Merge pull request #4324 from fengb/testing-allocator

Remove debug.global_allocator in favor of testing.allocator

doc/docgen.zig

@@ -672,7 +672,8 @@ const TermState = enum {
 
 test "term color" {
     const input_bytes = "A\x1b[32;1mgreen\x1b[0mB";
-    const result = try termColor(std.debug.global_allocator, input_bytes);
+    const result = try termColor(std.testing.allocator, input_bytes);
+    defer std.testing.allocator.free(result);
     testing.expectEqualSlices(u8, "A<span class=\"t32\">green</span>B", result);
 }
 

doc/langref.html.in

@@ -5359,7 +5359,7 @@ const std = @import("std");
 const assert = std.debug.assert;
 
 test "turn HashMap into a set with void" {
-    var map = std.HashMap(i32, void, hash_i32, eql_i32).init(std.debug.global_allocator);
+    var map = std.HashMap(i32, void, hash_i32, eql_i32).init(std.testing.allocator);
     defer map.deinit();
 
     _ = try map.put(1, {});
@@ -9281,9 +9281,8 @@ fn concat(allocator: *Allocator, a: []const u8, b: []const u8) ![]u8 {
       In the above example, 100 bytes of stack memory are used to initialize a
       {#syntax#}FixedBufferAllocator{#endsyntax#}, which is then passed to a function.
       As a convenience there is a global {#syntax#}FixedBufferAllocator{#endsyntax#}
-      available for quick tests at {#syntax#}std.debug.global_allocator{#endsyntax#},
+      available for quick tests at {#syntax#}std.testing.allocator{#endsyntax#},
-      however it is deprecated and should be avoided in favor of directly using a
+      which will also do perform basic leak detection.
-      {#syntax#}FixedBufferAllocator{#endsyntax#} as in the example above.
       </p>
       <p>
       Currently Zig has no general purpose allocator, but there is
@@ -9341,7 +9340,7 @@ pub fn main() !void {
           </li>
           <li>
               Are you writing a test, and you want to make sure {#syntax#}error.OutOfMemory{#endsyntax#}
-              is handled correctly? In this case, use {#syntax#}std.debug.FailingAllocator{#endsyntax#}.
+              is handled correctly? In this case, use {#syntax#}std.testing.FailingAllocator{#endsyntax#}.
           </li>
           <li>
               Finally, if none of the above apply, you need a general purpose allocator. Zig does not

lib/std/array_list.zig

@@ -320,7 +320,7 @@ test "std.ArrayList.basic" {
 }
 
 test "std.ArrayList.orderedRemove" {
-    var list = ArrayList(i32).init(debug.global_allocator);
+    var list = ArrayList(i32).init(testing.allocator);
     defer list.deinit();
 
     try list.append(1);
@@ -347,7 +347,7 @@ test "std.ArrayList.orderedRemove" {
 }
 
 test "std.ArrayList.swapRemove" {
-    var list = ArrayList(i32).init(debug.global_allocator);
+    var list = ArrayList(i32).init(testing.allocator);
     defer list.deinit();
 
     try list.append(1);
@@ -374,7 +374,7 @@ test "std.ArrayList.swapRemove" {
 }
 
 test "std.ArrayList.swapRemoveOrError" {
-    var list = ArrayList(i32).init(debug.global_allocator);
+    var list = ArrayList(i32).init(testing.allocator);
     defer list.deinit();
 
     // Test just after initialization
@@ -402,7 +402,7 @@ test "std.ArrayList.swapRemoveOrError" {
 }
 
 test "std.ArrayList.insert" {
-    var list = ArrayList(i32).init(debug.global_allocator);
+    var list = ArrayList(i32).init(testing.allocator);
     defer list.deinit();
 
     try list.append(1);
@@ -416,7 +416,7 @@ test "std.ArrayList.insert" {
 }
 
 test "std.ArrayList.insertSlice" {
-    var list = ArrayList(i32).init(debug.global_allocator);
+    var list = ArrayList(i32).init(testing.allocator);
     defer list.deinit();
 
     try list.append(1);
@@ -443,7 +443,8 @@ const Item = struct {
 };
 
 test "std.ArrayList: ArrayList(T) of struct T" {
-    var root = Item{ .integer = 1, .sub_items = ArrayList(Item).init(debug.global_allocator) };
+    var root = Item{ .integer = 1, .sub_items = ArrayList(Item).init(testing.allocator) };
-    try root.sub_items.append(Item{ .integer = 42, .sub_items = ArrayList(Item).init(debug.global_allocator) });
+    defer root.sub_items.deinit();
+    try root.sub_items.append(Item{ .integer = 42, .sub_items = ArrayList(Item).init(testing.allocator) });
     testing.expect(root.sub_items.items[0].integer == 42);
 }

lib/std/buf_map.zig

@@ -43,9 +43,10 @@ pub const BufMap = struct {
     pub fn set(self: *BufMap, key: []const u8, value: []const u8) !void {
         const value_copy = try self.copy(value);
         errdefer self.free(value_copy);
-        // Avoid copying key if it already exists
         const get_or_put = try self.hash_map.getOrPut(key);
-        if (!get_or_put.found_existing) {
+        if (get_or_put.found_existing) {
+            self.free(get_or_put.kv.value);
+        } else {
             get_or_put.kv.key = self.copy(key) catch |err| {
                 _ = self.hash_map.remove(key);
                 return err;
@@ -83,7 +84,7 @@ pub const BufMap = struct {
 };
 
 test "BufMap" {
-    var bufmap = BufMap.init(std.heap.page_allocator);
+    var bufmap = BufMap.init(std.testing.allocator);
     defer bufmap.deinit();
 
     try bufmap.set("x", "1");

lib/std/buf_set.zig

@@ -65,7 +65,7 @@ pub const BufSet = struct {
 };
 
 test "BufSet" {
-    var bufset = BufSet.init(std.heap.page_allocator);
+    var bufset = BufSet.init(std.testing.allocator);
     defer bufset.deinit();
 
     try bufset.put("x");

lib/std/buffer.zig

@@ -150,7 +150,9 @@ pub const Buffer = struct {
 };
 
 test "simple Buffer" {
-    var buf = try Buffer.init(debug.global_allocator, "");
+    var buf = try Buffer.init(testing.allocator, "");
+    defer buf.deinit();
+
     testing.expect(buf.len() == 0);
     try buf.append("hello");
     try buf.append(" ");
@@ -159,6 +161,7 @@ test "simple Buffer" {
     testing.expect(mem.eql(u8, mem.toSliceConst(u8, buf.toSliceConst().ptr), buf.toSliceConst()));
 
     var buf2 = try Buffer.initFromBuffer(buf);
+    defer buf2.deinit();
     testing.expect(buf.eql(buf2.toSliceConst()));
 
     testing.expect(buf.startsWith("hell"));
@@ -169,14 +172,16 @@ test "simple Buffer" {
 }
 
 test "Buffer.initSize" {
-    var buf = try Buffer.initSize(debug.global_allocator, 3);
+    var buf = try Buffer.initSize(testing.allocator, 3);
+    defer buf.deinit();
     testing.expect(buf.len() == 3);
     try buf.append("hello");
     testing.expect(mem.eql(u8, buf.toSliceConst()[3..], "hello"));
 }
 
