meta: handle multiple implementation registration

First check that we can actually register the implementation before
making a GstMetaInfo. If we can't register we would otherwise end
up with an undefined type and an invalid GstMetaInfo.

It's possible that type registration fails because another metadata
with the same implementation name was already registered.

diff --git a/gst/gstmeta.c b/gst/gstmeta.c
index 2ac6964..2ad0041 100644 (file)
--- a/gst/gstmeta.c
+++ b/gst/gstmeta.c
@@ -142,14 +142,20 @@ gst_meta_register (GType api, const gchar * impl, gsize size,
     GstMetaTransformFunction transform_func)
 {
   GstMetaInfo *info;
+  GType type;
 
   g_return_val_if_fail (api != 0, NULL);
   g_return_val_if_fail (impl != NULL, NULL);
   g_return_val_if_fail (size != 0, NULL);
 
+  /* first try to register the implementation name. It's possible
+   * that this fails because it was already registered. */
+  type = g_pointer_type_register_static (impl);
+  g_return_val_if_fail (type != 0, NULL);
+
   info = g_slice_new (GstMetaInfo);
   info->api = api;
-  info->type = g_pointer_type_register_static (impl);
+  info->type = type;
   info->size = size;
   info->init_func = init_func;
   info->free_func = free_func;