zig

commit 314ce5465dfdc9f4d1e2d178704b47666d541fc4 (tree)
parent 5735ce39ae5a9fb2bc2ac9f5a722276c291b28bc
Author: Andrew Kelley <andrew@ziglang.org>
Date:   Sun,  3 Jul 2022 22:18:05 -0700

std: better definition for std.os.linux.epoll_event

The previous definition depends on a non-lang-spec-compliant memory
layout for packed structs, which happens to trigger #11989 in stage2.

This commit changes the struct to be an extern struct with an
align(4) field. However, stage1 cannot handle this, so conditional
compilation logic is used to select different struct definitions
depending on stage1 vs stage2.

This works around #11989 but does not solve the underlying problem -
putting an extern union inside a packed struct will still trigger the
assert.

After this, both stage1 and stage2 std lib tests run assertion-clean
with a debug LLVM 13.

Diffstat:
M
lib/std/os/linux.zig
 | 
19
++++++++++++-------

1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
@@ -3222,16 +3222,21 @@ pub const epoll_data = extern union {
     @"u64": u64,
 };
 
-// On x86_64 the structure is packed so that it matches the definition of its
-// 32bit counterpart
-pub const epoll_event = switch (native_arch) {
-    .x86_64 => packed struct {
-        events: u32,
-        data: epoll_data,
+pub const epoll_event = switch (builtin.zig_backend) {
+    // stage1 crashes with the align(4) field so we have this workaround
+    .stage1 => switch (native_arch) {
+        .x86_64 => packed struct {
+            events: u32,
+            data: epoll_data,
+        },
+        else => extern struct {
+            events: u32,
+            data: epoll_data,
+        },
     },
     else => extern struct {
         events: u32,
-        data: epoll_data,
+        data: epoll_data align(4),
     },
 };