes,
-                    fill_chars,
-                    cursor_pos,
-                    &written,
-                ) != windows.TRUE) {
-                    // Stop trying to write to this file.
-                    self.terminal = null;
-                    break :winapi;
-                }
-                if (windows.kernel32.FillConsoleOutputCharacterA(
-                    file.handle,
-                    ' ',
-                    fill_chars,
-                    cursor_pos,
-                    &written,
-                ) != windows.TRUE) unreachable;
-
-                if (windows.kernel32.SetConsoleCursorPosition(file.handle, cursor_pos) != windows.TRUE)
-                    unreachable;
-            } else unreachable;
-
-            self.columns_written = 0;
-        }
-
-        if (!self.done) {
-            var need_ellipse = false;
-            var maybe_node: ?*Node = &self.root;
-            while (maybe_node) |node| {
-                if (need_ellipse) {
-                    self.bufWrite(&end, "... ", .{});
-                }
-                need_ellipse = false;
-                if (node.name.len != 0 or node.estimated_total_items != null) {
-                    if (node.name.len != 0) {
-                        self.bufWrite(&end, "{s}", .{node.name});
-                        need_ellipse = true;
-                    }
-                    if (node.estimated_total_items) |total| {
-                        if (need_ellipse) self.bufWrite(&end, " ", .{});
-                        self.bufWrite(&end, "[{d}/{d}] ", .{ node.completed_items + 1, total });
-                        need_ellipse = false;
-                    } else if (node.completed_items != 0) {
-                        if (need_ellipse) self.bufWrite(&end, " ", .{});
-                        self.bufWrite(&end, "[{d}] ", .{node.completed_items + 1});
-                        need_ellipse = false;
-                    }
-                }
-                maybe_node = node.recently_updated_child;
-            }
-            if (need_ellipse) {
-                self.bufWrite(&end, "... ", .{});
-            }
-        }
-
-        _ = file.write(self.output_buffer[0..end]) catch |e| {
-            // Stop trying to write to this file once it errors.
-            self.terminal = null;
-        };
-        self.prev_refresh_timestamp = self.timer.read();
-    }
-
-    pub fn log(self: *Progress, comptime format: []const u8, args: anytype) void {
-        const file = self.terminal orelse return;
-        self.refresh();
-        file.outStream().print(format, args) catch {
-            self.terminal = null;
-            return;
-        };
-        self.columns_written = 0;
-    }
-
-    fn bufWrite(self: *Progress, end: *usize, comptime format: []const u8, args: anytype) void {
-        if (std.fmt.bufPrint(self.output_buffer[end.*..], format, args)) |written| {
-            const amt = written.len;
-            end.* += amt;
-            self.columns_written += amt;
-        } else |err| switch (err) {
-            error.NoSpaceLeft => {
-                self.columns_written += self.output_buffer.len - end.*;
-                end.* = self.output_buffer.len;
-            },
-        }
-        const bytes_needed_for_esc_codes_at_end = if (std.builtin.os.tag == .windows) 0 else 11;
-        const max_end = self.output_buffer.len - bytes_needed_for_esc_codes_at_end;
-        if (end.* > max_end) {
-            const suffix = "... ";
-            self.columns_written = self.columns_written - (end.* - max_end) + suffix.len;
-            std.mem.copy(u8, self.output_buffer[max_end..], suffix);
-            end.* = max_end + suffix.len;
-        }
-    }
-};
-
-test "basic functionality" {
-    var disable = true;
-    if (disable) {
-        // This test is disabled because it uses time.sleep() and is therefore slow. It also
-        // prints bogus progress data to stderr.
-        return error.SkipZigTest;
-    }
-    var progress = Progress{};
-    const root_node = try progress.start("", 100);
-    defer root_node.end();
-
-    const sub_task_names = [_][]const u8{
-        "reticulating splines",
-        "adjusting shoes",
-        "climbing towers",
-        "pouring juice",
-    };
-    var next_sub_task: usize = 0;
-
-    var i: usize = 0;
-    while (i < 100) : (i += 1) {
-        var node = root_node.start(sub_task_names[next_sub_task], 5);
-        node.activate();
-        next_sub_task = (next_sub_task + 1) % sub_task_names.len;
-
-        node.completeOne();
-        std.time.sleep(5 * std.time.ns_per_ms);
-        node.completeOne();
-        node.completeOne();
-        std.time.sleep(5 * std.time.ns_per_ms);
-        node.completeOne();
-        node.completeOne();
-        std.time.sleep(5 * std.time.ns_per_ms);
-
-        node.end();
-
-        std.time.sleep(5 * std.time.ns_per_ms);
-    }
-    {
-        var node = root_node.start("this is a really long name designed to activate the truncation code. let's find out if it works", null);
-        node.activate();
-        std.time.sleep(10 * std.time.ns_per_ms);
-        progress.refresh();
-        std.time.sleep(10 * std.time.ns_per_ms);
-        node.end();
-    }
-}
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index b97e1590e3..37654b8ce0 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -481,9 +481,8 @@ fn genBinOp(ctx: *Context, file: *C, inst: *Inst.BinOp, operator: []const u8) !?
     const rhs = try ctx.resolveInst(inst.rhs);
     const writer = file.main.writer();
     const name = try ctx.name();
-    try writer.writeAll(indentation ++ "const ");
-    try renderType(ctx, writer, inst.base.ty);
-    try writer.print(" {s} = {s} " ++ operator ++ " {s};\n", .{ name, lhs, rhs });
+    try renderTypeAndName(ctx, writer, inst.base.ty, name, .Const);
+    try writer.print(" = {s} {s} {s};\n", .{ lhs, operator, rhs });
     return name;
 }
 
