Eliminate obsolete pipe2 emulation.

All supported platforms now use the native syscall.  It was added in:
* DragonflyBSD 4.2
* FreeBSD 10.0
* NetBSD 6.0
* OpenBSD 5.7

Author: asomers

CHANGELOG.md

@@ -32,6 +32,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#663](https://github.com/nix-rust/nix/pull/663))
 
 ### Changed
+- Remove obsolete `pipe2` emulation.  All supported platforms support `pipe2`
+  natively.  Users should notice no difference.
+  ([#777](https://github.com/nix-rust/nix/pull/777))
 - Renamed existing `ptrace` wrappers to encourage namespacing ([#692](https://github.com/nix-rust/nix/pull/692))
 - Marked `sys::ptrace::ptrace` as `unsafe`.
 - Changed function signature of `socket()` and `socketpair()`. The `protocol` argument

src/unistd.rs

@@ -824,10 +824,6 @@ pub fn pipe() -> Result<(RawFd, RawFd)> {
     }
 }
 
-// libc only defines `pipe2` in `libc::notbsd`.
-#[cfg(any(target_os = "linux",
-          target_os = "android",
-          target_os = "emscripten"))]
 pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
     let mut fds: [c_int; 2] = unsafe { mem::uninitialized() };
 
@@ -838,52 +834,6 @@ pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
     Ok((fds[0], fds[1]))
 }
 
-#[cfg(not(any(target_os = "linux",
-              target_os = "android",
-              target_os = "emscripten")))]
-pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
-    let mut fds: [c_int; 2] = unsafe { mem::uninitialized() };
-
-    let res = unsafe { libc::pipe(fds.as_mut_ptr()) };
-
-    try!(Errno::result(res));
-
-    try!(pipe2_setflags(fds[0], fds[1], flags));
-
-    Ok((fds[0], fds[1]))
-}
-
-#[cfg(not(any(target_os = "linux",
-              target_os = "android",
-              target_os = "emscripten")))]
-fn pipe2_setflags(fd1: RawFd, fd2: RawFd, flags: OFlag) -> Result<()> {
-    use fcntl::O_NONBLOCK;
-    use fcntl::FcntlArg::F_SETFL;
-
-    let mut res = Ok(0);
-
-    if flags.contains(O_CLOEXEC) {
-        res = res
-            .and_then(|_| fcntl(fd1, F_SETFD(FD_CLOEXEC)))
-            .and_then(|_| fcntl(fd2, F_SETFD(FD_CLOEXEC)));
-    }
-
-    if flags.contains(O_NONBLOCK) {
-        res = res
-            .and_then(|_| fcntl(fd1, F_SETFL(O_NONBLOCK)))
-            .and_then(|_| fcntl(fd2, F_SETFL(O_NONBLOCK)));
-    }
-
-    match res {
-        Ok(_) => Ok(()),
-        Err(e) => {
-            let _ = close(fd1);
-            let _ = close(fd2);
-            Err(e)
-        }
-    }
-}
-
 pub fn ftruncate(fd: RawFd, len: off_t) -> Result<()> {
     Errno::result(unsafe { libc::ftruncate(fd, len) }).map(drop)
 }

test/test_unistd.rs

@@ -2,6 +2,7 @@ extern crate tempdir;
 
 use nix::unistd::*;
 use nix::unistd::ForkResult::*;
+use nix::fcntl;
 use nix::sys::wait::*;
 use nix::sys::stat;
 use std::{env, iter};
@@ -273,3 +274,26 @@ fn test_sysconf_unsupported() {
     let open_max = sysconf(SysconfVar::_XOPEN_CRYPT);
     assert!(open_max.expect("sysconf failed").is_none())
 }
+
+// Test that we can create a pair of pipes.  No need to verify that they pass
+// data; that's the domain of the OS, not nix.
+#[test]
+fn test_pipe() {
+    let (fd0, fd1) = pipe().unwrap();
+    let m0 = stat::SFlag::from_bits_truncate(stat::fstat(fd0).unwrap().st_mode);
+    // S_IFIFO means it's a pipe
+    assert_eq!(m0, stat::S_IFIFO);
+    let m1 = stat::SFlag::from_bits_truncate(stat::fstat(fd1).unwrap().st_mode);
+    assert_eq!(m1, stat::S_IFIFO);
+}
+
+// pipe2(2) is the same as pipe(2), except it allows setting some flags.  Check
+// that we can set a flag.
+#[test]
+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));
+    let f1 = fcntl::FdFlag::from_bits_truncate(fcntl::fcntl(fd1, fcntl::F_GETFD).unwrap());
+    assert!(f1.contains(fcntl::FD_CLOEXEC));
+}