Regression: File::open not falling back to FileEndOfFileInfo on WINE

[MeguminSama]

As of what appears to be this commit ca56dc8, nightly crashes on WINE when running File::open.

The issue appears to be that SetFileInformationByHandle returns 0 when it fails, and expects you to run GetLastError to get the error code.

In the code for File::open, there is a comment block explaining that this should fall back to using FileEndOfFileInfo if it fails, for WINE support.

rust/library/std/src/sys/pal/windows/fs.rs

Lines 319 to 322 in cd805f0

	// This first tries `FileAllocationInfo` but falls back to
	// `FileEndOfFileInfo` in order to support WINE.
	// If WINE gains support for FileAllocationInfo, we should
	// remove the fallback.

However from this commit, the code will panic if the result of api::get_last_error().code != 0, meaning it will always panic if FileAllocationInfo fails, and will never attempt to use FileEndOfFileInfo.

Relevant source code:

rust/library/std/src/sys/pal/windows/fs.rs

Lines 331 to 340 in cd805f0

	if api::get_last_error().code != 0 {
	panic!("FILE_ALLOCATION_INFO failed!!!");
	}
	let eof = c::FILE_END_OF_FILE_INFO { EndOfFile: 0 };
	let result = c::SetFileInformationByHandle(
	handle.as_raw_handle(),
	c::FileEndOfFileInfo,
	(&raw const eof).cast::<c_void>(),
	mem::size_of::<c::FILE_END_OF_FILE_INFO>() as u32,
	);

I tried this code:

fn main() {
    std::fs::write("testing.txt", "Hello world").unwrap();
}

I expected to see this happen: Hello world should be written to testing.txt

Instead, this happened: Rust panics with a backtrace.

Meta

rustc --version --verbose:

rustc 1.86.0-nightly (f3d1d47fd 2025-01-20)
binary: rustc
commit-hash: f3d1d47fd84dfcf7f513be1dbad356e74c8f3b2b
commit-date: 2025-01-20
host: x86_64-unknown-linux-gnu
release: 1.86.0-nightly
LLVM version: 19.1.7

This does not occur on stable. Reverting to nightly-2024-12-23 also works fine.

Backtrace

cargo xwin run --target x86_64-pc-windows-msvc
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.00s
     Running `wine target/x86_64-pc-windows-msvc/debug/rusttest.exe`
wineserver: using server-side synchronization.
wine: Using setpriority to control niceness in the [-10,10] range

thread 'main' panicked at library\std\src\sys\pal\windows\fs.rs:332:29:
FILE_ALLOCATION_INFO failed!!!
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[ChrisDenton]

Oh apologies it seems I left in some test code somehow. That panic message was definitely not meant to make it in to production.

[MeguminSama]

No worries, thanks for responding so quickly :)