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
deleted file mode 100644
index 3a1ebada3b..0000000000
--- a/src/codegen/llvm.zig
+++ /dev/null
@@ -1,125 +0,0 @@
-const std = @import("std");
-const Allocator = std.mem.Allocator;
-
-pub fn targetTriple(allocator: *Allocator, target: std.Target) ![]u8 {
-    const llvm_arch = switch (target.cpu.arch) {
-        .arm => "arm",
-        .armeb => "armeb",
-        .aarch64 => "aarch64",
-        .aarch64_be => "aarch64_be",
-        .aarch64_32 => "aarch64_32",
-        .arc => "arc",
-        .avr => "avr",
-        .bpfel => "bpfel",
-        .bpfeb => "bpfeb",
-        .hexagon => "hexagon",
-        .mips => "mips",
-        .mipsel => "mipsel",
-        .mips64 => "mips64",
-        .mips64el => "mips64el",
-        .msp430 => "msp430",
-        .powerpc => "powerpc",
-        .powerpc64 => "powerpc64",
-        .powerpc64le => "powerpc64le",
-        .r600 => "r600",
-        .amdgcn => "amdgcn",
-        .riscv32 => "riscv32",
-        .riscv64 => "riscv64",
-        .sparc => "sparc",
-        .sparcv9 => "sparcv9",
-        .sparcel => "sparcel",
-        .s390x => "s390x",
-        .tce => "tce",
-        .tcele => "tcele",
-        .thumb => "thumb",
-        .thumbeb => "thumbeb",
-        .i386 => "i386",
-        .x86_64 => "x86_64",
-        .xcore => "xcore",
-        .nvptx => "nvptx",
-        .nvptx64 => "nvptx64",
-        .le32 => "le32",
-        .le64 => "le64",
-        .amdil => "amdil",
-        .amdil64 => "amdil64",
-        .hsail => "hsail",
-        .hsail64 => "hsail64",
-        .spir => "spir",
-        .spir64 => "spir64",
-        .kalimba => "kalimba",
-        .shave => "shave",
-        .lanai => "lanai",
-        .wasm32 => "wasm32",
-        .wasm64 => "wasm64",
-        .renderscript32 => "renderscript32",
-        .renderscript64 => "renderscript64",
-        .ve => "ve",
-        .spu_2 => return error.LLVMBackendDoesNotSupportSPUMarkII,
-    };
-    // TODO Add a sub-arch for some architectures depending on CPU features.
-
-    const llvm_os = switch (target.os.tag) {
-        .freestanding => "unknown",
-        .ananas => "ananas",
-        .cloudabi => "cloudabi",
-        .dragonfly => "dragonfly",
-        .freebsd => "freebsd",
-        .fuchsia => "fuchsia",
-        .ios => "ios",
-        .kfreebsd => "kfreebsd",
-        .linux => "linux",
-        .lv2 => "lv2",
-        .macos => "macosx",
-        .netbsd => "netbsd",
-        .openbsd => "openbsd",
-        .solaris => "solaris",
-        .windows => "windows",
-        .haiku => "haiku",
-        .minix => "minix",
-        .rtems => "rtems",
-        .nacl => "nacl",
-        .cnk => "cnk",
-        .aix => "aix",
-        .cuda => "cuda",
-        .nvcl => "nvcl",
-        .amdhsa => "amdhsa",
-        .ps4 => "ps4",
-        .elfiamcu => "elfiamcu",
-        .tvos => "tvos",
-        .watchos => "watchos",
-        .mesa3d => "mesa3d",
-        .contiki => "contiki",
-        .amdpal => "amdpal",
-        .hermit => "hermit",
-        .hurd => "hurd",
-        .wasi => "wasi",
-        .emscripten => "emscripten",
-        .uefi => "windows",
-        .other => "unknown",
-    };
-
-    const llvm_abi = switch (target.abi) {
-        .none => "unknown",
-        .gnu => "gnu",
-        .gnuabin32 => "gnuabin32",
-        .gnuabi64 => "gnuabi64",
-        .gnueabi => "gnueabi",
-        .gnueabihf => "gnueabihf",
-        .gnux32 => "gnux32",
-        .code16 => "code16",
-        .eabi => "eabi",
-        .eabihf => "eabihf",
-        .android => "android",
-        .musl => "musl",
-        .musleabi => "musleabi",
-        .musleabihf => "musleabihf",
-        .msvc => "msvc",
-        .itanium => "itanium",
-        .cygnus => "cygnus",
-        .coreclr => "coreclr",
-        .simulator => "simulator",
-        .macabi => "macabi",
-    };
-
-    return std.fmt.allocPrint(allocator, "{s}-unknown-{s}-{s}", .{ llvm_arch, llvm_os, llvm_abi });
-}
diff --git a/src/link/C.zig b/src/link/C.zig
index 3ac9db717f..c3ab506b2c 100644
--- a/src/link/C.zig
+++ b/src/link/C.zig
@@ -111,9 +111,6 @@ pub fn flushModule(self: *C, comp: *Compilation) !void {
     if (self.header.buf.items.len > 0) {
         try writer.writeByte('\n');
     }
-    if (self.header.items.len > 0) {
-        try writer.print("{s}\n", .{self.header.items});
-    }
     if (self.constants.items.len > 0) {
         try writer.print("{s}\n", .{self.constants.items});
     }
diff --git a/src/llvm_backend.zig b/src/llvm_backend.zig
index 294e6f5400..51d1a0840e 100644
--- a/src/llvm_backend.zig
+++ b/src/llvm_backend.zig
@@ -132,7 +132,7 @@ pub fn targetTriple(allocator: *Allocator, target: std.Target) ![:0]u8 {
         .macabi => "macabi",
     };
 
-    return std.fmt.allocPrintZ(allocator, "{}-unknown-{}-{}", .{ llvm_arch, llvm_os, llvm_abi });
+    return std.fmt.allocPrintZ(allocator, "{s}-unknown-{s}-{s}", .{ llvm_arch, llvm_os, llvm_abi });
 }
 
 pub const LLVMIRModule = struct {

From 974c008a0ee0e0d7933e37d5ea930f712d494f6a Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sat, 2 Jan 2021 19:03:14 -0700
Subject: [PATCH 16/16] convert more {} to {d} and {s}

---
 lib/std/SemanticVersion.zig     |  2 +-
 lib/std/c/ast.zig               |  8 ++++----
 lib/std/fs/wasi.zig             |  2 +-
 lib/std/os.zig                  |  4 ++--
 lib/std/special/c.zig           |  2 +-
 lib/std/special/compiler_rt.zig |  2 +-
 lib/std/testing.zig             |  2 +-
 lib/std/zig/parser_test.zig     |  4 ++--
 lib/std/zig/system/macos.zig    |  4 ++--
 src/Compilation.zig             | 12 ++++++------
 src/DepTokenizer.zig            |  6 +++---
 src/Module.zig                  | 22 +++++++++++-----------
 src/astgen.zig                  |  6 +++---
 src/codegen/c.zig               |  6 +++---
 src/glibc.zig                   | 28 ++++++++++++++--------------
 src/link.zig                    |  2 +-
 src/link/Elf.zig                |  6 +++---
 src/liveness.zig                |  3 ++-
 src/main.zig                    | 14 +++++++-------
 src/translate_c.zig             | 18 +++++++++---------
 src/type.zig                    |  8 ++++----
 src/zir.zig                     | 19 +++++++++----------
 src/zir_sema.zig                | 14 +++++++-------
 23 files changed, 97 insertions(+), 97 deletions(-)

diff --git a/lib/std/SemanticVersion.zig b/lib/std/SemanticVersion.zig
index eeb6916ad6..dc9e6d8572 100644
--- a/lib/std/SemanticVersion.zig
+++ b/lib/std/SemanticVersion.zig
@@ -163,7 +163,7 @@ pub fn format(
     out_stream: anytype,
 ) !void {
     if (fmt.len != 0) @compileError("Unknown format string: '" ++ fmt ++ "'");
-    try std.fmt.format(out_stream, "{}.{}.{}", .{ self.major, self.minor, self.patch });
+    try std.fmt.format(out_stream, "{d}.{d}.{d}", .{ self.major, self.minor, self.patch });
     if (self.pre) |pre| try std.fmt.format(out_stream, "-{s}", .{pre});
     if (self.build) |build| try std.fmt.format(out_stream, "+{s}", .{build});
 }
diff --git a/lib/std/c/ast.zig b/lib/std/c/ast.zig
index c1e20f799d..207fe8eac8 100644
--- a/lib/std/c/ast.zig
+++ b/lib/std/c/ast.zig
@@ -115,10 +115,10 @@ pub const Error = union(enum) {
         pub fn render(self: *const ExpectedToken, tree: *Tree, stream: anytype) !void {
             const found_token = tree.tokens.at(self.token);
             if (found_token.id == .Invalid) {
-                return stream.print("expected '{}', found invalid bytes", .{self.expected_id.symbol()});
+                return stream.print("expected '{s}', found invalid bytes", .{self.expected_id.symbol()});
             } else {
                 const token_name = found_token.id.symbol();
-                return stream.print("expected '{}', found '{}'", .{ self.expected_id.symbol(), token_name });
+                return stream.print("expected '{s}', found '{s}'", .{ self.expected_id.symbol(), token_name });
             }
         }
     };
@@ -131,7 +131,7 @@ pub const Error = union(enum) {
             try stream.write("invalid type specifier '");
             try type_spec.spec.print(tree, stream);
             const token_name = tree.tokens.at(self.token).id.symbol();
-            return stream.print("{}'", .{token_name});
+            return stream.print("{s}'", .{token_name});
         }
     };
 
