Fix signal handler in NativeDriver when used with pcntl_async_signals

Fixes #264.

lib/Loop/NativeDriver.php

@@ -2,6 +2,7 @@
 
 namespace Amp\Loop;
 
+use Amp\CallableMaker;
 use Amp\Coroutine;
 use Amp\Promise;
 use React\Promise\PromiseInterface as ReactPromise;
@@ -10,6 +11,8 @@ use function Amp\Promise\rethrow;
 
 class NativeDriver extends Driver
 {
+    use CallableMaker;
+
     /** @var resource[] */
     private $readStreams = [];
 
@@ -297,7 +300,7 @@ class NativeDriver extends Driver
 
                 case Watcher::SIGNAL:
                     if (!isset($this->signalWatchers[$watcher->value])) {
-                        if (!@\pcntl_signal($watcher->value, [$this, 'handleSignal'])) {
+                        if (!@\pcntl_signal($watcher->value, $this->callableFromInstanceMethod('handleSignal'))) {
                             $message = "Failed to register signal handler";
                             if ($error = \error_get_last()) {
                                 $message .= \sprintf("; Errno: %d; %s", $error["type"], $error["message"]);

test/Loop/NativeDriverTest.php

@@ -2,6 +2,7 @@
 
 namespace Amp\Test\Loop;
 
+use Amp\Loop\Driver;
 use Amp\Loop\NativeDriver;
 
 class NativeDriverTest extends DriverTest
@@ -17,4 +18,28 @@ class NativeDriverTest extends DriverTest
     {
         $this->assertNull($this->loop->getHandle());
     }
+
+    /**
+     * @requires PHP 7.1
+     */
+    public function testAsyncSignals()
+    {
+        \pcntl_async_signals(true);
+
+        try {
+            $this->start(function (Driver $loop) use (&$invoked) {
+                $watcher = $loop->onSignal(SIGUSR1, function () use (&$invoked) {
+                    $invoked = true;
+                });
+                $loop->unreference($watcher);
+                $loop->defer(function () {
+                    \posix_kill(\getmypid(), \SIGUSR1);
+                });
+            });
+        } finally {
+            \pcntl_async_signals(false);
+        }
+
+        $this->assertTrue($invoked);
+    }
 }