element: Add sanity check with a critical warning if a pad is requested for a pad...

Various elements are assuming that the pointer matches a pad template
they know about, and also randomly created pad templates might be
missing some important information that is necessary to create a valid
pad.

For example, creating a new pad template for audiomixer's sinkpad
without providing the correct GType would cause audiomixer to create a
GstAggregatorPad. That will then later fail spectacularly because it
assumes that it got a GstAudioAggregatorPad.

Passing a pad template that does not belong to the element class in here
will easily lead to undefined behaviour.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2410>

diff --git a/subprojects/gstreamer/gst/gstelement.c b/subprojects/gstreamer/gst/gstelement.c
index 168bfc2..4394398 100644 (file)
--- a/subprojects/gstreamer/gst/gstelement.c
+++ b/subprojects/gstreamer/gst/gstelement.c
@@ -1165,6 +1165,16 @@ _gst_element_request_pad (GstElement * element, GstPadTemplate * templ,
   }
 #endif
 
+#ifdef GST_ENABLE_EXTRA_CHECKS
+  {
+    if (!g_list_find (oclass->padtemplates, templ)) {
+      /* FIXME 2.0: Change this to g_return_val_if_fail() */
+      g_critical ("Element type %s does not have a pad template %s (%p)",
+          g_type_name (G_OBJECT_TYPE (element)), templ->name_template, templ);
+    }
+  }
+#endif
+
   if (oclass->request_new_pad)
     newpad = (oclass->request_new_pad) (element, templ, name, caps);