@@ -140,7 +140,7 @@ pub const Error = union(enum) {
         name: TokenIndex,
 
         pub fn render(self: *const ExpectedToken, tree: *Tree, stream: anytype) !void {
-            return stream.print("must use '{}' tag to refer to type '{}'", .{ tree.slice(kw), tree.slice(name) });
+            return stream.print("must use '{s}' tag to refer to type '{s}'", .{ tree.slice(kw), tree.slice(name) });
         }
     };
 
diff --git a/lib/std/fs/wasi.zig b/lib/std/fs/wasi.zig
index 761f6e8466..900adc5e2d 100644
--- a/lib/std/fs/wasi.zig
+++ b/lib/std/fs/wasi.zig
@@ -38,7 +38,7 @@ pub const PreopenType = union(PreopenTypeTag) {
     pub fn format(self: Self, comptime fmt: []const u8, options: std.fmt.FormatOptions, out_stream: anytype) !void {
         try out_stream.print("PreopenType{{ ", .{});
         switch (self) {
-            PreopenType.Dir => |path| try out_stream.print(".Dir = '{}'", .{path}),
+            PreopenType.Dir => |path| try out_stream.print(".Dir = '{z}'", .{path}),
         }
         return out_stream.print(" }}", .{});
     }
diff --git a/lib/std/os.zig b/lib/std/os.zig
index fb187252a1..1bde12a6fb 100644
--- a/lib/std/os.zig
+++ b/lib/std/os.zig
@@ -4256,7 +4256,7 @@ pub fn getFdPath(fd: fd_t, out_buffer: *[MAX_PATH_BYTES]u8) RealPathError![]u8 {
         },
         .linux => {
             var procfs_buf: ["/proc/self/fd/-2147483648".len:0]u8 = undefined;
-            const proc_path = std.fmt.bufPrint(procfs_buf[0..], "/proc/self/fd/{}\x00", .{fd}) catch unreachable;
+            const proc_path = std.fmt.bufPrint(procfs_buf[0..], "/proc/self/fd/{d}\x00", .{fd}) catch unreachable;
 
             const target = readlinkZ(std.meta.assumeSentinel(proc_path.ptr, 0), out_buffer) catch |err| {
                 switch (err) {
@@ -4487,7 +4487,7 @@ pub const UnexpectedError = error{
 /// and you get an unexpected error.
 pub fn unexpectedErrno(err: usize) UnexpectedError {
     if (unexpected_error_tracing) {
-        std.debug.warn("unexpected errno: {}\n", .{err});
+        std.debug.warn("unexpected errno: {d}\n", .{err});
         std.debug.dumpCurrentStackTrace(null);
     }
     return error.Unexpected;
diff --git a/lib/std/special/c.zig b/lib/std/special/c.zig
index c92ffa21ac..51cbafc133 100644
--- a/lib/std/special/c.zig
+++ b/lib/std/special/c.zig
@@ -172,7 +172,7 @@ test "strncmp" {
 pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn {
     if (builtin.is_test) {
         @setCold(true);
-        std.debug.panic("{}", .{msg});
+        std.debug.panic("{s}", .{msg});
     }
     if (builtin.os.tag != .freestanding and builtin.os.tag != .other) {
         std.os.abort();
diff --git a/lib/std/special/compiler_rt.zig b/lib/std/special/compiler_rt.zig
index e0743cd4b7..a06c568b2e 100644
--- a/lib/std/special/compiler_rt.zig
+++ b/lib/std/special/compiler_rt.zig
@@ -324,7 +324,7 @@ pub usingnamespace @import("compiler_rt/atomics.zig");
 pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn {
     @setCold(true);
     if (is_test) {
-        std.debug.panic("{}", .{msg});
+        std.debug.panic("{s}", .{msg});
     } else {
         unreachable;
     }
diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index 80cc7f930d..4f4a46dbf7 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -258,7 +258,7 @@ pub fn expectEqualSlices(comptime T: type, expected: []const T, actual: []const
     // If the child type is u8 and no weird bytes, we could print it as strings
     // Even for the length difference, it would be useful to see the values of the slices probably.
     if (expected.len != actual.len) {
-        std.debug.panic("slice lengths differ. expected {}, found {}", .{ expected.len, actual.len });
+        std.debug.panic("slice lengths differ. expected {d}, found {d}", .{ expected.len, actual.len });
     }
     var i: usize = 0;
     while (i < expected.len) : (i += 1) {
diff --git a/lib/std/zig/parser_test.zig b/lib/std/zig/parser_test.zig
index a736006bc6..63d04f9a80 100644
--- a/lib/std/zig/parser_test.zig
+++ b/lib/std/zig/parser_test.zig
@@ -3742,7 +3742,7 @@ fn testParse(source: []const u8, allocator: *mem.Allocator, anything_changed: *b
     for (tree.errors) |*parse_error| {
         const token = tree.token_locs[parse_error.loc()];
         const loc = tree.tokenLocation(0, parse_error.loc());
-        try stderr.print("(memory buffer):{}:{}: error: ", .{ loc.line + 1, loc.column + 1 });
+        try stderr.print("(memory buffer):{d}:{d}: error: ", .{ loc.line + 1, loc.column + 1 });
         try tree.renderError(parse_error, stderr);
         try stderr.print("\n{s}\n", .{source[loc.line_start..loc.line_end]});
         {
@@ -3800,7 +3800,7 @@ fn testTransform(source: []const u8, expected_source: []const u8) !void {
             error.OutOfMemory => {
                 if (failing_allocator.allocated_bytes != failing_allocator.freed_bytes) {
                     warn(
-                        "\nfail_index: {}/{}\nallocated bytes: {}\nfreed bytes: {}\nallocations: {}\ndeallocations: {}\n",
+                        "\nfail_index: {d}/{d}\nallocated bytes: {d}\nfreed bytes: {d}\nallocations: {d}\ndeallocations: {d}\n",
                         .{
                             fail_index,
                             needed_alloc_count,
diff --git a/lib/std/zig/system/macos.zig b/lib/std/zig/system/macos.zig
index fbc0b5149b..7c4e255cc5 100644
--- a/lib/std/zig/system/macos.zig
+++ b/lib/std/zig/system/macos.zig
@@ -450,7 +450,7 @@ test "version_from_build" {
     for (known) |pair| {
         var buf: [32]u8 = undefined;
         const ver = try version_from_build(pair[0]);
-        const sver = try std.fmt.bufPrint(buf[0..], "{}.{}.{}", .{ ver.major, ver.minor, ver.patch });
+        const sver = try std.fmt.bufPrint(buf[0..], "{d}.{d}.{d}", .{ ver.major, ver.minor, ver.patch });
         std.testing.expect(std.mem.eql(u8, sver, pair[1]));
     }
 }
@@ -468,7 +468,7 @@ pub fn getSDKPath(allocator: *mem.Allocator) ![]u8 {
         allocator.free(result.stdout);
     }
     if (result.stderr.len != 0) {
-        std.log.err("unexpected 'xcrun --show-sdk-path' stderr: {}", .{result.stderr});
+        std.log.err("unexpected 'xcrun --show-sdk-path' stderr: {s}", .{result.stderr});
     }
     if (result.term.Exited != 0) {
         return error.ProcessTerminated;
diff --git a/src/Compilation.zig b/src/Compilation.zig
index c688cf7980..de115b9b40 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -1512,7 +1512,7 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
                             module.failed_decls.putAssumeCapacityNoClobber(decl, try ErrorMsg.create(
                                 module.gpa,
                                 decl.src(),
-                                "unable to generate C header: {}",
+                                "unable to generate C header: {s}",
                                 .{@errorName(err)},
                             ));
                             decl.analysis = .codegen_failure_retryable;
@@ -1593,7 +1593,7 @@ pub fn performAllTheWork(self: *Compilation) error{ TimerUnsupported, OutOfMemor
         .libtsan => {
             libtsan.buildTsan(self) catch |err| {
                 // TODO Expose this as a normal compile error rather than crashing here.
-                fatal("unable to build TSAN library: {}", .{@errorName(err)});
+                fatal("unable to build TSAN library: {s}", .{@errorName(err)});
             };
         },
         .compiler_rt_lib => {
@@ -1983,7 +1983,7 @@ fn updateCObject(comp: *Compilation, c_object: *CObject, c_comp_progress_node: *
                         // TODO parse clang stderr and turn it into an error message
                         // and then call failCObjWithOwnedErrorMsg
                         log.err("clang failed with stderr: {s}", .{stderr});
-                        return comp.failCObj(c_object, "clang exited with code {}", .{code});
+                        return comp.failCObj(c_object, "clang exited with code {d}", .{code});
                     }
                 },
                 else => {
@@ -3013,7 +3013,7 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
             id_symlink_basename,
             &prev_digest_buf,
         ) catch |err| blk: {
-            log.debug("stage1 {} new_digest={} error: {s}", .{ mod.root_pkg.root_src_path, digest, @errorName(err) });
+            log.debug("stage1 {s} new_digest={} error: {s}", .{ mod.root_pkg.root_src_path, digest, @errorName(err) });
             // Handle this as a cache miss.
             break :blk prev_digest_buf[0..0];
         };
@@ -3021,7 +3021,7 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
             if (!mem.eql(u8, prev_digest[0..digest.len], &digest))
                 break :hit;
 
