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Support #[unix_sigpipe = "inherit|sig_dfl"] on fn main() to prevent ignoring SIGPIPE #97802

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Merged
bors merged 5 commits into from
Sep 2, 2022
Merged

Support #[unix_sigpipe = "inherit|sig_dfl"] on fn main() to prevent ignoring SIGPIPE #97802

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ddee45e
Support `#[unix_sigpipe = "inherit|sig_dfl|sig_ign"]` on `fn main()`
Enselic Jul 5, 2022
6eae169
unix_sigpipe: Skip some tests on android; libc has no `signal` function
Enselic Aug 29, 2022
236903f
unix_sigpipe: Inline compiler sigpipe constants in std
Enselic Aug 31, 2022
3d1a4e4
unix_sigpipe: Add docs for `init()` `sigpipe` param
Enselic Aug 31, 2022
3810d4a
unix_sigpipe: Make `sigpipe` param docs long-form
Enselic Sep 1, 2022
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unix_sigpipe: Add docs for init() sigpipe param
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@Enselic
Enselic committed Aug 31, 2022
commit 3d1a4e4f2792948d78b3fed030e93c9c156fe35a
2 changes: 2 additions & 0 deletions library/std/src/rt.rs
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Expand Up @@ -72,6 +72,8 @@ macro_rules! rtunwrap {
// Runs before `main`.
// SAFETY: must be called only once during runtime initialization.
// NOTE: this is not guaranteed to run, for example when Rust code is called externally.
// The extra parameter `sigpipe` allows rustc to generate code that instructs std whether
// or not to ignore `SIGPIPE`.
#[cfg_attr(test, allow(dead_code))]
unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
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@RalfJung RalfJung Aug 31, 2022

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Would be good to have a comment here explaining the new argument (since unlike the other two it is not standard).

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@Enselic Enselic Aug 31, 2022

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Done!

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@RalfJung RalfJung Aug 31, 2022

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When just reading this file that comment remains rather mysterious though -- there are 256 possible values for sigpipe and it is unclear what they would all mean.

Looks like the concrete meaning is platform-dependent? That should be said, maybe with a reference to the file where unix defines its meanings.

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@RalfJung RalfJung Aug 31, 2022

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Ah no actually compiler/rustc_session/src/config/sigpipe.rs is not target-dependent. So that should probably be referenced.

But then I don't understand why the std version of that file is inside unix.

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@Enselic Enselic Aug 31, 2022

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@RalfJung If you would like to have more of a "full context" kind of doc at this location, that's perfectly fine with me. Would you mind us iterating the exact contents of that comment via GitHub comments rather than commits though?

Here is my proposal on what we could write here:

// # The `sigpipe` parameter
//
// Since 2014, the Rust runtime on Unix has set the `SIGPIPE` handler to
// `SIG_IGN`. Applications have good reasons to want a different behavior
// though, so there is a `#[unix_sigpipe = "..."]` attribute on `fn main()` that
// can be used to select how `SIGPIPE` shall be setup (if changed at all) before
// `fn main()` is called. See <https://github.com/rust-lang/rust/issues/97889>
// for more info.
//
// The `sigpipe` parameter to this function gets its value via the code that
// rustc generates to invoke `fn lang_start()`. The reason we have `sigpipe` for
// all platforms and not only Unix, is because std is not allowed to have `cfg`
// directives as this high level. See the module docs in
// `src/tools/tidy/src/pal.rs` for more info. On all other platforms, `sigpipe`
// has a value, but its value is ignored.
//
// Even though it is an `u8`, it only ever has 3 values. These are documented in
// `compiler/rustc_session/src/config/sigpipe.rs`.

I propose that we do not duplicate this comment also in library/std/src/sys/unix/mod.rs though, i.e. that we only put that comment at the location you made this comment.

Looking forward to your response.

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@RalfJung RalfJung Aug 31, 2022

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Yeah that sounds good! I don't have a strong preference whether library/std/src/rt.rs points to library/std/src/sys/unix/mod.rs or vice versa.

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@Enselic Enselic Sep 1, 2022

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Great! Commit pushed.

unsafe {
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2 changes: 2 additions & 0 deletions library/std/src/sys/unix/mod.rs
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Expand Up @@ -49,6 +49,8 @@ pub fn init(argc: isize, argv: *const *const u8, _sigpipe: u8) {}
#[cfg(not(target_os = "espidf"))]
// SAFETY: must be called only once during runtime initialization.
// NOTE: this is not guaranteed to run, for example when Rust code is called externally.
// The extra parameter `sigpipe` allows rustc to generate code that instructs std whether
// or not to ignore `SIGPIPE`.
pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
// The standard streams might be closed on application startup. To prevent
// std::io::{stdin, stdout,stderr} objects from using other unrelated file
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