 test "Buffer.initCapacity" {
-    var buf = try Buffer.initCapacity(debug.global_allocator, 10);
+    var buf = try Buffer.initCapacity(testing.allocator, 10);
+    defer buf.deinit();
     testing.expect(buf.len() == 0);
     testing.expect(buf.capacity() >= 10);
     const old_cap = buf.capacity();

lib/std/build.zig

@@ -1059,7 +1059,10 @@ pub const Builder = struct {
 };
 
 test "builder.findProgram compiles" {
+    // TODO: uncomment and fix the leak
+    // const builder = try Builder.create(std.testing.allocator, "zig", "zig-cache", "zig-cache");
     const builder = try Builder.create(std.heap.page_allocator, "zig", "zig-cache", "zig-cache");
+    defer builder.destroy();
     _ = builder.findProgram(&[_][]const u8{}, &[_][]const u8{}) catch null;
 }
 

lib/std/debug.zig

@@ -19,8 +19,8 @@ const windows = std.os.windows;
 
 pub const leb = @import("debug/leb128.zig");
 
-pub const FailingAllocator = @import("debug/failing_allocator.zig").FailingAllocator;
+pub const global_allocator = @compileError("Please switch to std.testing.allocator.");
-pub const failing_allocator = &FailingAllocator.init(global_allocator, 0).allocator;
+pub const failing_allocator = @compileError("Please switch to std.testing.failing_allocator.");
 
 pub const runtime_safety = switch (builtin.mode) {
     .Debug, .ReleaseSafe => true,
@@ -2196,11 +2196,6 @@ fn readInitialLength(comptime E: type, in_stream: *io.InStream(E), is_64: *bool)
     }
 }
 
-/// This should only be used in temporary test programs.
-pub const global_allocator = &global_fixed_allocator.allocator;
-var global_fixed_allocator = std.heap.ThreadSafeFixedBufferAllocator.init(global_allocator_mem[0..]);
-var global_allocator_mem: [100 * 1024]u8 = undefined;
-
 /// TODO multithreaded awareness
 var debug_info_allocator: ?*mem.Allocator = null;
 var debug_info_arena_allocator: std.heap.ArenaAllocator = undefined;

lib/std/fifo.zig

@@ -347,7 +347,7 @@ pub fn LinearFifo(
 }
 
 test "LinearFifo(u8, .Dynamic)" {
-    var fifo = LinearFifo(u8, .Dynamic).init(debug.global_allocator);
+    var fifo = LinearFifo(u8, .Dynamic).init(testing.allocator);
     defer fifo.deinit();
 
     try fifo.write("HELLO");
@@ -422,7 +422,7 @@ test "LinearFifo" {
             var fifo = switch (bt) {
                 .Static => FifoType.init(),
                 .Slice => FifoType.init(buf[0..]),
-                .Dynamic => FifoType.init(debug.global_allocator),
+                .Dynamic => FifoType.init(testing.allocator),
             };
             defer fifo.deinit();
 

lib/std/fmt.zig

@@ -1598,7 +1598,8 @@ test "hexToBytes" {
 test "formatIntValue with comptime_int" {
     const value: comptime_int = 123456789123456789;
 
-    var buf = try std.Buffer.init(std.debug.global_allocator, "");
+    var buf = try std.Buffer.init(std.testing.allocator, "");
+    defer buf.deinit();
     try formatIntValue(value, "", FormatOptions{}, &buf, @TypeOf(std.Buffer.append).ReturnType.ErrorSet, std.Buffer.append);
     std.testing.expect(mem.eql(u8, buf.toSlice(), "123456789123456789"));
 }
@@ -1652,19 +1653,23 @@ test "formatType max_depth" {
     inst.a = &inst;
     inst.tu.ptr = &inst.tu;
 
-    var buf0 = try std.Buffer.init(std.debug.global_allocator, "");
+    var buf0 = try std.Buffer.init(std.testing.allocator, "");
+    defer buf0.deinit();
     try formatType(inst, "", FormatOptions{}, &buf0, @TypeOf(std.Buffer.append).ReturnType.ErrorSet, std.Buffer.append, 0);
     std.testing.expect(mem.eql(u8, buf0.toSlice(), "S{ ... }"));
 
-    var buf1 = try std.Buffer.init(std.debug.global_allocator, "");
+    var buf1 = try std.Buffer.init(std.testing.allocator, "");
+    defer buf1.deinit();
     try formatType(inst, "", FormatOptions{}, &buf1, @TypeOf(std.Buffer.append).ReturnType.ErrorSet, std.Buffer.append, 1);
     std.testing.expect(mem.eql(u8, buf1.toSlice(), "S{ .a = S{ ... }, .tu = TU{ ... }, .e = E.Two, .vec = (10.200,2.220) }"));
 
-    var buf2 = try std.Buffer.init(std.debug.global_allocator, "");
+    var buf2 = try std.Buffer.init(std.testing.allocator, "");
+    defer buf2.deinit();
     try formatType(inst, "", FormatOptions{}, &buf2, @TypeOf(std.Buffer.append).ReturnType.ErrorSet, std.Buffer.append, 2);
     std.testing.expect(mem.eql(u8, buf2.toSlice(), "S{ .a = S{ .a = S{ ... }, .tu = TU{ ... }, .e = E.Two, .vec = (10.200,2.220) }, .tu = TU{ .ptr = TU{ ... } }, .e = E.Two, .vec = (10.200,2.220) }"));
 
-    var buf3 = try std.Buffer.init(std.debug.global_allocator, "");
+    var buf3 = try std.Buffer.init(std.testing.allocator, "");
+    defer buf3.deinit();
     try formatType(inst, "", FormatOptions{}, &buf3, @TypeOf(std.Buffer.append).ReturnType.ErrorSet, std.Buffer.append, 3);
     std.testing.expect(mem.eql(u8, buf3.toSlice(), "S{ .a = S{ .a = S{ .a = S{ ... }, .tu = TU{ ... }, .e = E.Two, .vec = (10.200,2.220) }, .tu = TU{ .ptr = TU{ ... } }, .e = E.Two, .vec = (10.200,2.220) }, .tu = TU{ .ptr = TU{ .ptr = TU{ ... } } }, .e = E.Two, .vec = (10.200,2.220) }"));
 }

lib/std/fs/path.zig

@@ -665,15 +665,16 @@ pub fn resolvePosix(allocator: *Allocator, paths: []const []const u8) ![]u8 {
 }
 
 test "resolve" {
-    const cwd = try process.getCwdAlloc(debug.global_allocator);
+    const cwd = try process.getCwdAlloc(testing.allocator);
+    defer testing.allocator.free(cwd);
     if (builtin.os == .windows) {
         if (windowsParsePath(cwd).kind == WindowsPath.Kind.Drive) {
             cwd[0] = asciiUpper(cwd[0]);
         }
-        testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{"."}), cwd));
+        try testResolveWindows(&[_][]const u8{"."}, cwd);
     } else {
-        testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "a/b/c/", "../../.." }), cwd));
+        try testResolvePosix(&[_][]const u8{ "a/b/c/", "../../.." }, cwd);
-        testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{"."}), cwd));
+        try testResolvePosix(&[_][]const u8{"."}, cwd);
     }
 }
 
