From ae15022406e5d59787195130cfd5261c6336f41c Mon Sep 17 00:00:00 2001
From: LemonBoy <thatlemon@gmail.com>
Date: Sun, 25 Apr 2021 16:50:41 +0200
Subject: [PATCH] translate-c: Fix casting of function pointers

The @ptrCast(X, @alignCast(@alignOf(T), Y)) pattern is only correct if T
is not a function type or a pointer, in that case the @alignOf refers to
the pointer itself and not to the pointee type.
---
 src/translate_c.zig     |  2 +-
 src/translate_c/ast.zig | 12 +++++++++++-
 test/translate_c.zig    | 18 +++++++++---------
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/src/translate_c.zig b/src/translate_c.zig
index 60b3961e6e..0a722ab3b4 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -3539,7 +3539,7 @@ fn transCPtrCast(
             expr
         else blk: {
             const child_type_node = try transQualType(c, scope, child_type, loc);
-            const alignof = try Tag.alignof.create(c.arena, child_type_node);
+            const alignof = try Tag.std_meta_alignment.create(c.arena, child_type_node);
             const align_cast = try Tag.align_cast.create(c.arena, .{ .lhs = alignof, .rhs = expr });
             break :blk align_cast;
         };
diff --git a/src/translate_c/ast.zig b/src/translate_c/ast.zig
index 61d28bb22d..2e75bf1182 100644
--- a/src/translate_c/ast.zig
+++ b/src/translate_c/ast.zig
@@ -120,8 +120,11 @@ pub const Node = extern union {
         std_math_Log2Int,
         /// @intCast(lhs, rhs)
         int_cast,
-        /// @rem(lhs, rhs)
+        /// @import("std").meta.promoteIntLiteral(value, type, radix)
         std_meta_promoteIntLiteral,
+        /// @import("std").meta.alignment(value)
+        std_meta_alignment,
+        /// @rem(lhs, rhs)
         rem,
         /// @divTrunc(lhs, rhs)
         div_trunc,
@@ -260,6 +263,7 @@ pub const Node = extern union {
                 .switch_else,
                 .block_single,
                 .std_meta_sizeof,
+                .std_meta_alignment,
                 .bool_to_int,
                 .sizeof,
                 .alignof,
@@ -876,6 +880,11 @@ fn renderNode(c: *Context, node: Node) Allocator.Error!NodeIndex {
             const import_node = try renderStdImport(c, "meta", "promoteIntLiteral");
             return renderCall(c, import_node, &.{ payload.type, payload.value, payload.radix });
         },
+        .std_meta_alignment => {
+            const payload = node.castTag(.std_meta_alignment).?.data;
+            const import_node = try renderStdImport(c, "meta", "alignment");
+            return renderCall(c, import_node, &.{payload});
+        },
         .std_meta_sizeof => {
             const payload = node.castTag(.std_meta_sizeof).?.data;
             const import_node = try renderStdImport(c, "meta", "sizeof");
@@ -2144,6 +2153,7 @@ fn renderNodeGrouped(c: *Context, node: Node) !NodeIndex {
         .typeof,
         .typeinfo,
         .std_meta_sizeof,
+        .std_meta_alignment,
         .std_meta_cast,
         .std_meta_promoteIntLiteral,
         .std_meta_vector,
diff --git a/test/translate_c.zig b/test/translate_c.zig
index 846eec0d62..4021210b29 100644
--- a/test/translate_c.zig
+++ b/test/translate_c.zig
@@ -1363,7 +1363,7 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
     , &[_][]const u8{
         \\pub export fn ptrcast() [*c]f32 {
         \\    var a: [*c]c_int = undefined;
-        \\    return @ptrCast([*c]f32, @alignCast(@alignOf(f32), a));
+        \\    return @ptrCast([*c]f32, @alignCast(@import("std").meta.alignment(f32), a));
         \\}
     });
 
@@ -1387,16 +1387,16 @@ pub fn addCases(cases: *tests.TranslateCContext) void {
         \\pub export fn test_ptr_cast() void {
         \\    var p: ?*c_void = undefined;
         \\    {
-        \\        var to_char: [*c]u8 = @ptrCast([*c]u8, @alignCast(@alignOf(u8), p));
-        \\        var to_short: [*c]c_short = @ptrCast([*c]c_short, @alignCast(@alignOf(c_short), p));
-        \\        var to_int: [*c]c_int = @ptrCast([*c]c_int, @alignCast(@alignOf(c_int), p));
-        \\        var to_longlong: [*c]c_longlong = @ptrCast([*c]c_longlong, @alignCast(@alignOf(c_longlong), p));
+        \\        var to_char: [*c]u8 = @ptrCast([*c]u8, @alignCast(@import("std").meta.alignment(u8), p));
+        \\        var to_short: [*c]c_short = @ptrCast([*c]c_short, @alignCast(@import("std").meta.alignment(c_short), p));
+        \\        var to_int: [*c]c_int = @ptrCast([*c]c_int, @alignCast(@import("std").meta.alignment(c_int), p));
+        \\        var to_longlong: [*c]c_longlong = @ptrCast([*c]c_longlong, @alignCast(@import("std").meta.alignment(c_longlong), p));
         \\    }
         \\    {
-        \\        var to_char: [*c]u8 = @ptrCast([*c]u8, @alignCast(@alignOf(u8), p));
-        \\        var to_short: [*c]c_short = @ptrCast([*c]c_short, @alignCast(@alignOf(c_short), p));
-        \\        var to_int: [*c]c_int = @ptrCast([*c]c_int, @alignCast(@alignOf(c_int), p));
-        \\        var to_longlong: [*c]c_longlong = @ptrCast([*c]c_longlong, @alignCast(@alignOf(c_longlong), p));
+        \\        var to_char: [*c]u8 = @ptrCast([*c]u8, @alignCast(@import("std").meta.alignment(u8), p));
+        \\        var to_short: [*c]c_short = @ptrCast([*c]c_short, @alignCast(@import("std").meta.alignment(c_short), p));
+        \\        var to_int: [*c]c_int = @ptrCast([*c]c_int, @alignCast(@import("std").meta.alignment(c_int), p));
+        \\        var to_longlong: [*c]c_longlong = @ptrCast([*c]c_longlong, @alignCast(@import("std").meta.alignment(c_longlong), p));
         \\    }
         \\}
     });