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Re: Differences between container used by "guix build" and "guix environ
From: |
Danny Milosavljevic |
Subject: |
Re: Differences between container used by "guix build" and "guix environment -C -N" |
Date: |
Mon, 19 Jun 2017 20:58:08 +0200 |
Hi Ludo,
it does pretty much the equvalent of this Python program, in Rust:
------------------------
#!/usr/bin/env python3
import os
import subprocess
import signal
signal.pthread_sigmask(signal.SIG_BLOCK, [signal.SIGINT])
p = subprocess.Popen(["cat"], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
signal.pthread_sigmask(signal.SIG_UNBLOCK, [signal.SIGINT])
os.kill(p.pid, signal.SIGINT)
stdout, stderr = p.communicate(b"hello\n", timeout=1)
assert stdout == b""
p.wait()
------------------------
The goal of it is to test this feature: Their "Popen" implementation uses
something like spawnvp, only they have overwritten it in order to clear the
signal mask for the child.
In Rust the test is:
------------------------------------------------------
fn test_process_mask() {
unsafe {
// Test to make sure that a signal mask does not get inherited.
let mut cmd = Command::new(OsStr::new("cat"));
let mut set: libc::sigset_t = mem::uninitialized();
let mut old_set: libc::sigset_t = mem::uninitialized();
t!(cvt(libc::sigemptyset(&mut set)));
t!(cvt(sigaddset(&mut set, libc::SIGINT)));
t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &set, &mut
old_set)));
cmd.stdin(Stdio::MakePipe);
cmd.stdout(Stdio::MakePipe);
let (mut cat, mut pipes) = t!(cmd.spawn(Stdio::Null, true));
let stdin_write = pipes.stdin.take().unwrap();
let stdout_read = pipes.stdout.take().unwrap();
t!(cvt(libc::pthread_sigmask(libc::SIG_SETMASK, &old_set,
ptr::null_mut())));
t!(cvt(libc::kill(cat.id() as libc::pid_t, libc::SIGINT)));
// We need to wait until SIGINT is definitely delivered. The
// easiest way is to write something to cat, and try to read it
// back: if SIGINT is unmasked, it'll get delivered when cat is
// next scheduled.
let _ = stdin_write.write(b"Hello");
drop(stdin_write);
// Either EOF or failure (EPIPE) is okay.
let mut buf = [0; 5];
if let Ok(ret) = stdout_read.read(&mut buf) {
assert!(ret == 0);
}
t!(cat.wait());
}
------------------------------------------------------
and the implementation that clears the mask is
https://github.com/rust-lang/rust/blob/1.16.0/src/libstd/sys/unix/process/process_unix.rs#L144
(line 144ff, bottom of "fn do_exec")