@@ -683,66 +684,71 @@ test "resolveWindows" {
         return error.SkipZigTest;
     }
     if (builtin.os == .windows) {
-        const cwd = try process.getCwdAlloc(debug.global_allocator);
+        const cwd = try process.getCwdAlloc(testing.allocator);
+        defer testing.allocator.free(cwd);
         const parsed_cwd = windowsParsePath(cwd);
         {
-            const result = testResolveWindows(&[_][]const u8{ "/usr/local", "lib\\zig\\std\\array_list.zig" });
+            const expected = try join(testing.allocator, &[_][]const u8{
-            const expected = try join(debug.global_allocator, &[_][]const u8{
                 parsed_cwd.disk_designator,
                 "usr\\local\\lib\\zig\\std\\array_list.zig",
             });
+            defer testing.allocator.free(expected);
             if (parsed_cwd.kind == WindowsPath.Kind.Drive) {
                 expected[0] = asciiUpper(parsed_cwd.disk_designator[0]);
             }
-            testing.expect(mem.eql(u8, result, expected));
+            try testResolveWindows(&[_][]const u8{ "/usr/local", "lib\\zig\\std\\array_list.zig" }, expected);
         }
         {
-            const result = testResolveWindows(&[_][]const u8{ "usr/local", "lib\\zig" });
+            const expected = try join(testing.allocator, &[_][]const u8{
-            const expected = try join(debug.global_allocator, &[_][]const u8{
                 cwd,
                 "usr\\local\\lib\\zig",
             });
+            defer testing.allocator.free(expected);
             if (parsed_cwd.kind == WindowsPath.Kind.Drive) {
                 expected[0] = asciiUpper(parsed_cwd.disk_designator[0]);
             }
-            testing.expect(mem.eql(u8, result, expected));
+            try testResolveWindows(&[_][]const u8{ "usr/local", "lib\\zig" }, expected);
         }
     }
 
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:\\a\\b\\c", "/hi", "ok" }), "C:\\hi\\ok"));
+    try testResolveWindows(&[_][]const u8{ "c:\\a\\b\\c", "/hi", "ok" }, "C:\\hi\\ok");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/blah\\blah", "d:/games", "c:../a" }), "C:\\blah\\a"));
+    try testResolveWindows(&[_][]const u8{ "c:/blah\\blah", "d:/games", "c:../a" }, "C:\\blah\\a");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/blah\\blah", "d:/games", "C:../a" }), "C:\\blah\\a"));
+    try testResolveWindows(&[_][]const u8{ "c:/blah\\blah", "d:/games", "C:../a" }, "C:\\blah\\a");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/ignore", "d:\\a/b\\c/d", "\\e.exe" }), "D:\\e.exe"));
+    try testResolveWindows(&[_][]const u8{ "c:/ignore", "d:\\a/b\\c/d", "\\e.exe" }, "D:\\e.exe");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/ignore", "c:/some/file" }), "C:\\some\\file"));
+    try testResolveWindows(&[_][]const u8{ "c:/ignore", "c:/some/file" }, "C:\\some\\file");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "d:/ignore", "d:some/dir//" }), "D:\\ignore\\some\\dir"));
+    try testResolveWindows(&[_][]const u8{ "d:/ignore", "d:some/dir//" }, "D:\\ignore\\some\\dir");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "//server/share", "..", "relative\\" }), "\\\\server\\share\\relative"));
+    try testResolveWindows(&[_][]const u8{ "//server/share", "..", "relative\\" }, "\\\\server\\share\\relative");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/", "//" }), "C:\\"));
+    try testResolveWindows(&[_][]const u8{ "c:/", "//" }, "C:\\");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/", "//dir" }), "C:\\dir"));
+    try testResolveWindows(&[_][]const u8{ "c:/", "//dir" }, "C:\\dir");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/", "//server/share" }), "\\\\server\\share\\"));
+    try testResolveWindows(&[_][]const u8{ "c:/", "//server/share" }, "\\\\server\\share\\");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/", "//server//share" }), "\\\\server\\share\\"));
+    try testResolveWindows(&[_][]const u8{ "c:/", "//server//share" }, "\\\\server\\share\\");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "c:/", "///some//dir" }), "C:\\some\\dir"));
+    try testResolveWindows(&[_][]const u8{ "c:/", "///some//dir" }, "C:\\some\\dir");
-    testing.expect(mem.eql(u8, testResolveWindows(&[_][]const u8{ "C:\\foo\\tmp.3\\", "..\\tmp.3\\cycles\\root.js" }), "C:\\foo\\tmp.3\\cycles\\root.js"));
+    try testResolveWindows(&[_][]const u8{ "C:\\foo\\tmp.3\\", "..\\tmp.3\\cycles\\root.js" }, "C:\\foo\\tmp.3\\cycles\\root.js");
 }
 
 test "resolvePosix" {
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/a/b", "c" }), "/a/b/c"));
+    try testResolvePosix(&[_][]const u8{ "/a/b", "c" }, "/a/b/c");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/a/b", "c", "//d", "e///" }), "/d/e"));
+    try testResolvePosix(&[_][]const u8{ "/a/b", "c", "//d", "e///" }, "/d/e");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/a/b/c", "..", "../" }), "/a"));
+    try testResolvePosix(&[_][]const u8{ "/a/b/c", "..", "../" }, "/a");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/", "..", ".." }), "/"));
+    try testResolvePosix(&[_][]const u8{ "/", "..", ".." }, "/");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{"/a/b/c/"}), "/a/b/c"));
+    try testResolvePosix(&[_][]const u8{"/a/b/c/"}, "/a/b/c");
 
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/var/lib", "../", "file/" }), "/var/file"));
+    try testResolvePosix(&[_][]const u8{ "/var/lib", "../", "file/" }, "/var/file");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/var/lib", "/../", "file/" }), "/file"));
+    try testResolvePosix(&[_][]const u8{ "/var/lib", "/../", "file/" }, "/file");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/some/dir", ".", "/absolute/" }), "/absolute"));
+    try testResolvePosix(&[_][]const u8{ "/some/dir", ".", "/absolute/" }, "/absolute");
-    testing.expect(mem.eql(u8, testResolvePosix(&[_][]const u8{ "/foo/tmp.3/", "../tmp.3/cycles/root.js" }), "/foo/tmp.3/cycles/root.js"));
+    try testResolvePosix(&[_][]const u8{ "/foo/tmp.3/", "../tmp.3/cycles/root.js" }, "/foo/tmp.3/cycles/root.js");
 }
 
-fn testResolveWindows(paths: []const []const u8) []u8 {
+fn testResolveWindows(paths: []const []const u8, expected: []const u8) !void {
-    return resolveWindows(debug.global_allocator, paths) catch unreachable;
+    const actual = try resolveWindows(testing.allocator, paths);
+    defer testing.allocator.free(actual);
+    return testing.expect(mem.eql(u8, actual, expected));
 }
 
