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Use less syscalls in anon_pipe() #39386

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Merged
bors merged 2 commits into from
Feb 2, 2017
Merged

Use less syscalls in anon_pipe() #39386

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c31d5b5
Use less syscalls in `anon_pipe()`
tbu- Jan 27, 2017
4b46d2a
Don't handle ENOSYS in `anon_pipe()`
tbu- Jan 30, 2017
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38 changes: 19 additions & 19 deletions src/libstd/sys/unix/pipe.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,8 @@ use io;
use libc::{self, c_int};
use mem;
use ptr;
use sys::cvt_r;
use sync::atomic::{AtomicBool, Ordering};
use sys::{cvt, cvt_r};
use sys::fd::FileDesc;

////////////////////////////////////////////////////////////////////////////////
Expand All @@ -29,34 +30,33 @@ pub fn anon_pipe() -> io::Result<(AnonPipe, AnonPipe)> {
// CLOEXEC flag is to use the `pipe2` syscall on Linux. This was added in
// 2.6.27, however, and because we support 2.6.18 we must detect this
// support dynamically.
if cfg!(target_os = "linux") {
static TRY_PIPE2: AtomicBool = AtomicBool::new(cfg!(target_os = "linux"));
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@nagisa nagisa Jan 29, 2017 •
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Preexisting:

pipe2 is also supported on freebsd (>= 10.0), netbsd (>= 6.0), dragonflybsd (appeared ~4.0-ish?), openbsd (>= 5.7). These probably should also appear in that cfg! above.

if TRY_PIPE2.load(Ordering::Relaxed) {
weak! { fn pipe2(*mut c_int, c_int) -> c_int }
if let Some(pipe) = pipe2.get() {
match cvt_r(|| unsafe { pipe(fds.as_mut_ptr(), libc::O_CLOEXEC) }) {
Ok(_) => {
match cvt(unsafe { pipe(fds.as_mut_ptr(), libc::O_CLOEXEC) }) {
Err(ref e) if e.raw_os_error() == Some(libc::ENOSYS) => {
TRY_PIPE2.store(false, Ordering::Relaxed);
// Fall through
},
res => {
res?;
return Ok((AnonPipe(FileDesc::new(fds[0])),
AnonPipe(FileDesc::new(fds[1]))))
AnonPipe(FileDesc::new(fds[1]))));
}
Err(ref e) if e.raw_os_error() == Some(libc::ENOSYS) => {}
Err(e) => return Err(e),
}
}
}
if unsafe { libc::pipe(fds.as_mut_ptr()) == 0 } {
let fd0 = FileDesc::new(fds[0]);
let fd1 = FileDesc::new(fds[1]);
Ok((AnonPipe::from_fd(fd0)?, AnonPipe::from_fd(fd1)?))
} else {
Err(io::Error::last_os_error())
}
cvt(unsafe { libc::pipe(fds.as_mut_ptr()) })?;

let fd0 = FileDesc::new(fds[0]);
let fd1 = FileDesc::new(fds[1]);
fd0.set_cloexec()?;
fd1.set_cloexec()?;
Ok((AnonPipe(fd0), AnonPipe(fd1)))
}

impl AnonPipe {
pub fn from_fd(fd: FileDesc) -> io::Result<AnonPipe> {
fd.set_cloexec()?;
Ok(AnonPipe(fd))
}

pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
self.0.read(buf)
}
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