-            log.debug("stage1 {} digest={} match - skipping invocation", .{ mod.root_pkg.root_src_path, digest });
+            log.debug("stage1 {s} digest={} match - skipping invocation", .{ mod.root_pkg.root_src_path, digest });
             var flags_bytes: [1]u8 = undefined;
             _ = std.fmt.hexToBytes(&flags_bytes, prev_digest[digest.len..]) catch {
                 log.warn("bad cache stage1 digest: '{s}'", .{prev_digest});
@@ -3044,7 +3044,7 @@ fn updateStage1Module(comp: *Compilation, main_progress_node: *std.Progress.Node
             mod.stage1_flags = @bitCast(@TypeOf(mod.stage1_flags), flags_bytes[0]);
             return;
         }
-        log.debug("stage1 {} prev_digest={} new_digest={}", .{ mod.root_pkg.root_src_path, prev_digest, digest });
+        log.debug("stage1 {s} prev_digest={} new_digest={}", .{ mod.root_pkg.root_src_path, prev_digest, digest });
         man.unhit(prev_hash_state, input_file_count);
     }
 
diff --git a/src/DepTokenizer.zig b/src/DepTokenizer.zig
index c42583a786..0872513b51 100644
--- a/src/DepTokenizer.zig
+++ b/src/DepTokenizer.zig
@@ -373,7 +373,7 @@ pub const Token = union(enum) {
                 } else {
                     try printCharValues(writer, index_and_bytes.bytes);
                 }
-                try writer.print("' at position {}", .{index_and_bytes.index});
+                try writer.print("' at position {d}", .{index_and_bytes.index});
             },
             .invalid_target,
             .bad_target_escape,
@@ -383,7 +383,7 @@ pub const Token = union(enum) {
             => |index_and_char| {
                 try writer.writeAll("illegal char ");
                 try printUnderstandableChar(writer, index_and_char.char);
-                try writer.print(" at position {}: {s}", .{ index_and_char.index, self.errStr() });
+                try writer.print(" at position {d}: {s}", .{ index_and_char.index, self.errStr() });
             },
         }
     }
@@ -943,7 +943,7 @@ fn printSection(out: anytype, label: []const u8, bytes: []const u8) !void {
 
 fn printLabel(out: anytype, label: []const u8, bytes: []const u8) !void {
     var buf: [80]u8 = undefined;
-    var text = try std.fmt.bufPrint(buf[0..], "{s} {} bytes ", .{ label, bytes.len });
+    var text = try std.fmt.bufPrint(buf[0..], "{s} {d} bytes ", .{ label, bytes.len });
     try out.writeAll(text);
     var i: usize = text.len;
     const end = 79;
diff --git a/src/Module.zig b/src/Module.zig
index 0d03703dcb..d1719059c4 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -248,7 +248,7 @@ pub const Decl = struct {
 
     pub fn dump(self: *Decl) void {
         const loc = std.zig.findLineColumn(self.scope.source.bytes, self.src);
-        std.debug.print("{}:{}:{} name={} status={}", .{
+        std.debug.print("{s}:{d}:{d} name={s} status={s}", .{
             self.scope.sub_file_path,
             loc.line + 1,
             loc.column + 1,
@@ -308,7 +308,7 @@ pub const Fn = struct {
 
     /// For debugging purposes.
     pub fn dump(self: *Fn, mod: Module) void {
-        std.debug.print("Module.Function(name={}) ", .{self.owner_decl.name});
+        std.debug.print("Module.Function(name={s}) ", .{self.owner_decl.name});
         switch (self.analysis) {
             .queued => {
                 std.debug.print("queued\n", .{});
@@ -632,7 +632,7 @@ pub const Scope = struct {
 
         pub fn dumpSrc(self: *File, src: usize) void {
             const loc = std.zig.findLineColumn(self.source.bytes, src);
-            std.debug.print("{}:{}:{}\n", .{ self.sub_file_path, loc.line + 1, loc.column + 1 });
+            std.debug.print("{s}:{d}:{d}\n", .{ self.sub_file_path, loc.line + 1, loc.column + 1 });
         }
 
         pub fn getSource(self: *File, module: *Module) ![:0]const u8 {
@@ -730,7 +730,7 @@ pub const Scope = struct {
 
         pub fn dumpSrc(self: *ZIRModule, src: usize) void {
             const loc = std.zig.findLineColumn(self.source.bytes, src);
-            std.debug.print("{}:{}:{}\n", .{ self.sub_file_path, loc.line + 1, loc.column + 1 });
+            std.debug.print("{s}:{d}:{d}\n", .{ self.sub_file_path, loc.line + 1, loc.column + 1 });
         }
 
         pub fn getSource(self: *ZIRModule, module: *Module) ![:0]const u8 {
@@ -1641,7 +1641,7 @@ pub fn analyzeContainer(self: *Module, container_scope: *Scope.Container) !void
             }
         } else if (src_decl.castTag(.Comptime)) |comptime_node| {
             const name_index = self.getNextAnonNameIndex();
-            const name = try std.fmt.allocPrint(self.gpa, "__comptime_{}", .{name_index});
+            const name = try std.fmt.allocPrint(self.gpa, "__comptime_{d}", .{name_index});
             defer self.gpa.free(name);
 
             const name_hash = container_scope.fullyQualifiedNameHash(name);
@@ -2277,7 +2277,7 @@ pub fn createAnonymousDecl(
 ) !*Decl {
     const name_index = self.getNextAnonNameIndex();
     const scope_decl = scope.decl().?;
-    const name = try std.fmt.allocPrint(self.gpa, "{s}__anon_{}", .{ scope_decl.name, name_index });
+    const name = try std.fmt.allocPrint(self.gpa, "{s}__anon_{d}", .{ scope_decl.name, name_index });
     defer self.gpa.free(name);
     const name_hash = scope.namespace().fullyQualifiedNameHash(name);
     const src_hash: std.zig.SrcHash = undefined;
@@ -2555,7 +2555,7 @@ pub fn cmpNumeric(
 
