Bug: CONTEXT structure should be aligned to 16 bytes

[TimMisiak]

Which crate is this about?

windows-sys

Crate version

0.45.0

Summary

The following code will fail randomly on x86/x64 because CONTEXT is defined as DECLSPEC_ALIGN(16) in winnt.h, but does not have any alignment annotation in windows-rs.

        let hthread = unsafe { OpenThread(THREAD_ALL_ACCESS, FALSE, debug_event.dwThreadId) };

        let mut ctx: CONTEXT = unsafe { std::mem::zeroed() };
        ctx.ContextFlags = CONTEXT_ALL;
        let ret = unsafe { GetThreadContext(hthread, &mut ctx) };

Winnt.h:

typedef struct DECLSPEC_ALIGN(16) DECLSPEC_NOINITALL _CONTEXT {

Toolchain version/configuration

Default host: x86_64-pc-windows-msvc
rustup home: C:\Users\timmi.rustup

stable-x86_64-pc-windows-msvc (default)
rustc 1.67.0 (fc594f156 2023-01-24)

Reproducible example

No response

Crate manifest

[dependencies.windows-sys]
version = "0.45.0"
features = [
    "Win32_Foundation",
    "Win32_Security",
    "Win32_System_Kernel",
    "Win32_System_Threading",
    "Win32_UI_WindowsAndMessaging",
    "Win32_System_Diagnostics_Debug",
    "Win32_System_Environment",
    "Win32_System_WindowsProgramming",
]

Expected behavior

Alignment should be 16 bytes

Actual behavior

Structure has no explicit alignment, causing random failures when using it with APIs that expect alignment.

Additional comments

No response

[kennykerr]

Hi Tim, this is a known issue: #1044

I hope to bribe someone to fix this very soon. @riverar donuts are on the way.

[kennykerr]

I tried working around the issues in microsoft/windows-rs#2352 but that didn't work out. Transferring to the Win32 metadata repo, as I don't think there's anything I can do until the metadata has been fixed.

[mikebattista]

Duplicate of #1044