gstpad, gstobject: Add GMutexLocker helper

Add GST_OBJECT_AUTO_LOCK() and GST_PAD_STREAM_AUTO_LOCK() to simplify
g_autoptr(GMutexLocker) usage.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4300>

subprojects/gstreamer/gst/gstobject.h

@@ -88,6 +88,34 @@ typedef enum
  * It blocks until the lock can be obtained.
  */
 #define GST_OBJECT_LOCK(obj)                   g_mutex_lock(GST_OBJECT_GET_LOCK(obj))
+
+/**
+ * GST_OBJECT_AUTO_LOCK:
+ * @obj: a #GstObject to lock
+ * @var: a variable name to be declared
+ *
+ * Declare a #GMutexLocker variable with g_autoptr() and lock the object. The
+ * mutex will be unlocked automatically when leaving the scope.
+ *
+ * ``` c
+ * {
+ *   GST_OBJECT_AUTO_LOCK (obj, locker);
+ *
+ *   obj->stuff_with_lock();
+ *   if (cond) {
+ *     // No need to unlock
+ *     return;
+ *   }
+ *
+ *   // Unlock before end of scope
+ *   g_clear_pointer (&locker, g_mutex_locker_free);
+ *   obj->stuff_without_lock();
+ * }
+ * ```
+ * Since: 1.24.0
+ */
+#define GST_OBJECT_AUTO_LOCK(obj, var) g_autoptr(GMutexLocker) G_GNUC_UNUSED var = g_mutex_locker_new(GST_OBJECT_GET_LOCK(obj))
+
 /**
  * GST_OBJECT_TRYLOCK:
  * @obj: a #GstObject.

subprojects/gstreamer/gst/gstpad.h

@@ -1249,6 +1249,34 @@ struct _GstPadClass {
  * when buffers or serialized downstream events are pushed on a pad.
  */
 #define GST_PAD_STREAM_LOCK(pad)        g_rec_mutex_lock(GST_PAD_GET_STREAM_LOCK(pad))
+
+/**
+ * GST_PAD_STREAM_AUTO_LOCK
+ * @pad: a #GstPad
+ * @var: a variable name to be declared
+ *
+ * Declare a #GRecMutexLocker variable with g_autoptr() and lock the pad. The
+ * recursive mutex will be unlocked automatically when leaving the scope.
+ *
+ * ``` c
+ * {
+ *   GST_PAD_STREAM_AUTO_LOCK (pad, locker);
+ *
+ *   gst_pad_push_event(pad, event1);
+ *   if (cond) {
+ *     // No need to unlock
+ *     return;
+ *   }
+ *
+ *   // Unlock before end of scope
+ *   g_clear_pointer (&locker, g_rec_mutex_locker_free);
+ *   gst_pad_push_event(pad, event2);
+ * }
+ * ```
+ * Since: 1.24.0
+ */
+#define GST_PAD_STREAM_AUTO_LOCK(pad, var) g_autoptr(GRecMutexLocker) G_GNUC_UNUSED var = g_rec_mutex_locker_new(GST_PAD_GET_STREAM_LOCK(pad))
+
 /**
  * GST_PAD_STREAM_TRYLOCK:
  * @pad: a #GstPad

subprojects/gstreamer/tests/check/gst/gstobject.c

@@ -284,12 +284,18 @@ GST_START_TEST (test_fake_object_name_threaded_right)
 
   /* start looping and set/get name repeatedly */
   for (i = 0; i < 1000; ++i) {
+#ifndef g_autoptr
     GST_OBJECT_LOCK (object);
+#else
+    GST_OBJECT_AUTO_LOCK (object, locker);
+#endif
     g_free (GST_OBJECT_NAME (object));
     GST_OBJECT_NAME (object) = g_strdup ("main");
     THREAD_SWITCH ();
     name = g_strdup (GST_OBJECT_NAME (object));
+#ifndef g_autoptr
     GST_OBJECT_UNLOCK (object);
+#endif
 
     fail_unless (strcmp (name, "main") == 0,
         "Name got changed while lock held during run %d", i);