caps: Use G_GNUC_WARN_UNUSED_RESULT for make_writable()

People often call
  gst_caps_make_writable (caps);
instead of
  caps = gst_caps_make_writable (caps);
and cause a bug. Warning about an unused return value helps here.

See https://bugzilla.gnome.org/show_bug.cgi?id=616541#c2 for an example.

diff --git a/gst/gstcaps.h b/gst/gstcaps.h
index e0a2aae..35a1fde 100644 (file)
--- a/gst/gstcaps.h
+++ b/gst/gstcaps.h
@@ -186,7 +186,7 @@ GstCaps *         gst_caps_new_full_valist         (GstStructure  *structure,
 /* reference counting */
 GstCaps *         gst_caps_ref                     (GstCaps       *caps);
 GstCaps *         gst_caps_copy                    (const GstCaps *caps);
-GstCaps *         gst_caps_make_writable           (GstCaps       *caps);
+GstCaps *         gst_caps_make_writable           (GstCaps       *caps) G_GNUC_WARN_UNUSED_RESULT;
 void              gst_caps_unref                   (GstCaps       *caps);
 
 GType             gst_static_caps_get_type         (void);