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use std;
use std::io;
use std::process::Child;
// A handle on Unix is just the PID.
pub struct Handle(u32);
pub fn get_handle(child: &Child) -> Handle {
Handle(child.id())
}
// This blocks until a child exits, without reaping the child.
pub fn wait_without_reaping(handle: Handle) -> io::Result<()> {
loop {
let ret = unsafe {
let mut siginfo = std::mem::zeroed();
libc::waitid(
libc::P_PID,
handle.0 as libc::id_t,
&mut siginfo,
libc::WEXITED | libc::WNOWAIT,
)
};
if ret == 0 {
return Ok(());
}
let error = io::Error::last_os_error();
if error.kind() != io::ErrorKind::Interrupted {
return Err(error);
}
// We were interrupted. Loop and retry.
}
}
// This checks whether the child has already exited, without reaping the child.
pub fn try_wait_without_reaping(handle: Handle) -> io::Result<bool> {
let mut siginfo: libc::siginfo_t;
let ret = unsafe {
// Darwin doesn't touch the siginfo_t struct if the child hasn't exited
// yet. It expects us to have zeroed it ahead of time:
//
// The state of the siginfo structure in this case
// is undefined. Some implementations bzero it, some
// (like here) leave it untouched for efficiency.
//
// Thus the most portable check for "no matching pid with
// WNOHANG" is to store a zero into si_pid before
// invocation, then check for a non-zero value afterwards.
//
// https://github.com/opensource-apple/xnu/blob/0a798f6738bc1db01281fc08ae024145e84df927/bsd/kern/kern_exit.c#L2150-L2156
//
// XXX: The siginfo_t struct has padding. Does that make it unsound to
// initialize it this way?
siginfo = std::mem::zeroed();
libc::waitid(
libc::P_PID,
handle.0 as libc::id_t,
&mut siginfo,
libc::WEXITED | libc::WNOWAIT | libc::WNOHANG,
)
};
if ret != 0 {
// EINTR should be impossible here
Err(io::Error::last_os_error())
} else if siginfo.si_signo == libc::SIGCHLD {
// The child has exited.
Ok(true)
} else if siginfo.si_signo == 0 {
// The child has not exited.
Ok(false)
} else {
// This should be impossible if we called waitid correctly. But it will
// show up on macOS if we forgot to zero the siginfo_t above, for example.
Err(io::Error::new(
io::ErrorKind::Other,
format!("unexpected si_signo from waitid: {}", siginfo.si_signo),
))
}
}