i686-pc-windows-gnu broken on CI

[gnzlbg]

The i686-pc-windows-gnu target has been disabled on CI because it fails with the following segmentation fault:

error: test failed, to rerun pass '--test main'

Caused by:
  process didn't exit successfully: `D:\a\1\s\target\i686-pc-windows-gnu\debug\deps\main-65866843958a68e7.exe` (exit code: 0xc0000005, STATUS_ACCESS_VIOLATION)
./ci/run.sh: line 93:  1846 Segmentation fault      cargo test -vv $opt --no-default-features --manifest-path libc-test/Cargo.toml --target "${TARGET}"

For example, see: https://dev.azure.com/rust-lang2/libc/_build/results?buildId=608

This issue tracks re-enabling CI for this target. Even though this is a tier-1 target, it has been broken for a sufficiently long time that new releases of libc won't be tested against it, and probably rust-lang/rust libc version will be updated to one of those sooner or later. Without a debugger, there is not much I can do here.

cc @mati865 @retep998 (feel free to ping windows users that might be able to investigate)

[mati865]

Latest nightly has fix for i686 miscompilation: rust-lang/rust#66318
Can you retry the build?
It doesn't help.

[mati865]

Hopefully useful:

(lldb) r
Process 11012 launched: 'D:\msys64\tmp\libc\target\i686-pc-windows-gnu\debug\deps\main-fc7d8e49f1073eac.exe' (i686)
RUNNING ALL TESTS
Process 11012 stopped
* thread #1, stop reason = Exception 0xc0000005 encountered at address 0x4adab0: Access violation writing location 0x2ef71bd1
    frame #0: 0x004adab0 main-fc7d8e49f1073eac.exe`__test_roundtrip_max_align_t(value=max_align_t @ 0x009bfa90, rust_size=1996201872, error=0x2ef71bd1, pad="") at main.c:4583:28
   4580                         "size of max_align_t is %d in C and %d in Rust\n",
   4581                         (int)size, (int)rust_size
   4582                     );
-> 4583                     *error = 1;
                                   ^
   4584                     return value;
   4585                 }
   4586                 int i = 0;
(lldb) bt
(lldb) bt
* thread #1, stop reason = Exception 0xc0000005 encountered at address 0x4adab0: Access violation writing location 0x2ef71bd1
  * frame #0: 0x004adab0 main-fc7d8e49f1073eac.exe`__test_roundtrip_max_align_t

(value=max_align_t @ 0x009bfa90, rust_size=1996201872, error=0x2ef71bd1, pad="") at main.c:4583:28
    frame #1: 0x00437768 main-fc7d8e49f1073eac.exe`main::roundtrip_max_align_t::h65d307f4f71a6fd7 at main.rs:10705:30
    frame #2: 0x00438309 main-fc7d8e49f1073eac.exe`main::run_all::h3dd94fce5ecf1967 at main.rs:11128:1
    frame #3: 0x0040726b main-fc7d8e49f1073eac.exe`main::main::hdad19dffed1e8e93 at main.rs:10:17
    frame #4: 0x00401709 main-fc7d8e49f1073eac.exe`std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::h88bbd130d597fbb4 at rt.rs:67:34
    frame #5: 0x0045bb17 main-fc7d8e49f1073eac.exe`std::sys_common::backtrace::__rust_begin_short_backtrace::ha765656654808a54 [inlined] std::rt::lang_start_internal::_$u7b$$u7b$closure$u7d$$u7d$::_$u7b$$u7b$closure$u7d$$u7d$::h1cb0c3cf3d0f3b7b at rt.rs:52:73
    frame #6: 0x0045bb13 main-fc7d8e49f1073eac.exe`std::sys_common::backtrace::__rust_begin_short_backtrace::ha765656654808a54 at backtrace.rs:130
    frame #7: 0x0045f459 main-fc7d8e49f1073eac.exe`std::rt::lang_start_internal::h848f63bc4d320e91 [inlined] std::rt::lang_start_internal::_$u7b$$u7b$closure$u7d$$u7d$::h99b24a7dbe4a88ad at rt.rs:52:13
    frame #8: 0x0045f450 main-fc7d8e49f1073eac.exe`std::rt::lang_start_internal::h848f63bc4d320e91 [inlined] std::panicking::try::do_call::hf91bc4678426bdd4 at panicking.rs:331
    frame #9: 0x0045f450 main-fc7d8e49f1073eac.exe`std::rt::lang_start_internal::h848f63bc4d320e91 [inlined] std::panicking::try::hee89baf923f68bc0 at panicking.rs:274
    frame #10: 0x0045f450 main-fc7d8e49f1073eac.exe`std::rt::lang_start_internal::h848f63bc4d320e91 [inlined] std::panic::catch_unwind::h64b2c4628ae51fc5 at panic.rs:394
    frame #11: 0x0045f450 main-fc7d8e49f1073eac.exe`std::rt::lang_start_internal::h848f63bc4d320e91 at rt.rs:51
    frame #12: 0x004016f0 main-fc7d8e49f1073eac.exe`std::rt::lang_start::h1dda6c3e8dc7faa1(main=(main-fc7d8e49f1073eac.exe`main::main::hdad19dffed1e8e93 at main.rs:8), argc=1, argv=0x01412d08) at rt.rs:67:5
    frame #13: 0x00438643 main-fc7d8e49f1073eac.exe`_main + 51
    frame #14: 0x00401386 main-fc7d8e49f1073eac.exe`__tmainCRTStartup at crtexe.c:339:15
    frame #15: 0x74926359 kernel32.dll`BaseThreadInitThunk + 25
    frame #16: 0x76fa7b74 ntdll.dll`RtlGetAppContainerNamedObjectPath + 228
    frame #17: 0x76fa7b44 ntdll.dll`RtlGetAppContainerNamedObjectPath + 180

main.c.txt

When built with Clang it prints this before crash:

bad max_align_t size: rust: 48 (0x30) != c 24 (0x18)
bad max_align_t align: rust: 16 (0x10) != c 8 (0x8)

EDIT: It does not crash when built by Clang with max_align_t size = 24 and max_align_t align = 8