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Rollup merge of rust-lang#121573 - Enselic:sigpipe-child-process, r=M…
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…ark-Simulacrum

unix_sigpipe: Add test for SIGPIPE disposition in child processes

To make it clearer what the impact would be to stop using `SIG_IGN` and instead use a noop handler, like suggested [here](rust-lang#62569 (comment)) and implemented [here](rust-lang#121578).

Part of rust-lang#97889
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matthiaskrgr authored Mar 30, 2024
2 parents 7e0ed43 + 71eb763 commit 017a8ea
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// It is UB to unwind out of `fn start()` according to
// https://doc.rust-lang.org/beta/unstable-book/language-features/start.html so
// panic with abort to avoid UB:
//@ compile-flags: -Cpanic=abort
//@ no-prefer-dynamic so panic=abort works

#![feature(start, rustc_private)]

extern crate libc;

// Use #[start] so we don't have a runtime that messes with SIGPIPE.
#[start]
fn start(argc: isize, argv: *const *const u8) -> isize {
assert_eq!(argc, 2, "Must pass SIG_IGN or SIG_DFL as first arg");
let arg1 = unsafe { std::ffi::CStr::from_ptr(*argv.offset(1) as *const libc::c_char) }
.to_str()
.unwrap();

let expected = match arg1 {
"SIG_IGN" => libc::SIG_IGN,
"SIG_DFL" => libc::SIG_DFL,
arg => panic!("Must pass SIG_IGN or SIG_DFL as first arg. Got: {}", arg),
};

let actual = unsafe {
let mut actual: libc::sigaction = std::mem::zeroed();
libc::sigaction(libc::SIGPIPE, std::ptr::null(), &mut actual);
actual.sa_sigaction
};

assert_eq!(actual, expected, "actual and expected SIGPIPE disposition in child differs");

0
}
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//@ revisions: default sig_dfl sig_ign inherit
//@ ignore-cross-compile because aux-bin does not yet support it
//@ only-unix because SIGPIPE is a unix thing
//@ run-pass
//@ aux-bin:assert-sigpipe-disposition.rs
//@ aux-crate:sigpipe_utils=sigpipe-utils.rs

// Checks the signal disposition of `SIGPIPE` in child processes, and in our own
// process for robustness. Without any `unix_sigpipe` attribute, `SIG_IGN` is
// the default. But there is a difference in how `SIGPIPE` is treated in child
// processes with and without the attribute. Search for
// `unix_sigpipe_attr_specified()` in the code base to learn more.

#![feature(rustc_private)]
#![cfg_attr(any(sig_dfl, sig_ign, inherit), feature(unix_sigpipe))]

extern crate libc;
extern crate sigpipe_utils;

use sigpipe_utils::*;

#[cfg_attr(sig_dfl, unix_sigpipe = "sig_dfl")]
#[cfg_attr(sig_ign, unix_sigpipe = "sig_ign")]
#[cfg_attr(inherit, unix_sigpipe = "inherit")]
fn main() {
// By default we get SIG_IGN but the child gets SIG_DFL through an explicit
// reset before exec:
// https://github.com/rust-lang/rust/blob/bf4de3a874753bbee3323081c8b0c133444fed2d/library/std/src/sys/pal/unix/process/process_unix.rs#L363-L384
#[cfg(default)]
let (we_expect, child_expects) = (SignalHandler::Ignore, "SIG_DFL");

// With #[unix_sigpipe = "sig_dfl"] we get SIG_DFL and the child does too
// without any special code running before exec.
#[cfg(sig_dfl)]
let (we_expect, child_expects) = (SignalHandler::Default, "SIG_DFL");

// With #[unix_sigpipe = "sig_ign"] we get SIG_IGN and the child does too
// without any special code running before exec.
#[cfg(sig_ign)]
let (we_expect, child_expects) = (SignalHandler::Ignore, "SIG_IGN");

// With #[unix_sigpipe = "inherit"] we get SIG_DFL and the child does too
// without any special code running before exec.
#[cfg(inherit)]
let (we_expect, child_expects) = (SignalHandler::Default, "SIG_DFL");

assert_sigpipe_handler(we_expect);

assert!(
std::process::Command::new("./auxiliary/bin/assert-sigpipe-disposition")
.arg(child_expects)
.status()
.unwrap()
.success()
);
}
2 changes: 1 addition & 1 deletion tests/ui/compiletest-self-test/test-aux-bin.rs
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//@ ignore-cross-compile because we run the compiled code
//@ ignore-cross-compile because aux-bin does not yet support it
//@ aux-bin: print-it-works.rs
//@ run-pass

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