Add a convenience method .pid() for WaitStatus.

Author: marmistrz

src/sys/wait.rs

@@ -93,6 +93,25 @@ pub enum WaitStatus {
     StillAlive
 }
 
+impl WaitStatus {
+    /// Extracts the PID from the WaitStatus if the status is not StillAlive.
+    pub fn pid(&self) -> Option<Pid> {
+        use self::WaitStatus::*;
+        match self {
+            &Exited(p, _) => Some(p),
+            &Signaled(p, _, _) => Some(p),
+            &Stopped(p, _) => Some(p),
+            &Continued(p) => Some(p),
+            &StillAlive => None,
+
+            #[cfg(any(target_os = "linux", target_os = "android"))]
+            &PtraceEvent(p, _, _) => Some(p),
+            #[cfg(any(target_os = "linux", target_os = "android"))]
+            &PtraceSyscall(p) => Some(p),
+        }
+    }
+}
+
 #[cfg(any(target_os = "linux",
           target_os = "android"))]
 mod status {

test/sys/test_wait.rs

@@ -37,6 +37,19 @@ fn test_wait_exit() {
     }
 }
 
+#[test]
+fn test_waitstatus_pid() {
+    let _m = ::FORK_MTX.lock().expect("Mutex got poisoned by another test");
+
+    match fork().unwrap() {
+        Child => {},
+        Parent { child } => {
+            let status = waitpid(child, None).unwrap();
+            assert_eq!(status.pid(), Some(child));
+        }
+    }
+}
+
 #[cfg(any(target_os = "linux", target_os = "android"))]
 // FIXME: qemu-user doesn't implement ptrace on most arches
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
@@ -47,7 +60,7 @@ mod ptrace {
     use nix::sys::wait::*;
     use nix::unistd::*;
     use nix::unistd::ForkResult::*;
-    use std::{ptr, process};
+    use std::ptr;
     use libc::_exit;
 
     fn ptrace_child() -> ! {