-fn testResolvePosix(paths: []const []const u8) []u8 {
+fn testResolvePosix(paths: []const []const u8, expected: []const u8) !void {
-    return resolvePosix(debug.global_allocator, paths) catch unreachable;
+    const actual = try resolvePosix(testing.allocator, paths);
+    defer testing.allocator.free(actual);
+    return testing.expect(mem.eql(u8, actual, expected));
 }
 
 /// If the path is a file in the current directory (no directory component)
@@ -1126,51 +1132,53 @@ test "relative" {
         // TODO https://github.com/ziglang/zig/issues/3288
         return error.SkipZigTest;
     }
-    testRelativeWindows("c:/blah\\blah", "d:/games", "D:\\games");
+    try testRelativeWindows("c:/blah\\blah", "d:/games", "D:\\games");
-    testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa", "..");
+    try testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa", "..");
-    testRelativeWindows("c:/aaaa/bbbb", "c:/cccc", "..\\..\\cccc");
+    try testRelativeWindows("c:/aaaa/bbbb", "c:/cccc", "..\\..\\cccc");
-    testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa/bbbb", "");
+    try testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa/bbbb", "");
-    testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa/cccc", "..\\cccc");
+    try testRelativeWindows("c:/aaaa/bbbb", "c:/aaaa/cccc", "..\\cccc");
-    testRelativeWindows("c:/aaaa/", "c:/aaaa/cccc", "cccc");
+    try testRelativeWindows("c:/aaaa/", "c:/aaaa/cccc", "cccc");
-    testRelativeWindows("c:/", "c:\\aaaa\\bbbb", "aaaa\\bbbb");
+    try testRelativeWindows("c:/", "c:\\aaaa\\bbbb", "aaaa\\bbbb");
-    testRelativeWindows("c:/aaaa/bbbb", "d:\\", "D:\\");
+    try testRelativeWindows("c:/aaaa/bbbb", "d:\\", "D:\\");
-    testRelativeWindows("c:/AaAa/bbbb", "c:/aaaa/bbbb", "");
+    try testRelativeWindows("c:/AaAa/bbbb", "c:/aaaa/bbbb", "");
-    testRelativeWindows("c:/aaaaa/", "c:/aaaa/cccc", "..\\aaaa\\cccc");
+    try testRelativeWindows("c:/aaaaa/", "c:/aaaa/cccc", "..\\aaaa\\cccc");
-    testRelativeWindows("C:\\foo\\bar\\baz\\quux", "C:\\", "..\\..\\..\\..");
+    try testRelativeWindows("C:\\foo\\bar\\baz\\quux", "C:\\", "..\\..\\..\\..");
-    testRelativeWindows("C:\\foo\\test", "C:\\foo\\test\\bar\\package.json", "bar\\package.json");
+    try testRelativeWindows("C:\\foo\\test", "C:\\foo\\test\\bar\\package.json", "bar\\package.json");
-    testRelativeWindows("C:\\foo\\bar\\baz-quux", "C:\\foo\\bar\\baz", "..\\baz");
+    try testRelativeWindows("C:\\foo\\bar\\baz-quux", "C:\\foo\\bar\\baz", "..\\baz");
-    testRelativeWindows("C:\\foo\\bar\\baz", "C:\\foo\\bar\\baz-quux", "..\\baz-quux");
+    try testRelativeWindows("C:\\foo\\bar\\baz", "C:\\foo\\bar\\baz-quux", "..\\baz-quux");
-    testRelativeWindows("\\\\foo\\bar", "\\\\foo\\bar\\baz", "baz");
+    try testRelativeWindows("\\\\foo\\bar", "\\\\foo\\bar\\baz", "baz");
-    testRelativeWindows("\\\\foo\\bar\\baz", "\\\\foo\\bar", "..");
+    try testRelativeWindows("\\\\foo\\bar\\baz", "\\\\foo\\bar", "..");
-    testRelativeWindows("\\\\foo\\bar\\baz-quux", "\\\\foo\\bar\\baz", "..\\baz");
+    try testRelativeWindows("\\\\foo\\bar\\baz-quux", "\\\\foo\\bar\\baz", "..\\baz");
-    testRelativeWindows("\\\\foo\\bar\\baz", "\\\\foo\\bar\\baz-quux", "..\\baz-quux");
+    try testRelativeWindows("\\\\foo\\bar\\baz", "\\\\foo\\bar\\baz-quux", "..\\baz-quux");
-    testRelativeWindows("C:\\baz-quux", "C:\\baz", "..\\baz");
+    try testRelativeWindows("C:\\baz-quux", "C:\\baz", "..\\baz");
-    testRelativeWindows("C:\\baz", "C:\\baz-quux", "..\\baz-quux");
+    try testRelativeWindows("C:\\baz", "C:\\baz-quux", "..\\baz-quux");
-    testRelativeWindows("\\\\foo\\baz-quux", "\\\\foo\\baz", "..\\baz");
+    try testRelativeWindows("\\\\foo\\baz-quux", "\\\\foo\\baz", "..\\baz");
-    testRelativeWindows("\\\\foo\\baz", "\\\\foo\\baz-quux", "..\\baz-quux");
+    try testRelativeWindows("\\\\foo\\baz", "\\\\foo\\baz-quux", "..\\baz-quux");
-    testRelativeWindows("C:\\baz", "\\\\foo\\bar\\baz", "\\\\foo\\bar\\baz");
+    try testRelativeWindows("C:\\baz", "\\\\foo\\bar\\baz", "\\\\foo\\bar\\baz");
-    testRelativeWindows("\\\\foo\\bar\\baz", "C:\\baz", "C:\\baz");
+    try testRelativeWindows("\\\\foo\\bar\\baz", "C:\\baz", "C:\\baz");
 
-    testRelativePosix("/var/lib", "/var", "..");
+    try testRelativePosix("/var/lib", "/var", "..");
-    testRelativePosix("/var/lib", "/bin", "../../bin");
+    try testRelativePosix("/var/lib", "/bin", "../../bin");
-    testRelativePosix("/var/lib", "/var/lib", "");
+    try testRelativePosix("/var/lib", "/var/lib", "");
-    testRelativePosix("/var/lib", "/var/apache", "../apache");
+    try testRelativePosix("/var/lib", "/var/apache", "../apache");
-    testRelativePosix("/var/", "/var/lib", "lib");
+    try testRelativePosix("/var/", "/var/lib", "lib");
-    testRelativePosix("/", "/var/lib", "var/lib");
+    try testRelativePosix("/", "/var/lib", "var/lib");
-    testRelativePosix("/foo/test", "/foo/test/bar/package.json", "bar/package.json");
+    try testRelativePosix("/foo/test", "/foo/test/bar/package.json", "bar/package.json");
-    testRelativePosix("/Users/a/web/b/test/mails", "/Users/a/web/b", "../..");
+    try testRelativePosix("/Users/a/web/b/test/mails", "/Users/a/web/b", "../..");
-    testRelativePosix("/foo/bar/baz-quux", "/foo/bar/baz", "../baz");
+    try testRelativePosix("/foo/bar/baz-quux", "/foo/bar/baz", "../baz");
-    testRelativePosix("/foo/bar/baz", "/foo/bar/baz-quux", "../baz-quux");
+    try testRelativePosix("/foo/bar/baz", "/foo/bar/baz-quux", "../baz-quux");
-    testRelativePosix("/baz-quux", "/baz", "../baz");
+    try testRelativePosix("/baz-quux", "/baz", "../baz");
-    testRelativePosix("/baz", "/baz-quux", "../baz-quux");
+    try testRelativePosix("/baz", "/baz-quux", "../baz-quux");
 }
 
