Use the real pipe2(2) on FreeBSD

FreeBSD added pipe2(2) in version 10.0.

CHANGELOG.md

@@ -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
+  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

@@ -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"))]
 pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
     let mut fds: [c_int; 2] = unsafe { mem::uninitialized() };
 
@@ -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")))]
 pub fn pipe2(flags: OFlag) -> Result<(RawFd, RawFd)> {
     let mut fds: [c_int; 2] = unsafe { mem::uninitialized() };
 
@@ -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")))]
 fn pipe2_setflags(fd1: RawFd, fd2: RawFd, flags: OFlag) -> Result<()> {
     use fcntl::O_NONBLOCK;
     use fcntl::FcntlArg::F_SETFL;

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));
+}