FreeBSD: add pthread_getthreadid_np() (#2725)

* FreeBSD: add implementation for process::pthread_getthreadid_np()

* FreeBSD: enable unistd::pthread_getthreadid_np() test

Author: kostikbel

changelog/2725.added.md

@@ -0,0 +1 @@
+Added process::pthread_getthreadid_np() on FreeBSD.

src/unistd.rs

@@ -403,6 +403,14 @@ pub fn getpgrp() -> Pid {
 pub fn gettid() -> Pid {
     Pid(unsafe { libc::syscall(libc::SYS_gettid) as pid_t })
 }
+
+/// Get the caller's thread ID (see
+/// [pthread_getthreadid_np(3)](https://man.freebsd.org/cgi/man.cgi?query=pthread_getthreadid_np&sektion=3&manpath=FreeBSD+15.0-RELEASE+and+Ports).
+#[cfg(target_os = "freebsd")]
+#[inline]
+pub fn pthread_getthreadid_np() -> Pid {
+    Pid(unsafe { libc::pthread_getthreadid_np() as pid_t })
+}
 }
 
 feature! {

test/test_unistd.rs

@@ -260,6 +260,19 @@ mod linux_android {
     }
 }
 
+#[cfg(target_os = "freebsd")]
+mod freebsd {
+    use nix::unistd::pthread_getthreadid_np;
+
+    #[test]
+    fn test_pthread_getthreadid_np() {
+        let tid: ::libc::pid_t = pthread_getthreadid_np().into();
+        // FreeBSD has thread id namespace shared with pids, the split
+        // is at PID_MAX = 99999.
+        assert!(tid >= 100000);
+    }
+}
+
 #[test]
 // `getgroups()` and `setgroups()` do not behave as expected on Apple platforms
 #[cfg(not(any(