-fn testRelativePosix(from: []const u8, to: []const u8, expected_output: []const u8) void {
+fn testRelativePosix(from: []const u8, to: []const u8, expected_output: []const u8) !void {
-    const result = relativePosix(debug.global_allocator, from, to) catch unreachable;
+    const result = try relativePosix(testing.allocator, from, to);
+    defer testing.allocator.free(result);
     testing.expectEqualSlices(u8, expected_output, result);
 }
 
-fn testRelativeWindows(from: []const u8, to: []const u8, expected_output: []const u8) void {
+fn testRelativeWindows(from: []const u8, to: []const u8, expected_output: []const u8) !void {
-    const result = relativeWindows(debug.global_allocator, from, to) catch unreachable;
+    const result = try relativeWindows(testing.allocator, from, to);
+    defer testing.allocator.free(result);
     testing.expectEqualSlices(u8, expected_output, result);
 }

lib/std/hash/auto_hash.zig

@@ -234,8 +234,8 @@ test "hash pointer" {
 test "hash slice shallow" {
     // Allocate one array dynamically so that we're assured it is not merged
     // with the other by the optimization passes.
-    const array1 = try std.heap.page_allocator.create([6]u32);
+    const array1 = try std.testing.allocator.create([6]u32);
-    defer std.heap.page_allocator.destroy(array1);
+    defer std.testing.allocator.destroy(array1);
     array1.* = [_]u32{ 1, 2, 3, 4, 5, 6 };
     const array2 = [_]u32{ 1, 2, 3, 4, 5, 6 };
     const a = array1[0..];
@@ -250,8 +250,8 @@ test "hash slice shallow" {
 test "hash slice deep" {
     // Allocate one array dynamically so that we're assured it is not merged
     // with the other by the optimization passes.
-    const array1 = try std.heap.page_allocator.create([6]u32);
+    const array1 = try std.testing.allocator.create([6]u32);
-    defer std.heap.page_allocator.destroy(array1);
+    defer std.testing.allocator.destroy(array1);
     array1.* = [_]u32{ 1, 2, 3, 4, 5, 6 };
     const array2 = [_]u32{ 1, 2, 3, 4, 5, 6 };
     const a = array1[0..];
@@ -278,7 +278,7 @@ test "hash struct deep" {
         }
     };
 
-    const allocator = std.heap.page_allocator;
+    const allocator = std.testing.allocator;
     const foo = try Foo.init(allocator, 123, 1.0, true);
     const bar = try Foo.init(allocator, 123, 1.0, true);
     const baz = try Foo.init(allocator, 123, 1.0, false);

lib/std/hash_map.zig

@@ -419,7 +419,7 @@ pub fn HashMap(comptime K: type, comptime V: type, comptime hash: fn (key: K) u3
 }
 
 test "basic hash map usage" {
-    var map = AutoHashMap(i32, i32).init(std.heap.page_allocator);
+    var map = AutoHashMap(i32, i32).init(std.testing.allocator);
     defer map.deinit();
 
     testing.expect((try map.put(1, 11)) == null);
@@ -463,7 +463,7 @@ test "basic hash map usage" {
 }
 
 test "iterator hash map" {
-    var reset_map = AutoHashMap(i32, i32).init(std.heap.page_allocator);
+    var reset_map = AutoHashMap(i32, i32).init(std.testing.allocator);
     defer reset_map.deinit();
 
     try reset_map.putNoClobber(1, 11);
@@ -509,7 +509,7 @@ test "iterator hash map" {
 }
 
 test "ensure capacity" {
-    var map = AutoHashMap(i32, i32).init(std.heap.page_allocator);
+    var map = AutoHashMap(i32, i32).init(std.testing.allocator);
     defer map.deinit();
 
     try map.ensureCapacity(20);

lib/std/heap.zig

@@ -711,6 +711,10 @@ pub const ThreadSafeFixedBufferAllocator = blk: {
             fn shrink(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
                 return old_mem[0..new_size];
             }
+
+            pub fn reset(self: *ThreadSafeFixedBufferAllocator) void {
+                self.end_index = 0;
+            }
         };
     }
 };

lib/std/heap/logging_allocator.zig

@@ -57,7 +57,7 @@ test "LoggingAllocator" {
     var slice_stream = std.io.SliceOutStream.init(buf[0..]);
     const stream = &slice_stream.stream;
 
-    const allocator = &LoggingAllocator.init(std.heap.page_allocator, @ptrCast(*AnyErrorOutStream, stream)).allocator;
+    const allocator = &LoggingAllocator.init(std.testing.allocator, @ptrCast(*AnyErrorOutStream, stream)).allocator;
 
     const ptr = try allocator.alloc(u8, 10);
     allocator.free(ptr);

lib/std/io.zig

@@ -891,7 +891,7 @@ pub fn readLineSlice(slice: []u8) ![]u8 {
 pub fn readLineSliceFrom(stream: var, slice: []u8) ![]u8 {
     // We cannot use Buffer.fromOwnedSlice, as it wants to append a null byte
     // after taking ownership, which would always require an allocation.
-    var buf = std.Buffer{ .list = std.ArrayList(u8).fromOwnedSlice(debug.failing_allocator, slice) };
+    var buf = std.Buffer{ .list = std.ArrayList(u8).fromOwnedSlice(testing.failing_allocator, slice) };
     try buf.resize(0);
     return try readLineFrom(stream, &buf);
 }

lib/std/linked_list.zig

@@ -143,7 +143,7 @@ pub fn SinglyLinkedList(comptime T: type) type {
 }
 
 test "basic SinglyLinkedList test" {
-    const allocator = debug.global_allocator;
+    const allocator = testing.allocator;
     var list = SinglyLinkedList(u32).init();
 
     var one = try list.createNode(1, allocator);
@@ -404,7 +404,7 @@ pub fn TailQueue(comptime T: type) type {
 }
 
 test "basic TailQueue test" {
-    const allocator = debug.global_allocator;
+    const allocator = testing.allocator;
     var list = TailQueue(u32).init();
 
     var one = try list.createNode(1, allocator);
@@ -456,7 +456,7 @@ test "basic TailQueue test" {
 }
 
 test "TailQueue concatenation" {
-    const allocator = debug.global_allocator;
+    const allocator = testing.allocator;
     var list1 = TailQueue(u32).init();
     var list2 = TailQueue(u32).init();
 

lib/std/mutex.zig

@@ -306,12 +306,6 @@ const TestContext = struct {
 };
 
 test "std.Mutex" {
-    var plenty_of_memory = try std.heap.page_allocator.alloc(u8, 300 * 1024);
-    defer std.heap.page_allocator.free(plenty_of_memory);
-
-    var fixed_buffer_allocator = std.heap.ThreadSafeFixedBufferAllocator.init(plenty_of_memory);
-    var a = &fixed_buffer_allocator.allocator;
-
     var mutex = Mutex.init();
     defer mutex.deinit();
 

lib/std/os/test.zig

@@ -9,7 +9,7 @@ const elf = std.elf;
 const File = std.fs.File;
 const Thread = std.Thread;
 
