Repository: rust
Issue: Tracking Issue for ExitCodeExt on Windows
Labels: T-libs-api,C-tracking-issue

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Feature gate: `#![feature(windows_process_exit_code_from)]`

This is a tracking issue for implementing additional `ExitCode`s for Windows.

### Motivation

On Windows it is common for applications to return `HRESULT` (`i32`) or `DWORD` (`u32`) values. These stem from COM based components ([HRESULTS](https://docs.microsoft.com/en-us/windows/win32/api/objbase/nf-objbase-coinitialize)), Win32 errors ([GetLastError](https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror)), GUI applications ([WM_QUIT](https://docs.microsoft.com/en-us/windows/win32/winmsg/wm-quit)) and more. The newly stabilized `ExitCode` provides an excellent fit for propagating these values, because `std::process::exit` does not run deconstructors which can result in errors. However, `ExitCode` currently only implements `From<u8> for ExitCode`, which disallows the full range of `i32`/`u32` values. This pull requests attempts to address that shortcoming by providing windows specific extensions that accept a `u32` value (which covers all possible `HRESULTS` and Win32 errors) analog to [ExitStatusExt::from_raw](https://doc.rust-lang.org/std/os/windows/process/trait.ExitStatusExt.html#tymethod.from_raw).

This was also intended by the original Stabilization https://github.com/rust-lang/rust/pull/93840#issue-1129209143=  as pointed out by @eggyal in https://github.com/rust-lang/rust/issues/97914#issuecomment-1151076755:

> Issues around platform specific representations: We resolved this issue by changing the return type of report from i32 to the opaque type ExitCode. __That way we can change the underlying representation without affecting the API, letting us offer full support for platform specific exit code APIs in the future.__

[Emphasis added]

### Public API

```rust
/// Windows-specific extensions to [`process::ExitCode`].
///
/// This trait is sealed: it cannot be implemented outside the standard library.
/// This is so that future additional methods are not breaking changes.
#[stable(feature = "windows_process_exit_code_from", since = "1.63.0")]
pub trait ExitCodeExt: Sealed {
    /// Creates a new `ExitCode` from the raw underlying `u32` return value of
    /// a process.
    #[stable(feature = "windows_process_exit_code_from", since = "1.63.0")]
    fn from_raw(raw: u32) -> Self;
}

#[stable(feature = "windows_process_exit_code_from", since = "1.63.0")]
impl ExitCodeExt for process::ExitCode {
    fn from_raw(raw: u32) -> Self {
        process::ExitCode::from_inner(From::from(raw))
    }
}
```

### Steps / History

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- [x] ACP: https://github.com/rust-lang/libs-team/issues/48
- [x] Implementation: https://github.com/rust-lang/rust/pull/97917
- [x] https://github.com/rust-lang/rust/pull/118218
- [ ] Final comment period (FCP)[^1]
- [ ] Stabilization PR

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### Unresolved Questions

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- None yet.

### Additional Links

- https://github.com/rust-lang/rust/pull/93445#issue-1117891580

[^1]: https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html