Tracking Issue for stdin/stdout/stderr file descriptor constants

[hanna-kruppe]

Feature gate: #![feature(stdio_fd_consts)]

This is a tracking issue for BorrowedFd<'static> constants for stdin, stdout and stderr.

This feature enables I/O-safe access to the stdio file descriptors without touching the higher-level std::io handles and their locks.

Public API

// std::os::fd

const STDIN: BorrowedFd<'static>;
const STDOUT: BorrowedFd<'static>;
const STDERR: BorrowedFd<'static>;

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: Guarantee direct access to std{in,out,err} file descriptors as BorrowedFd<'static> libs-team#719
• Implementation: Implement stdio FD constants #152071
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

Footnotes

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

[bjorn3]

std::io::{Stdin, Stdout, Stderr}.as_fd() doesn't take a lock, nor does the Windows counterpart.

[hanna-kruppe]

The ACP discusses why AsFd is not sufficient for all use cases despite not currently taking a lock itself.

Another problem not mentioned there (because I mostly care about stderr) is how you get your hands on the StdFoo object in the first place. std::io::stdout() uses another lock internally to initialize the buffer on first access, the other constructors may also do that if std ever adds configurable buffering or other niceties for those handles.