     if (lhs_ty_tag == .Vector and rhs_ty_tag == .Vector) {
         if (lhs.ty.arrayLen() != rhs.ty.arrayLen()) {
-            return self.fail(scope, src, "vector length mismatch: {} and {}", .{
+            return self.fail(scope, src, "vector length mismatch: {d} and {d}", .{
                 lhs.ty.arrayLen(),
                 rhs.ty.arrayLen(),
             });
@@ -2700,7 +2700,7 @@ pub fn cmpNumeric(
     const dest_type = if (dest_float_type) |ft| ft else blk: {
         const max_bits = std.math.max(lhs_bits, rhs_bits);
         const casted_bits = std.math.cast(u16, max_bits) catch |err| switch (err) {
-            error.Overflow => return self.fail(scope, src, "{} exceeds maximum integer bit count", .{max_bits}),
+            error.Overflow => return self.fail(scope, src, "{d} exceeds maximum integer bit count", .{max_bits}),
         };
         break :blk try self.makeIntType(scope, dest_int_is_signed, casted_bits);
     };
@@ -3319,7 +3319,7 @@ pub fn dumpInst(self: *Module, scope: *Scope, inst: *Inst) void {
     const source = zir_module.getSource(self) catch @panic("dumpInst failed to get source");
     const loc = std.zig.findLineColumn(source, inst.src);
     if (inst.tag == .constant) {
-        std.debug.print("constant ty={} val={} src={}:{}:{}\n", .{
+        std.debug.print("constant ty={} val={} src={s}:{d}:{d}\n", .{
             inst.ty,
             inst.castTag(.constant).?.val,
             zir_module.subFilePath(),
@@ -3327,7 +3327,7 @@ pub fn dumpInst(self: *Module, scope: *Scope, inst: *Inst) void {
             loc.column + 1,
         });
     } else if (inst.deaths == 0) {
-        std.debug.print("{} ty={} src={}:{}:{}\n", .{
+        std.debug.print("{s} ty={} src={s}:{d}:{d}\n", .{
             @tagName(inst.tag),
             inst.ty,
             zir_module.subFilePath(),
@@ -3335,7 +3335,7 @@ pub fn dumpInst(self: *Module, scope: *Scope, inst: *Inst) void {
             loc.column + 1,
         });
     } else {
-        std.debug.print("{} ty={} deaths={b} src={}:{}:{}\n", .{
+        std.debug.print("{s} ty={} deaths={b} src={s}:{d}:{d}\n", .{
             @tagName(inst.tag),
             inst.ty,
             inst.deaths,
diff --git a/src/astgen.zig b/src/astgen.zig
index b3cb648dcb..a50fa026ca 100644
--- a/src/astgen.zig
+++ b/src/astgen.zig
@@ -385,7 +385,7 @@ fn breakExpr(mod: *Module, parent_scope: *Scope, node: *ast.Node.ControlFlowExpr
             .local_ptr => scope = scope.cast(Scope.LocalPtr).?.parent,
             else => if (node.getLabel()) |break_label| {
                 const label_name = try identifierTokenString(mod, parent_scope, break_label);
-                return mod.failTok(parent_scope, break_label, "label not found: '{}'", .{label_name});
+                return mod.failTok(parent_scope, break_label, "label not found: '{s}'", .{label_name});
             } else {
                 return mod.failTok(parent_scope, src, "break expression outside loop", .{});
             },
@@ -427,7 +427,7 @@ fn continueExpr(mod: *Module, parent_scope: *Scope, node: *ast.Node.ControlFlowE
             .local_ptr => scope = scope.cast(Scope.LocalPtr).?.parent,
             else => if (node.getLabel()) |break_label| {
                 const label_name = try identifierTokenString(mod, parent_scope, break_label);
-                return mod.failTok(parent_scope, break_label, "label not found: '{}'", .{label_name});
+                return mod.failTok(parent_scope, break_label, "label not found: '{s}'", .{label_name});
             } else {
                 return mod.failTok(parent_scope, src, "continue expression outside loop", .{});
             },
@@ -2204,7 +2204,7 @@ fn ensureBuiltinParamCount(mod: *Module, scope: *Scope, call: *ast.Node.BuiltinC
         return;
 
     const s = if (count == 1) "" else "s";
-    return mod.failTok(scope, call.builtin_token, "expected {} parameter{s}, found {}", .{ count, s, call.params_len });
+    return mod.failTok(scope, call.builtin_token, "expected {d} parameter{s}, found {d}", .{ count, s, call.params_len });
 }
 
 fn simpleCast(
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 37654b8ce0..684a03eb79 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -383,7 +383,7 @@ const Context = struct {
     }
 
     fn name(self: *Context) ![]u8 {
-        const val = try std.fmt.allocPrint(&self.arena.allocator, "__temp_{}", .{self.unnamed_index});
+        const val = try std.fmt.allocPrint(&self.arena.allocator, "__temp_{d}", .{self.unnamed_index});
         self.unnamed_index += 1;
         return val;
     }
@@ -420,7 +420,7 @@ fn genAlloc(ctx: *Context, file: *C, alloc: *Inst.NoOp) !?[]u8 {
 }
 
 fn genArg(ctx: *Context) !?[]u8 {
-    const name = try std.fmt.allocPrint(&ctx.arena.allocator, "arg{}", .{ctx.argdex});
+    const name = try std.fmt.allocPrint(&ctx.arena.allocator, "arg{d}", .{ctx.argdex});
     ctx.argdex += 1;
     return name;
 }
@@ -528,7 +528,7 @@ fn genCall(ctx: *Context, file: *C, inst: *Inst.Call) !?[]u8 {
                     try renderValue(ctx, writer, arg.ty, val);
                 } else {
                     const val = try ctx.resolveInst(arg);
-                    try writer.print("{}", .{val});
+                    try writer.print("{s}", .{val});
                 }
             }
         }
diff --git a/src/glibc.zig b/src/glibc.zig
index f69dd11ada..e7b7b1b1cf 100644
--- a/src/glibc.zig
+++ b/src/glibc.zig
@@ -111,12 +111,12 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
         while (it.next()) |line| : (line_i += 1) {
             const prefix = "GLIBC_";
             if (!mem.startsWith(u8, line, prefix)) {
-                std.log.err("vers.txt:{}: expected 'GLIBC_' prefix", .{line_i});
+                std.log.err("vers.txt:{d}: expected 'GLIBC_' prefix", .{line_i});
                 return error.ZigInstallationCorrupt;
             }
             const adjusted_line = line[prefix.len..];
             const ver = std.builtin.Version.parse(adjusted_line) catch |err| {
-                std.log.err("vers.txt:{}: unable to parse glibc version '{s}': {s}", .{ line_i, line, @errorName(err) });
+                std.log.err("vers.txt:{d}: unable to parse glibc version '{s}': {s}", .{ line_i, line, @errorName(err) });
                 return error.ZigInstallationCorrupt;
             };
             try all_versions.append(arena, ver);
@@ -128,15 +128,15 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
         while (file_it.next()) |line| : (line_i += 1) {
             var line_it = mem.tokenize(line, " ");
             const fn_name = line_it.next() orelse {
-                std.log.err("fns.txt:{}: expected function name", .{line_i});
+                std.log.err("fns.txt:{d}: expected function name", .{line_i});
                 return error.ZigInstallationCorrupt;
             };
             const lib_name = line_it.next() orelse {
-                std.log.err("fns.txt:{}: expected library name", .{line_i});
+                std.log.err("fns.txt:{d}: expected library name", .{line_i});
                 return error.ZigInstallationCorrupt;
             };
             const lib = findLib(lib_name) orelse {
-                std.log.err("fns.txt:{}: unknown library name: {s}", .{ line_i, lib_name });
+                std.log.err("fns.txt:{d}: unknown library name: {s}", .{ line_i, lib_name });
                 return error.ZigInstallationCorrupt;
             };
             try all_functions.append(arena, .{
@@ -158,27 +158,27 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
                 while (line_it.next()) |target_string| {
                     var component_it = mem.tokenize(target_string, "-");
                     const arch_name = component_it.next() orelse {
-                        std.log.err("abi.txt:{}: expected arch name", .{line_i});
+                        std.log.err("abi.txt:{d}: expected arch name", .{line_i});
                         return error.ZigInstallationCorrupt;
                     };
                     const os_name = component_it.next() orelse {
-                        std.log.err("abi.txt:{}: expected OS name", .{line_i});
+                        std.log.err("abi.txt:{d}: expected OS name", .{line_i});
                         return error.ZigInstallationCorrupt;
                     };
                     const abi_name = component_it.next() orelse {
-                        std.log.err("abi.txt:{}: expected ABI name", .{line_i});
+                        std.log.err("abi.txt:{d}: expected ABI name", .{line_i});
                         return error.ZigInstallationCorrupt;
                     };
                     const arch_tag = std.meta.stringToEnum(std.Target.Cpu.Arch, arch_name) orelse {
-                        std.log.err("abi.txt:{}: unrecognized arch: '{s}'", .{ line_i, arch_name });
+                        std.log.err("abi.txt:{d}: unrecognized arch: '{s}'", .{ line_i, arch_name });
                         return error.ZigInstallationCorrupt;
                     };
                     if (!mem.eql(u8, os_name, "linux")) {
-                        std.log.err("abi.txt:{}: expected OS 'linux', found '{s}'", .{ line_i, os_name });
+                        std.log.err("abi.txt:{d}: expected OS 'linux', found '{s}'", .{ line_i, os_name });
                         return error.ZigInstallationCorrupt;
                     }
                     const abi_tag = std.meta.stringToEnum(std.Target.Abi, abi_name) orelse {
-                        std.log.err("abi.txt:{}: unrecognized ABI: '{s}'", .{ line_i, abi_name });
+                        std.log.err("abi.txt:{d}: unrecognized ABI: '{s}'", .{ line_i, abi_name });
                         return error.ZigInstallationCorrupt;
                     };
 