-const a = std.debug.global_allocator;
+const a = std.testing.allocator;
 
 const builtin = @import("builtin");
 const AtomicRmwOp = builtin.AtomicRmwOp;
@@ -235,8 +235,8 @@ test "pipe" {
 }
 
 test "argsAlloc" {
-    var args = try std.process.argsAlloc(std.heap.page_allocator);
+    var args = try std.process.argsAlloc(std.testing.allocator);
-    std.process.argsFree(std.heap.page_allocator, args);
+    std.process.argsFree(std.testing.allocator, args);
 }
 
 test "memfd_create" {

lib/std/packed_int_array.zig

@@ -604,7 +604,7 @@ test "PackedIntArray at end of available memory" {
         p: PackedArray,
     };
 
-    const allocator = std.heap.page_allocator;
+    const allocator = std.testing.allocator;
 
     var pad = try allocator.create(Padded);
     defer allocator.destroy(pad);
@@ -618,7 +618,7 @@ test "PackedIntSlice at end of available memory" {
     }
     const PackedSlice = PackedIntSlice(u11);
 
-    const allocator = std.heap.page_allocator;
+    const allocator = std.testing.allocator;
 
     var page = try allocator.alloc(u8, std.mem.page_size);
     defer allocator.free(page);

lib/std/priority_queue.zig

@@ -1,10 +1,10 @@
 const std = @import("std.zig");
 const Allocator = std.mem.Allocator;
-const debug = std.debug;
+const assert = std.debug.assert;
-const assert = debug.assert;
+const testing = std.testing;
-const expect = std.testing.expect;
+const expect = testing.expect;
-const expectEqual = std.testing.expectEqual;
+const expectEqual = testing.expectEqual;
-const expectError = std.testing.expectError;
+const expectError = testing.expectError;
 
 /// Priority queue for storing generic data. Initialize with `init`.
 pub fn PriorityQueue(comptime T: type) type {
@@ -239,7 +239,7 @@ fn greaterThan(a: u32, b: u32) bool {
 const PQ = PriorityQueue(u32);
 
 test "std.PriorityQueue: add and remove min heap" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     try queue.add(54);
@@ -257,7 +257,7 @@ test "std.PriorityQueue: add and remove min heap" {
 }
 
 test "std.PriorityQueue: add and remove same min heap" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     try queue.add(1);
@@ -275,14 +275,14 @@ test "std.PriorityQueue: add and remove same min heap" {
 }
 
 test "std.PriorityQueue: removeOrNull on empty" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     expect(queue.removeOrNull() == null);
 }
 
 test "std.PriorityQueue: edge case 3 elements" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     try queue.add(9);
@@ -294,7 +294,7 @@ test "std.PriorityQueue: edge case 3 elements" {
 }
 
 test "std.PriorityQueue: peek" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     expect(queue.peek() == null);
@@ -306,7 +306,7 @@ test "std.PriorityQueue: peek" {
 }
 
 test "std.PriorityQueue: sift up with odd indices" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
     const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
     for (items) |e| {
@@ -320,7 +320,7 @@ test "std.PriorityQueue: sift up with odd indices" {
 }
 
 test "std.PriorityQueue: addSlice" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
     const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
     try queue.addSlice(items[0..]);
@@ -333,8 +333,8 @@ test "std.PriorityQueue: addSlice" {
 
 test "std.PriorityQueue: fromOwnedSlice" {
     const items = [_]u32{ 15, 7, 21, 14, 13, 22, 12, 6, 7, 25, 5, 24, 11, 16, 15, 24, 2, 1 };
-    const heap_items = try std.mem.dupe(debug.global_allocator, u32, items[0..]);
+    const heap_items = try std.mem.dupe(testing.allocator, u32, items[0..]);
-    var queue = PQ.fromOwnedSlice(debug.global_allocator, lessThan, heap_items[0..]);
+    var queue = PQ.fromOwnedSlice(testing.allocator, lessThan, heap_items[0..]);
     defer queue.deinit();
 
     const sorted_items = [_]u32{ 1, 2, 5, 6, 7, 7, 11, 12, 13, 14, 15, 15, 16, 21, 22, 24, 24, 25 };
@@ -344,7 +344,7 @@ test "std.PriorityQueue: fromOwnedSlice" {
 }
 
 test "std.PriorityQueue: add and remove max heap" {
-    var queue = PQ.init(debug.global_allocator, greaterThan);
+    var queue = PQ.init(testing.allocator, greaterThan);
     defer queue.deinit();
 
     try queue.add(54);
@@ -362,7 +362,7 @@ test "std.PriorityQueue: add and remove max heap" {
 }
 
 test "std.PriorityQueue: add and remove same max heap" {
-    var queue = PQ.init(debug.global_allocator, greaterThan);
+    var queue = PQ.init(testing.allocator, greaterThan);
     defer queue.deinit();
 
     try queue.add(1);
@@ -380,8 +380,8 @@ test "std.PriorityQueue: add and remove same max heap" {
 }
 
 test "std.PriorityQueue: iterator" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
-    var map = std.AutoHashMap(u32, void).init(debug.global_allocator);
+    var map = std.AutoHashMap(u32, void).init(testing.allocator);
     defer {
         queue.deinit();
         map.deinit();
@@ -402,7 +402,7 @@ test "std.PriorityQueue: iterator" {
 }
 
 test "std.PriorityQueue: remove at index" {
-    var queue = PQ.init(debug.global_allocator, lessThan);
+    var queue = PQ.init(testing.allocator, lessThan);
     defer queue.deinit();
 
     try queue.add(3);

lib/std/process.zig

@@ -79,7 +79,7 @@ pub fn getEnvMap(allocator: *Allocator) !BufMap {
         // https://github.com/WebAssembly/WASI/issues/27
         var environ = try allocator.alloc(?[*:0]u8, environ_count + 1);
         defer allocator.free(environ);
-        var environ_buf = try std.heap.page_allocator.alloc(u8, environ_buf_size);
+        var environ_buf = try allocator.alloc(u8, environ_buf_size);
         defer allocator.free(environ_buf);
 
         const environ_get_ret = os.wasi.environ_get(environ.ptr, environ_buf.ptr);
@@ -114,7 +114,7 @@ pub fn getEnvMap(allocator: *Allocator) !BufMap {
 }
 
 test "os.getEnvMap" {
-    var env = try getEnvMap(std.debug.global_allocator);
+    var env = try getEnvMap(std.testing.allocator);
     defer env.deinit();
 }
 
@@ -165,7 +165,7 @@ pub fn getEnvVarOwned(allocator: *mem.Allocator, key: []const u8) GetEnvVarOwned
 }
 
 test "os.getEnvVarOwned" {
-    var ga = std.debug.global_allocator;
+    var ga = std.testing.allocator;
     testing.expectError(error.EnvironmentVariableNotFound, getEnvVarOwned(ga, "BADENV"));
 }
 
