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Use the real pipe2(2) on most targets #777

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Dec 8, 2017
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@asomers asomers commented Oct 8, 2017

FreeBSD added pipe2(2) in version 10.0.

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This needs an Added CHANGELOG entry and could also use comments for the tests.

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Does it even make sense to keep the bind2() emulation around if according to libc pip2 exists on android, emscripten, and linux?

src/unistd.rs Outdated
@@ -827,7 +827,8 @@ pub fn pipe() -> Result<(RawFd, RawFd)> {
// libc only defines `pipe2` in `libc::notbsd`.
#[cfg(any(target_os = "linux",
target_os = "android",
target_os = "emscripten"))]
target_os = "emscripten",
target_os = "freebsd"))]
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Since you're here, can you reorder the OSes to be alphabetical?

src/unistd.rs Outdated
@@ -840,7 +841,8 @@ pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {

#[cfg(not(any(target_os = "linux",
target_os = "android",
target_os = "emscripten")))]
target_os = "emscripten",
target_os = "freebsd")))]
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Same here.

src/unistd.rs Outdated
@@ -855,7 +857,8 @@ pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {

#[cfg(not(any(target_os = "linux",
target_os = "android",
target_os = "emscripten")))]
target_os = "emscripten",
target_os = "freebsd")))]
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And here.

src/unistd.rs Outdated
@@ -827,7 +827,8 @@ pub fn pipe() -> Result<(RawFd, RawFd)> {
// libc only defines `pipe2` in `libc::notbsd`.
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Can you clean up this comment? Seems out of date since freebsd support is being added.

Additionally, it appears that this is supported by NetBSD and OpenBSD according to libc, so let's add support for bind2 on those platforms as well.

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I didn't check those platforms. It looks like pretty much everything supports it now, even Illumos.

CHANGELOG.md Outdated
@@ -32,6 +32,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
([#663](https://github.com/nix-rust/nix/pull/663))

### Changed
- On FreeBSD, bind directly to `pipe2` instead of emulating it. Users should
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Since we tell the user they'll notice no difference, I think it'd be good to say why we're doing this. I'm not certain why we were emulating this in the first place, so that could be clarified here.

Also, this should be updated for NetBSD and OpenBSD also.

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Looks like it needs a rebase and I'm not certain why testing failed, let's give it another run.

@Susurrus Susurrus changed the title Use the real pipe2(2) on FreeBSD Use the real pipe2(2) on all targets Oct 20, 2017
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Needs a rebase then I'm r+ on it.

@asomers asomers added this to the 0.10.0 milestone Nov 5, 2017
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Susurrus commented Nov 6, 2017

Looks like Darwin doesn't support it or it's just not implemented in libc yet, which is why testing fails.

Also, it'd be good if you added doccomments for pipe2 as part of this work since you're touching the function already and it's missing that.

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Note that pipe2 doesn't exist on Mac, so this will need to be restricted from those targets.

@asomers asomers changed the title Use the real pipe2(2) on all targets Use the real pipe2(2) on most targets Nov 19, 2017
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asomers commented Nov 19, 2017

Oops, I forgot to update doc comments. I'll do that shortly.

fn test_pipe2() {
let (fd0, fd1) = pipe2(fcntl::O_CLOEXEC).unwrap();
let f0 = fcntl::FdFlag::from_bits_truncate(fcntl::fcntl(fd0, fcntl::F_GETFD).unwrap());
assert!(f0.contains(fcntl::FD_CLOEXEC));
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Shouldn't you check that both of these fds don't have this flag to begin with?

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What do you mean "to begin with"? pipe2 sets that flag atomically as the pipe is created.

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You're correct, ignore this comment.

src/unistd.rs Outdated
/// `O_CLOEXEC`: Set the close-on-exec flag for the new file descriptors.
/// `O_NONBLOCK`: Set the non-blocking flag for the ends of the pipe.
#[cfg(any(target_os = "ios",
target_os = "macos"))]
pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
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Does it make sense to keep this emulation for just ios/macos? We've removed emulated functionality before, and I'd like to suggest we remove it here as well.

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Removing it would make me happy. But perhaps we should mark it as deprecated for a release cycle first?

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Sure, let's mark it deprecated for 0.10 and then remove for the next release.

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asomers commented Nov 22, 2017

This is unusual. The build failures in Travis were caused by a merge error. Travis's merge error. Travis pulled the master branch then tried to apply my patch, and it looks like it duped a line. I'll rebase.

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Susurrus commented Dec 3, 2017

bors r+

bors bot added a commit that referenced this pull request Dec 3, 2017
777: Use the real pipe2(2) on most targets r=Susurrus a=asomers

FreeBSD added pipe2(2) in version 10.0.
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bors bot commented Dec 3, 2017

Build failed

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Susurrus commented Dec 3, 2017

Ahh, yes. Tests need to be updated because #801 was merged.

src/unistd.rs Outdated
#[cfg(not(any(target_os = "linux",
target_os = "android",
target_os = "emscripten")))]
#[cfg(any(target_os = "ios",
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This should be just 1 line.

src/unistd.rs Outdated
///
/// `O_CLOEXEC`: Set the close-on-exec flag for the new file descriptors.
/// `O_NONBLOCK`: Set the non-blocking flag for the ends of the pipe.
#[cfg(any(target_os = "ios",
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Should just be 1 line also.

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I think it's just the CHANGELOG fix and then this LGTM.

CHANGELOG.md Outdated
@@ -47,6 +47,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
([#800](https://github.com/nix-rust/nix/pull/800))

### Changed
- Use native `pipe` on all BSD targets. Users should notice no difference.
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Don't you actually mean pipe2 here?

All supported non-Apple platforms now use the native syscall.  Only ios
and macos lack it.  Deprecate pipe2 on those platforms, because it's
impossible to guarantee atomicity with a userland implementation.  It
was added in:
* DragonflyBSD 4.2
* FreeBSD 10.0
* NetBSD 6.0
* OpenBSD 5.7
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asomers commented Dec 8, 2017

bors r+ susurrus

bors bot added a commit that referenced this pull request Dec 8, 2017
777: Use the real pipe2(2) on most targets r=asomers a=asomers

FreeBSD added pipe2(2) in version 10.0.
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Susurrus commented Dec 8, 2017

Probably should have added that we deprecated our wrapper on other platforms in the CHANGELOG as well.

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bors bot commented Dec 8, 2017

@bors bors bot merged commit 6c939fb into nix-rust:master Dec 8, 2017
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