@@ -193,7 +193,7 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
             };
             for (ver_list_base) |*ver_list| {
                 const line = file_it.next() orelse {
-                    std.log.err("abi.txt:{}: missing version number line", .{line_i});
+                    std.log.err("abi.txt:{d}: missing version number line", .{line_i});
                     return error.ZigInstallationCorrupt;
                 };
                 line_i += 1;
@@ -206,12 +206,12 @@ pub fn loadMetaData(gpa: *Allocator, zig_lib_dir: std.fs.Dir) LoadMetaDataError!
                 while (line_it.next()) |version_index_string| {
                     if (ver_list.len >= ver_list.versions.len) {
                         // If this happens with legit data, increase the array len in the type.
-                        std.log.err("abi.txt:{}: too many versions", .{line_i});
+                        std.log.err("abi.txt:{d}: too many versions", .{line_i});
                         return error.ZigInstallationCorrupt;
                     }
                     const version_index = std.fmt.parseInt(u8, version_index_string, 10) catch |err| {
                         // If this happens with legit data, increase the size of the integer type in the struct.
-                        std.log.err("abi.txt:{}: unable to parse version: {s}", .{ line_i, @errorName(err) });
+                        std.log.err("abi.txt:{d}: unable to parse version: {s}", .{ line_i, @errorName(err) });
                         return error.ZigInstallationCorrupt;
                     };
 
diff --git a/src/link.zig b/src/link.zig
index 92702c7973..3dbfb3b922 100644
--- a/src/link.zig
+++ b/src/link.zig
@@ -523,7 +523,7 @@ pub const File = struct {
                 id_symlink_basename,
                 &prev_digest_buf,
             ) catch |err| b: {
-                log.debug("archive new_digest={} readFile error: {}", .{ digest, @errorName(err) });
+                log.debug("archive new_digest={} readFile error: {s}", .{ digest, @errorName(err) });
                 break :b prev_digest_buf[0..0];
             };
             if (mem.eql(u8, prev_digest, &digest)) {
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 5d0e897008..116d7c9859 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -2082,10 +2082,10 @@ pub fn allocateDeclIndexes(self: *Elf, decl: *Module.Decl) !void {
     try self.offset_table.ensureCapacity(self.base.allocator, self.offset_table.items.len + 1);
 
     if (self.local_symbol_free_list.popOrNull()) |i| {
-        log.debug("reusing symbol index {} for {s}\n", .{ i, decl.name });
+        log.debug("reusing symbol index {d} for {s}\n", .{ i, decl.name });
         decl.link.elf.local_sym_index = i;
     } else {
-        log.debug("allocating symbol index {} for {s}\n", .{ self.local_symbols.items.len, decl.name });
+        log.debug("allocating symbol index {d} for {s}\n", .{ self.local_symbols.items.len, decl.name });
         decl.link.elf.local_sym_index = @intCast(u32, self.local_symbols.items.len);
         _ = self.local_symbols.addOneAssumeCapacity();
     }
@@ -2432,7 +2432,7 @@ pub fn updateDecl(self: *Elf, module: *Module, decl: *Module.Decl) !void {
             if (needed_size > self.allocatedSize(debug_line_sect.sh_offset)) {
                 const new_offset = self.findFreeSpace(needed_size, 1);
                 const existing_size = last_src_fn.off;
-                log.debug("moving .debug_line section: {} bytes from 0x{x} to 0x{x}\n", .{
+                log.debug("moving .debug_line section: {d} bytes from 0x{x} to 0x{x}\n", .{
                     existing_size,
                     debug_line_sect.sh_offset,
                     new_offset,
diff --git a/src/liveness.zig b/src/liveness.zig
index 0d759f8312..b0aafa28f1 100644
--- a/src/liveness.zig
+++ b/src/liveness.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 const ir = @import("ir.zig");
 const trace = @import("tracy.zig").trace;
+const log = std.log.scoped(.liveness);
 
 /// Perform Liveness Analysis over the `Body`. Each `Inst` will have its `deaths` field populated.
 pub fn analyze(
@@ -248,5 +249,5 @@ fn analyzeInst(
         @panic("Handle liveness analysis for instructions with many parameters");
     }
 
-    std.log.scoped(.liveness).debug("analyze {}: 0b{b}\n", .{ base.tag, base.deaths });
+    log.debug("analyze {}: 0b{b}\n", .{ base.tag, base.deaths });
 }
diff --git a/src/main.zig b/src/main.zig
index 7d03ea956f..b1243badff 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -626,7 +626,7 @@ fn buildOutputType(
                             fs.path.dirname(pkg_path),
                             fs.path.basename(pkg_path),
                         ) catch |err| {
-                            fatal("Failed to add package at path {}: {}", .{ pkg_path, @errorName(err) });
+                            fatal("Failed to add package at path {s}: {s}", .{ pkg_path, @errorName(err) });
                         };
                         new_cur_pkg.parent = cur_pkg;
                         try cur_pkg.add(gpa, pkg_name, new_cur_pkg);
@@ -696,13 +696,13 @@ fn buildOutputType(
                         if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         stack_size_override = std.fmt.parseUnsigned(u64, args[i], 0) catch |err| {
-                            fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                            fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                         };
                     } else if (mem.eql(u8, arg, "--image-base")) {
                         if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
                         i += 1;
                         image_base_override = std.fmt.parseUnsigned(u64, args[i], 0) catch |err| {
-                            fatal("unable to parse '{}': {}", .{ arg, @errorName(err) });
+                            fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
                         };
                     } else if (mem.eql(u8, arg, "--name")) {
                         if (i + 1 >= args.len) fatal("expected parameter after {s}", .{arg});
@@ -1914,7 +1914,7 @@ fn buildOutputType(
                                 if (!watch) return cleanExit();
                             } else {
                                 const cmd = try argvCmd(arena, argv.items);
-                                fatal("the following test command failed with exit code {}:\n{s}", .{ code, cmd });
+                                fatal("the following test command failed with exit code {d}:\n{s}", .{ code, cmd });
                             }
                         },
                         else => {
@@ -2069,7 +2069,7 @@ fn cmdTranslateC(comp: *Compilation, arena: *Allocator, enable_cache: bool) !voi
             error.ASTUnitFailure => fatal("clang API returned errors but due to a clang bug, it is not exposing the errors for zig to see. For more details: https://github.com/ziglang/zig/issues/4455", .{}),
             error.SemanticAnalyzeFail => {
                 for (clang_errors) |clang_err| {
-                    std.debug.print("{s}:{}:{}: {s}\n", .{
+                    std.debug.print("{s}:{d}:{d}: {s}\n", .{
                         if (clang_err.filename_ptr) |p| p[0..clang_err.filename_len] else "(no file)",
                         clang_err.line + 1,
                         clang_err.column + 1,
@@ -2493,7 +2493,7 @@ pub fn cmdBuild(gpa: *Allocator, arena: *Allocator, args: []const []const u8) !v
         .Exited => |code| {
             if (code == 0) return cleanExit();
             const cmd = try argvCmd(arena, child_argv);
-            fatal("the following build command failed with exit code {}:\n{s}", .{ code, cmd });
+            fatal("the following build command failed with exit code {d}:\n{s}", .{ code, cmd });
         },
         else => {
             const cmd = try argvCmd(arena, child_argv);
@@ -2812,7 +2812,7 @@ fn printErrMsgToFile(
     const text = text_buf.items;
 