@@ -492,10 +492,11 @@ test "windows arg parsing" {
 fn testWindowsCmdLine(input_cmd_line: [*]const u8, expected_args: []const []const u8) void {
     var it = ArgIteratorWindows.initWithCmdLine(input_cmd_line);
     for (expected_args) |expected_arg| {
-        const arg = it.next(std.debug.global_allocator).? catch unreachable;
+        const arg = it.next(std.testing.allocator).? catch unreachable;
+        defer std.testing.allocator.free(arg);
         testing.expectEqualSlices(u8, expected_arg, arg);
     }
-    testing.expect(it.next(std.debug.global_allocator) == null);
+    testing.expect(it.next(std.testing.allocator) == null);
 }
 
 pub const UserInfo = struct {

lib/std/segmented_list.zig

@@ -339,7 +339,7 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
 }
 
 test "std.SegmentedList" {
-    var a = std.heap.page_allocator;
+    var a = std.testing.allocator;
 
     try testSegmentedList(0, a);
     try testSegmentedList(1, a);

lib/std/special/test_runner.zig

@@ -13,6 +13,8 @@ pub fn main() anyerror!void {
     };
 
     for (test_fn_list) |test_fn, i| {
+        std.testing.base_allocator_instance.reset();
+
         var test_node = root_node.start(test_fn.name, null);
         test_node.activate();
         progress.refresh();
@@ -22,6 +24,10 @@ pub fn main() anyerror!void {
         if (test_fn.func()) |_| {
             ok_count += 1;
             test_node.end();
+            std.testing.allocator_instance.validate() catch |err| switch (err) {
+                error.Leak => std.debug.panic("", .{}),
+                else => std.debug.panic("error.{}", .{@errorName(err)}),
+            };
             if (progress.terminal == null) std.debug.warn("OK\n", .{});
         } else |err| switch (err) {
             error.SkipZigTest => {

lib/std/testing.zig

@@ -2,6 +2,18 @@ const builtin = @import("builtin");
 const TypeId = builtin.TypeId;
 const std = @import("std.zig");
 
+pub const LeakCountAllocator = @import("testing/leak_count_allocator.zig").LeakCountAllocator;
+pub const FailingAllocator = @import("testing/failing_allocator.zig").FailingAllocator;
+
+/// This should only be used in temporary test programs.
+pub const allocator = &allocator_instance.allocator;
+pub var allocator_instance = LeakCountAllocator.init(&base_allocator_instance.allocator);
+
+pub const failing_allocator = &FailingAllocator.init(&base_allocator_instance.allocator, 0).allocator;
+
+pub var base_allocator_instance = std.heap.ThreadSafeFixedBufferAllocator.init(allocator_mem[0..]);
+var allocator_mem: [512 * 1024]u8 = undefined;
+
 /// This function is intended to be used only in tests. It prints diagnostics to stderr
 /// and then aborts when actual_error_union is not expected_error.
 pub fn expectError(expected_error: anyerror, actual_error_union: var) void {

lib/std/testing/leak_count_allocator.zig

@@ -0,0 +1,50 @@
+const std = @import("../std.zig");
+
+/// This allocator is used in front of another allocator and counts the numbers of allocs and frees.
+/// The test runner asserts every alloc has a corresponding free at the end of each test.
+///
+/// The detection algorithm is incredibly primitive and only accounts for number of calls.
+/// This should be replaced by the general purpose debug allocator.
+pub const LeakCountAllocator = struct {
+    count: usize,
+    allocator: std.mem.Allocator,
+    internal_allocator: *std.mem.Allocator,
+
+    pub fn init(allocator: *std.mem.Allocator) LeakCountAllocator {
+        return .{
+            .count = 0,
+            .allocator = .{
+                .reallocFn = realloc,
+                .shrinkFn = shrink,
+            },
+            .internal_allocator = allocator,
+        };
+    }
+
+    fn realloc(allocator: *std.mem.Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) ![]u8 {
+        const self = @fieldParentPtr(LeakCountAllocator, "allocator", allocator);
+        var data = try self.internal_allocator.reallocFn(self.internal_allocator, old_mem, old_align, new_size, new_align);
+        if (old_mem.len == 0) {
+            self.count += 1;
+        }
+        return data;
+    }
+
+    fn shrink(allocator: *std.mem.Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
+        const self = @fieldParentPtr(LeakCountAllocator, "allocator", allocator);
+        if (new_size == 0) {
+            if (self.count == 0) {
+                std.debug.panic("error - too many calls to free, most likely double free", .{});
+            }
+            self.count -= 1;
+        }
+        return self.internal_allocator.shrinkFn(self.internal_allocator, old_mem, old_align, new_size, new_align);
+    }
+
+    pub fn validate(self: LeakCountAllocator) !void {
+        if (self.count > 0) {
+            std.debug.warn("error - detected leaked allocations without matching free: {}\n", .{self.count});
+            return error.Leak;
+        }
+    }
+};

lib/std/unicode.zig

@@ -501,14 +501,16 @@ test "utf16leToUtf8" {
     {
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 'A');
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 'a');
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "Aa"));
     }
 
     {
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 0x80);
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 0xffff);
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "\xc2\x80" ++ "\xef\xbf\xbf"));
     }
 
@@ -516,7 +518,8 @@ test "utf16leToUtf8" {
         // the values just outside the surrogate half range
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 0xd7ff);
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 0xe000);
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "\xed\x9f\xbf" ++ "\xee\x80\x80"));
     }
 
@@ -524,7 +527,8 @@ test "utf16leToUtf8" {
         // smallest surrogate pair
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 0xd800);
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 0xdc00);
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "\xf0\x90\x80\x80"));
     }
 
@@ -532,14 +536,16 @@ test "utf16leToUtf8" {
         // largest surrogate pair
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 0xdbff);
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 0xdfff);
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "\xf4\x8f\xbf\xbf"));
     }
 
     {
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[0..], 0xdbff);
         mem.writeIntSliceLittle(u16, utf16le_as_bytes[2..], 0xdc00);
-        const utf8 = try utf16leToUtf8Alloc(std.debug.global_allocator, &utf16le);
+        const utf8 = try utf16leToUtf8Alloc(std.testing.allocator, &utf16le);
+        defer std.testing.allocator.free(utf8);
         testing.expect(mem.eql(u8, utf8, "\xf4\x8f\xb0\x80"));
     }
 }

lib/std/zig/ast.zig

@@ -2287,7 +2287,7 @@ pub const Node = struct {
 test "iterate" {
     var root = Node.Root{
         .base = Node{ .id = Node.Id.Root },
-        .decls = Node.Root.DeclList.init(std.debug.global_allocator),
+        .decls = Node.Root.DeclList.init(std.testing.allocator),
         .eof_token = 0,
     };
     var base = &root.base;

