Merge pull request #365 from mitchellh/goonz/fix-zomby-subprocesses

termio/exec: don't leak zombie subprocesses

src/Command.zig

@@ -187,10 +187,20 @@ fn setupFd(src: File.Handle, target: i32) !void {
 
 /// Wait for the command to exit and return information about how it exited.
 pub fn wait(self: Command, block: bool) !Exit {
-    // We specify NOHANG because its not our fault if the process we launch
-    // for the tty doesn't properly waitpid its children. We don't want
-    // to hang the terminal over it.
-    const res = std.os.waitpid(self.pid.?, if (block) 0 else std.c.W.NOHANG);
+    const res = if (block) std.os.waitpid(self.pid.?, 0) else res: {
+        // We specify NOHANG because its not our fault if the process we launch
+        // for the tty doesn't properly waitpid its children. We don't want
+        // to hang the terminal over it.
+        // When NOHANG is specified, waitpid will return a pid of 0 if the process
+        // doesn't have a status to report. When that happens, it is as though the
+        // wait call has not been performed, so we need to keep trying until we get
+        // a non-zero pid back, otherwise we end up with zombie processes.
+        while (true) {
+            const res = std.os.waitpid(self.pid.?, std.c.W.NOHANG);
+            if (res.pid != 0) break :res res;
+        }
+    };
+
     return Exit.init(res.status);
 }
 

src/termio/Exec.zig

@@ -831,8 +831,9 @@ const Subprocess = struct {
     }
 
     /// Stop the subprocess. This is safe to call anytime. This will wait
-    /// for the subprocess to end so it will block. This does not close
-    /// the pty.
+    /// for the subprocess to register that it has been signalled, but not
+    /// for it to terminate, so it will not block.
+    /// This does not close the pty.
     pub fn stop(self: *Subprocess) void {
         // Kill our command
         if (self.command) |*cmd| {