Tracking Issue for `RawOsError`

[joboet]

Feature gate: #![feature(raw_os_error_ty)]

This is a tracking issue for the raw OS error type alias, used in io::Error::raw_os_error and io::Error::from_raw_os_error (both are stable APIs).

std used to assume that the OS error type (return by errno and such) is an i32. This is however not the case on platforms like UEFI (which uses usize). To ensure idiomatic and convenient handling of native errors without loosing information, the RawOsError type is introduced to allow future ports of the standard library to use the correct error type for their respective platform. As this does not change the error type on already supported targets, this is a backwards-compatible change. Current software can still use i32 directly while the RawOsError type alias is unstable. However, this feature should probably be stabilized before ports using a different type are merged, to allow software to be more easily ported.

Public API

// std::io

pub type RawOsError = /* platform error type, `i32` most of the time */;

Steps / History

• API change proposal: Add type alias for raw OS errors libs-team#173
• Implementation: Add type alias for raw OS errors #107519
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

Footnotes

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

[GuillaumeGomez]

Just commenting on this to say that the Error::raw_os_error is stable whereas the type alias (returned by this function) isn't, which doesn't make much sense.