     const stream = file.outStream();
-    try stream.print("{s}:{}:{}: error: {s}\n", .{ path, start_loc.line + 1, start_loc.column + 1, text });
+    try stream.print("{s}:{d}:{d}: error: {s}\n", .{ path, start_loc.line + 1, start_loc.column + 1, text });
 
     if (!color_on) return;
 
diff --git a/src/translate_c.zig b/src/translate_c.zig
index c609597770..1b6455fd4d 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -136,7 +136,7 @@ const Scope = struct {
             var proposed_name = name_copy;
             while (scope.contains(proposed_name)) {
                 scope.mangle_count += 1;
-                proposed_name = try std.fmt.allocPrint(c.arena, "{s}_{}", .{ name, scope.mangle_count });
+                proposed_name = try std.fmt.allocPrint(c.arena, "{s}_{d}", .{ name, scope.mangle_count });
             }
             try scope.variables.append(.{ .name = name_copy, .alias = proposed_name });
             return proposed_name;
@@ -440,7 +440,7 @@ pub fn translate(
     mem.copy(*ast.Node, root_node.decls(), context.root_decls.items);
 
     if (false) {
-        std.debug.warn("debug source:\n{}\n==EOF==\ntokens:\n", .{source_buffer.items});
+        std.debug.warn("debug source:\n{s}\n==EOF==\ntokens:\n", .{source_buffer.items});
         for (context.token_ids.items) |token| {
             std.debug.warn("{}\n", .{token});
         }
@@ -945,7 +945,7 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
     // Record declarations such as `struct {...} x` have no name but they're not
     // anonymous hence here isAnonymousStructOrUnion is not needed
     if (bare_name.len == 0) {
-        bare_name = try std.fmt.allocPrint(c.arena, "unnamed_{}", .{c.getMangle()});
+        bare_name = try std.fmt.allocPrint(c.arena, "unnamed_{d}", .{c.getMangle()});
         is_unnamed = true;
     }
 
@@ -1019,7 +1019,7 @@ fn transRecordDecl(c: *Context, record_decl: *const clang.RecordDecl) Error!?*as
             var raw_name = try c.str(@ptrCast(*const clang.NamedDecl, field_decl).getName_bytes_begin());
             if (field_decl.isAnonymousStructOrUnion() or raw_name.len == 0) {
                 // Context.getMangle() is not used here because doing so causes unpredictable field names for anonymous fields.
-                raw_name = try std.fmt.allocPrint(c.arena, "unnamed_{}", .{unnamed_field_count});
+                raw_name = try std.fmt.allocPrint(c.arena, "unnamed_{d}", .{unnamed_field_count});
                 unnamed_field_count += 1;
                 is_anon = true;
             }
@@ -1110,7 +1110,7 @@ fn transEnumDecl(c: *Context, enum_decl: *const clang.EnumDecl) Error!?*ast.Node
     var bare_name = try c.str(@ptrCast(*const clang.NamedDecl, enum_decl).getName_bytes_begin());
     var is_unnamed = false;
     if (bare_name.len == 0) {
-        bare_name = try std.fmt.allocPrint(c.arena, "unnamed_{}", .{c.getMangle()});
+        bare_name = try std.fmt.allocPrint(c.arena, "unnamed_{d}", .{c.getMangle()});
         is_unnamed = true;
     }
 
@@ -3956,7 +3956,7 @@ fn qualTypeToLog2IntRef(rp: RestorePoint, qt: clang.QualType, source_loc: clang.
         const node = try rp.c.arena.create(ast.Node.OneToken);
         node.* = .{
             .base = .{ .tag = .IntegerLiteral },
-            .token = try appendTokenFmt(rp.c, .Identifier, "u{}", .{cast_bit_width}),
+            .token = try appendTokenFmt(rp.c, .Identifier, "u{d}", .{cast_bit_width}),
         };
         return &node.base;
     }
@@ -4484,7 +4484,7 @@ fn transCreateNodeMacroFn(c: *Context, name: []const u8, ref: *ast.Node, proto_a
             _ = try appendToken(c, .Comma, ",");
         }
         const param_name_tok = param.name_token orelse
-            try appendTokenFmt(c, .Identifier, "arg_{}", .{c.getMangle()});
+            try appendTokenFmt(c, .Identifier, "arg_{d}", .{c.getMangle()});
 
         _ = try appendToken(c, .Colon, ":");
 
@@ -5916,11 +5916,11 @@ fn parseCPrimaryExprInner(c: *Context, m: *MacroCtx, scope: *Scope) ParseError!*
             // struct Foo will be declared as struct_Foo by transRecordDecl
             const next_id = m.next().?;
             if (next_id != .Identifier) {
-                try m.fail(c, "unable to translate C expr: expected Identifier instead got: {}", .{@tagName(next_id)});
+                try m.fail(c, "unable to translate C expr: expected Identifier instead got: {s}", .{@tagName(next_id)});
                 return error.ParseError;
             }
 