lib/std/zig/parser_test.zig

@@ -2773,7 +2773,7 @@ fn testTransform(source: []const u8, expected_source: []const u8) !void {
     const needed_alloc_count = x: {
         // Try it once with unlimited memory, make sure it works
         var fixed_allocator = std.heap.FixedBufferAllocator.init(fixed_buffer_mem[0..]);
-        var failing_allocator = std.debug.FailingAllocator.init(&fixed_allocator.allocator, maxInt(usize));
+        var failing_allocator = std.testing.FailingAllocator.init(&fixed_allocator.allocator, maxInt(usize));
         var anything_changed: bool = undefined;
         const result_source = try testParse(source, &failing_allocator.allocator, &anything_changed);
         if (!mem.eql(u8, result_source, expected_source)) {
@@ -2797,7 +2797,7 @@ fn testTransform(source: []const u8, expected_source: []const u8) !void {
     var fail_index: usize = 0;
     while (fail_index < needed_alloc_count) : (fail_index += 1) {
         var fixed_allocator = std.heap.FixedBufferAllocator.init(fixed_buffer_mem[0..]);
-        var failing_allocator = std.debug.FailingAllocator.init(&fixed_allocator.allocator, fail_index);
+        var failing_allocator = std.testing.FailingAllocator.init(&fixed_allocator.allocator, fail_index);
         var anything_changed: bool = undefined;
         if (testParse(source, &failing_allocator.allocator, &anything_changed)) |_| {
             return error.NondeterministicMemoryUsage;

src-self-hosted/c_tokenizer.zig

@@ -866,7 +866,7 @@ fn expectTokens(tl: *TokenList, src: [*:0]const u8, expected: []CToken) void {
 }
 
 test "tokenize macro" {
-    var tl = TokenList.init(std.heap.page_allocator);
+    var tl = TokenList.init(std.testing.allocator);
     defer tl.deinit();
 
     expectTokens(&tl, "TEST(0\n", &[_]CToken{
@@ -904,7 +904,7 @@ test "tokenize macro" {
 }
 
 test "tokenize macro ops" {
-    var tl = TokenList.init(std.heap.page_allocator);
+    var tl = TokenList.init(std.testing.allocator);
     defer tl.deinit();
 
     expectTokens(&tl, "ADD A + B", &[_]CToken{

test/cli.zig

@@ -8,7 +8,7 @@ const ChildProcess = std.ChildProcess;
 var a: *std.mem.Allocator = undefined;
 
 pub fn main() !void {
-    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
     defer arena.deinit();
 
     var arg_it = process.args();

test/compare_output.zig

@@ -445,7 +445,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
             \\const std = @import("std");
             \\const io = std.io;
             \\const os = std.os;
-            \\const allocator = std.debug.global_allocator;
+            \\const allocator = std.testing.allocator;
             \\
             \\pub fn main() !void {
             \\    var args_it = std.process.args();
@@ -486,7 +486,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
             \\const std = @import("std");
             \\const io = std.io;
             \\const os = std.os;
-            \\const allocator = std.debug.global_allocator;
+            \\const allocator = std.testing.allocator;
             \\
             \\pub fn main() !void {
             \\    var args_it = std.process.args();

test/compile_errors.zig

@@ -5765,7 +5765,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         \\
         \\export fn entry() void {
         \\    const a = MdNode.Header {
-        \\        .text = MdText.init(&std.debug.global_allocator),
+        \\        .text = MdText.init(&std.testing.allocator),
         \\        .weight = HeaderWeight.H1,
         \\    };
         \\}

test/stage1/behavior/async_fn.zig

@@ -410,8 +410,8 @@ test "heap allocated async function frame" {
         var x: i32 = 42;
 
         fn doTheTest() !void {
-            const frame = try std.heap.page_allocator.create(@Frame(someFunc));
+            const frame = try std.testing.allocator.create(@Frame(someFunc));
-            defer std.heap.page_allocator.destroy(frame);
+            defer std.testing.allocator.destroy(frame);
 
             expect(x == 42);
             frame.* = async someFunc();
@@ -671,7 +671,7 @@ fn testAsyncAwaitTypicalUsage(
         }
 
         fn amain() !void {
-            const allocator = std.heap.page_allocator; // TODO once we have the debug allocator, use that, so that this can detect leaks
+            const allocator = std.testing.allocator;
             var download_frame = async fetchUrl(allocator, "https://example.com/");
             var download_awaited = false;
             errdefer if (!download_awaited) {
@@ -935,12 +935,12 @@ fn recursiveAsyncFunctionTest(comptime suspending_implementation: bool) type {
                 _ = async amain(&result);
                 return result;
             } else {
-                return fib(std.heap.page_allocator, 10) catch unreachable;
+                return fib(std.testing.allocator, 10) catch unreachable;
             }
         }
 
         fn amain(result: *u32) void {
-            var x = async fib(std.heap.page_allocator, 10);
+            var x = async fib(std.testing.allocator, 10);
             result.* = (await x) catch unreachable;
         }
     };

test/stage1/behavior/const_slice_child.zig

@@ -1,6 +1,7 @@
 const std = @import("std");
 const debug = std.debug;
-const expect = std.testing.expect;
+const testing = std.testing;
+const expect = testing.expect;
 
 var argv: [*]const [*]const u8 = undefined;
 
@@ -22,7 +23,8 @@ fn foo(args: [][]const u8) void {
 }
 
 fn bar(argc: usize) void {
-    const args = debug.global_allocator.alloc([]const u8, argc) catch unreachable;
+    const args = testing.allocator.alloc([]const u8, argc) catch unreachable;
+    defer testing.allocator.free(args);
     for (args) |_, i| {
         const ptr = argv[i];
         args[i] = ptr[0..strlen(ptr)];

test/standalone/brace_expansion/main.zig

@@ -201,7 +201,10 @@ pub fn main() !void {
 }
 
 test "invalid inputs" {
-    global_allocator = std.debug.global_allocator;
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+
+    global_allocator = &arena.allocator;
 
     expectError("}ABC", error.InvalidInput);
     expectError("{ABC", error.InvalidInput);
@@ -222,7 +225,10 @@ fn expectError(test_input: []const u8, expected_err: anyerror) void {
 }
 
 test "valid inputs" {
-    global_allocator = std.debug.global_allocator;
+    var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
+    defer arena.deinit();
+
+    global_allocator = &arena.allocator;
 
     expectExpansion("{x,y,z}", "x y z");
     expectExpansion("{A,B}{x,y}", "Ax Ay Bx By");

test/standalone/cat/main.zig

@@ -4,7 +4,7 @@ const process = std.process;
 const fs = std.fs;
 const mem = std.mem;
 const warn = std.debug.warn;
-const allocator = std.debug.global_allocator;
+const allocator = std.testing.allocator;
 
 pub fn main() !void {
     var args_it = process.args();

test/standalone/empty_env/main.zig

@@ -1,6 +1,6 @@
 const std = @import("std");
 
 pub fn main() void {
-    const env_map = std.process.getEnvMap(std.debug.global_allocator) catch @panic("unable to get env map");
+    const env_map = std.process.getEnvMap(std.testing.allocator) catch @panic("unable to get env map");
     std.testing.expect(env_map.count() == 0);
 }

test/standalone/load_dynamic_library/main.zig

@@ -1,8 +1,8 @@
 const std = @import("std");
 
 pub fn main() !void {
-    const args = try std.process.argsAlloc(std.debug.global_allocator);
+    const args = try std.process.argsAlloc(std.testing.allocator);
-    defer std.process.argsFree(std.debug.global_allocator, args);
+    defer std.process.argsFree(std.testing.allocator, args);
 
     const dynlib_name = args[1];