Fix child_process.kill oddities

* When the process is already dead, but the `exit` signal wasn't raised
  yet, the ESRCH error should be ignored.

* When an invalid signal is specified, kill() should throw.

* Like process.kill(), child_process.kill() now preserves a `0` signal
  which can be used to check the liveliness of the child process.

* process.kill() and child_process.kill() will now return true if the
  signal was actually delivered, and false otherwise.

* When an `exec`-ed process is automatically killed because a time or
  buffer limit is exceeded, and the kill() fails, this error should be
  reported through the `exec` callback.

Fixes: #3409

lib/child_process.js

@@ -536,12 +536,24 @@ exports.execFile = function(file /* args, options, callback */) {
     }
   }
 
+  function errorhandler(e) {
+    err = e;
+    child.stdout.destroy();
+    child.stderr.destroy();
+    exithandler();
+  }
+
   function kill() {
+    child.stdout.destroy();
+    child.stderr.destroy();
+
     killed = true;
-    child.kill(options.killSignal);
-    process.nextTick(function() {
-      exithandler(null, options.killSignal);
-    });
+    try {
+      child.kill(options.killSignal);
+    } catch (e) {
+      err = e;
+      exithandler();
+    }
   }
 
   if (options.timeout > 0) {
@@ -571,6 +583,7 @@ exports.execFile = function(file /* args, options, callback */) {
   });
 
   child.addListener('close', exithandler);
+  child.addListener('error', errorhandler);
 
   return child;
 };
@@ -822,25 +835,43 @@ function errnoException(errorno, syscall, errmsg) {
 
 
 ChildProcess.prototype.kill = function(sig) {
+  var signal;
+
   if (!constants) {
     constants = process.binding('constants');
   }
 
-  sig = sig || 'SIGTERM';
-  var signal = constants[sig];
+  if (sig === 0) {
+    signal = 0;
+  } else if (!sig) {
+    signal = constants['SIGTERM'];
+  } else {
+    signal = constants[sig];
+  }
 
-  if (!signal) {
+  if (signal === undefined) {
     throw new Error('Unknown signal: ' + sig);
   }
 
   if (this._handle) {
-    this.killed = true;
     var r = this._handle.kill(signal);
-    if (r === -1) {
+    if (r == 0) {
+      /* Success. */
+      this.killed = true;
+      return true;
+    } else if (errno == 'ESRCH') {
+      /* Already dead. */
+    } else if (errno == 'EINVAL' || errno == 'ENOSYS') {
+      /* The underlying platform doesn't support this signal. */
+      throw errnoException(errno, 'kill');
+    } else {
+      /* Other error, almost certainly EPERM. */
       this.emit('error', errnoException(errno, 'kill'));
-      return;
     }
   }
+
+  /* Kill didn't succeed. */
+  return false;
 };
 
 

src/node.js

@@ -430,6 +430,8 @@
       if (r) {
         throw errnoException(errno, 'kill');
       }
+
+      return true;
     };
   };