-            const ident_token = try appendTokenFmt(c, .Identifier, "{}_{}", .{ slice, m.slice() });
+            const ident_token = try appendTokenFmt(c, .Identifier, "{s}_{s}", .{ slice, m.slice() });
             const identifier = try c.arena.create(ast.Node.OneToken);
             identifier.* = .{
                 .base = .{ .tag = .Identifier },
diff --git a/src/type.zig b/src/type.zig
index bb2e3b3bc2..9e2cd321f0 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -558,21 +558,21 @@ pub const Type = extern union {
                 },
                 .array_u8 => {
                     const len = ty.castTag(.array_u8).?.data;
-                    return out_stream.print("[{}]u8", .{len});
+                    return out_stream.print("[{d}]u8", .{len});
                 },
                 .array_u8_sentinel_0 => {
                     const len = ty.castTag(.array_u8_sentinel_0).?.data;
-                    return out_stream.print("[{}:0]u8", .{len});
+                    return out_stream.print("[{d}:0]u8", .{len});
                 },
                 .array => {
                     const payload = ty.castTag(.array).?.data;
-                    try out_stream.print("[{}]", .{payload.len});
+                    try out_stream.print("[{d}]", .{payload.len});
                     ty = payload.elem_type;
                     continue;
                 },
                 .array_sentinel => {
                     const payload = ty.castTag(.array_sentinel).?.data;
-                    try out_stream.print("[{}:{}]", .{ payload.len, payload.sentinel });
+                    try out_stream.print("[{d}:{}]", .{ payload.len, payload.sentinel });
                     ty = payload.elem_type;
                     continue;
                 },
diff --git a/src/zir.zig b/src/zir.zig
index 94e2b24b0c..0593cbd8fd 100644
--- a/src/zir.zig
+++ b/src/zir.zig
@@ -1257,12 +1257,12 @@ const Writer = struct {
                     self.next_instr_index += 1;
                     try self.inst_table.putNoClobber(inst, .{ .inst = inst, .index = my_i, .name = undefined });
                     try stream.writeByteNTimes(' ', self.indent);
-                    try stream.print("%{} ", .{my_i});
+                    try stream.print("%{d} ", .{my_i});
                     if (inst.cast(Inst.Block)) |block| {
-                        const name = try std.fmt.allocPrint(&self.arena.allocator, "label_{}", .{my_i});
+                        const name = try std.fmt.allocPrint(&self.arena.allocator, "label_{d}", .{my_i});
                         try self.block_table.put(block, name);
                     } else if (inst.cast(Inst.Loop)) |loop| {
-                        const name = try std.fmt.allocPrint(&self.arena.allocator, "loop_{}", .{my_i});
+                        const name = try std.fmt.allocPrint(&self.arena.allocator, "loop_{d}", .{my_i});
                         try self.loop_table.put(loop, name);
                     }
                     self.indent += 2;
@@ -1332,7 +1332,7 @@ const Writer = struct {
     fn writeInstParamToStream(self: *Writer, stream: anytype, inst: *Inst) !void {
         if (self.inst_table.get(inst)) |info| {
             if (info.index) |i| {
-                try stream.print("%{}", .{info.index});
+                try stream.print("%{d}", .{info.index});
             } else {
                 try stream.print("@{s}", .{info.name});
             }
@@ -1660,7 +1660,6 @@ const Parser = struct {
             .contents_hash = std.zig.hashSrc(self.source[contents_start..self.i]),
             .inst = &inst_specific.base,
         };
-        //std.debug.warn("parsed {} = '{}'\n", .{ inst_specific.base.name, inst_specific.base.contents });
 
         return decl;
     }
@@ -1805,7 +1804,7 @@ const Parser = struct {
     }
 
     fn generateName(self: *Parser) ![]u8 {
-        const result = try std.fmt.allocPrint(&self.arena.allocator, "unnamed${}", .{self.unnamed_index});
+        const result = try std.fmt.allocPrint(&self.arena.allocator, "unnamed${d}", .{self.unnamed_index});
         self.unnamed_index += 1;
         return result;
     }
@@ -2865,7 +2864,7 @@ const EmitZIR = struct {
 
     fn autoName(self: *EmitZIR) ![]u8 {
         while (true) {
-            const proposed_name = try std.fmt.allocPrint(&self.arena.allocator, "unnamed${}", .{self.next_auto_name});
+            const proposed_name = try std.fmt.allocPrint(&self.arena.allocator, "unnamed${d}", .{self.next_auto_name});
             self.next_auto_name += 1;
             const gop = try self.names.getOrPut(proposed_name);
             if (!gop.found_existing) {
@@ -2954,15 +2953,15 @@ pub fn dumpZir(allocator: *Allocator, kind: []const u8, decl_name: [*:0]const u8
         write.next_instr_index += 1;
 
         if (inst.cast(Inst.Block)) |block| {
-            const name = try std.fmt.allocPrint(&write.arena.allocator, "label_{}", .{my_i});
+            const name = try std.fmt.allocPrint(&write.arena.allocator, "label_{d}", .{my_i});
             try write.block_table.put(block, name);
         } else if (inst.cast(Inst.Loop)) |loop| {
-            const name = try std.fmt.allocPrint(&write.arena.allocator, "loop_{}", .{my_i});
+            const name = try std.fmt.allocPrint(&write.arena.allocator, "loop_{d}", .{my_i});
             try write.loop_table.put(loop, name);
         }
 
         try write.inst_table.putNoClobber(inst, .{ .inst = inst, .index = my_i, .name = "inst" });
-        try stderr.print("  %{} ", .{my_i});
+        try stderr.print("  %{d} ", .{my_i});
         try write.writeInstToStream(stderr, inst);
         try stderr.writeByte('\n');
     }
diff --git a/src/zir_sema.zig b/src/zir_sema.zig
index 72a1b04238..f9cd0e1a3d 100644
--- a/src/zir_sema.zig
+++ b/src/zir_sema.zig
@@ -535,7 +535,7 @@ fn analyzeInstParamType(mod: *Module, scope: *Scope, inst: *zir.Inst.ParamType)
     // TODO support C-style var args
     const param_count = fn_ty.fnParamLen();
     if (arg_index >= param_count) {
-        return mod.fail(scope, inst.base.src, "arg index {} out of bounds; '{}' has {} argument(s)", .{
+        return mod.fail(scope, inst.base.src, "arg index {d} out of bounds; '{}' has {d} argument(s)", .{
             arg_index,
             fn_ty,
             param_count,
@@ -580,7 +580,7 @@ fn analyzeInstArg(mod: *Module, scope: *Scope, inst: *zir.Inst.Arg) InnerError!*
     const param_index = b.instructions.items.len;
     const param_count = fn_ty.fnParamLen();
     if (param_index >= param_count) {
-        return mod.fail(scope, inst.base.src, "parameter index {} outside list of length {}", .{
+        return mod.fail(scope, inst.base.src, "parameter index {d} outside list of length {d}", .{
             param_index,
             param_count,
         });
@@ -790,7 +790,7 @@ fn analyzeInstCall(mod: *Module, scope: *Scope, inst: *zir.Inst.Call) InnerError
             return mod.fail(
                 scope,
                 inst.positionals.func.src,
-                "expected at least {} argument(s), found {}",
+                "expected at least {d} argument(s), found {d}",
                 .{ fn_params_len, call_params_len },
             );
         }
@@ -800,7 +800,7 @@ fn analyzeInstCall(mod: *Module, scope: *Scope, inst: *zir.Inst.Call) InnerError
         return mod.fail(
             scope,
             inst.positionals.func.src,
-            "expected {} argument(s), found {}",
+            "expected {d} argument(s), found {d}",
             .{ fn_params_len, call_params_len },
         );
     }
@@ -1545,7 +1545,7 @@ fn analyzeInstBitwise(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) InnerE
 
     if (lhs.ty.zigTypeTag() == .Vector and rhs.ty.zigTypeTag() == .Vector) {
         if (lhs.ty.arrayLen() != rhs.ty.arrayLen()) {
-            return mod.fail(scope, inst.base.src, "vector length mismatch: {} and {}", .{
+            return mod.fail(scope, inst.base.src, "vector length mismatch: {d} and {d}", .{
                 lhs.ty.arrayLen(),
                 rhs.ty.arrayLen(),
             });
@@ -1620,7 +1620,7 @@ fn analyzeInstArithmetic(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) Inn
 
     if (lhs.ty.zigTypeTag() == .Vector and rhs.ty.zigTypeTag() == .Vector) {
         if (lhs.ty.arrayLen() != rhs.ty.arrayLen()) {
-            return mod.fail(scope, inst.base.src, "vector length mismatch: {} and {}", .{
+            return mod.fail(scope, inst.base.src, "vector length mismatch: {d} and {d}", .{
                 lhs.ty.arrayLen(),
                 rhs.ty.arrayLen(),
             });
@@ -1791,7 +1791,7 @@ fn analyzeInstCmp(
         return mod.cmpNumeric(scope, inst.base.src, lhs, rhs, op);
     } else if (lhs_ty_tag == .Type and rhs_ty_tag == .Type) {
         if (!is_equality_cmp) {
-            return mod.fail(scope, inst.base.src, "{} operator not allowed for types", .{@tagName(op)});
+            return mod.fail(scope, inst.base.src, "{s} operator not allowed for types", .{@tagName(op)});
         }
         return mod.constBool(scope, inst.base.src, lhs.value().?.eql(rhs.value().?) == (op == .eq));
     }