support gettid on macos

CHANGELOG.md

@@ -6,6 +6,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased]
 
 ### Added
+- Added `nix::sys::pthread::pthread_self`
+  ([#591](https://github.com/nix-rust/nix/pull/591)
 - Added `AioCb::from_boxed_slice`
   ([#582](https://github.com/nix-rust/nix/pull/582)
 - Added `nix::unistd::{openat, fstatat, readlink, readlinkat}`

src/sys/mod.rs

@@ -84,3 +84,4 @@ pub mod statfs;
               target_arch = "arm")),
           )]
 pub mod statvfs;
+pub mod pthread;

src/sys/pthread.rs

@@ -0,0 +1,11 @@
+use libc::{self, pthread_t};
+
+/// Obtain ID of the calling thread (see
+/// [pthread_self(3)](http://man7.org/linux/man-pages/man3/pthread_self.3.html)
+///
+/// The thread ID returned by pthread_self() is not the same thing as
+/// the kernel thread ID returned by a call to gettid(2).
+#[inline]
+pub fn pthread_self() -> pthread_t {
+    unsafe { libc::pthread_self() }
+}

test/sys/mod.rs

@@ -12,3 +12,4 @@ mod test_uio;
 
 #[cfg(target_os = "linux")]
 mod test_epoll;
+mod test_pthread;

test/sys/test_pthread.rs

@@ -0,0 +1,7 @@
+use nix::sys::pthread::*;
+
+#[test]
+fn test_pthread_self() {
+    let tid = pthread_self();
+    assert!(tid > 0);
+}