fix fault when shutdown called before start on Thread or Worker

package.xml

@@ -13,20 +13,16 @@
  <date>2015-11-20</date>
  <time>11:00:00</time>
  <version>
-  <release>3.1.0</release>
-  <api>3.1.0</api>
+  <release>3.1.1</release>
+  <api>3.1.1</api>
  </version>
  <stability>
   <release>stable</release>
   <api>stable</api>
  </stability>
  <license uri="http://www.php.net/license">PHP License</license>
  <notes>
- Initial development of v3 is complete, this release is the first supported
- release of pthreads v3 for PHP7.
- Breaking changes for Collectables in this release.
- SemVer will be (roughly) followed from this release onward.
- Everyone on PHP7 must upgrade!
+ Fix fault when ::shutdown is called on Thread preceeding ::start
  </notes>
  <contents>
   <dir name="/">
@@ -128,6 +124,7 @@
 	<file name="tests/workers-default-collector.phpt" role="test" />
 	<file name="tests/workers-no-collect.phpt" role="test" />
 	<file name="tests/workers-no-join.phpt" role="test" />
+	<file name="tests/workers-no-shutdown-before-start.phpt" role="test" />
 	<file name="tests/workers-no-stack.phpt" role="test" />
 	<file name="tests/workers-no-start.phpt" role="test" />
 	<file name="tests/workers-no-unstack.phpt" role="test" />

src/object.c

@@ -412,6 +412,13 @@ zend_bool pthreads_join(pthreads_object_t* thread) {
 		return 0;
 	}
 
+	if (!pthreads_monitor_check(thread->monitor, PTHREADS_MONITOR_STARTED)) {
+		zend_throw_exception_ex(spl_ce_RuntimeException, 0,
+			"%s has not been started",
+			thread->std.ce->name->val);
+		return 0;
+	}
+
 	pthreads_monitor_add(thread->monitor, PTHREADS_MONITOR_JOINED);
 
 	return (pthread_join(thread->thread, NULL) == SUCCESS);

tests/workers-no-shutdown-before-start.phpt

@@ -0,0 +1,22 @@
+--TEST--
+Test pthreads Worker::shutdown
+--DESCRIPTION--
+This test verifies shutdown of a Worker (or Thread) not yet started doesn't fault
+--FILE--
+<?php
+$worker = new Worker();
+
+$worker->stack(new class extends Threaded {
+	public function run() {
+		var_dump($this);
+	}
+});
+
+$worker->shutdown();
+?>
+--EXPECTF--
+Fatal error: Uncaught RuntimeException: Worker has not been started in %s:10
+Stack trace:
+#0 %s(10): Worker->shutdown()
+#1 {main}
+  thrown in %s on line 10

tests/workers-ok-unstack.phpt

@@ -4,7 +4,6 @@ Test pthreads Worker::unstack
 This test verifies that unstack functions as intended
 --FILE--
 <?php
-
 $worker = new Worker();
 
 $worker->stack(new class extends Threaded {
@@ -14,8 +13,6 @@ $worker->stack(new class extends Threaded {
 });
 
 var_dump($worker->unstack());
-
-$worker->shutdown();
 ?>
 --EXPECTF--
 object(class@anonymous)#%d (%d) {