https://bugs.gentoo.org/869380
https://github.com/dajobe/raptor/commit/567d4d1ab639d924e8d5af459476f331b9af0ce5

From: Dave Beckett <dave@dajobe.org>
Date: Tue, 4 Nov 2014 15:25:20 -0800
Subject: [PATCH] Fix error returns in new world methods

(raptor_world_get_parser_factory,
raptor_world_get_serializers_count): Fix return value in assertions
--- a/src/raptor_parse.c
+++ b/src/raptor_parse.c
@@ -252,12 +252,12 @@ raptor_world_get_parser_factory(raptor_world *world, const char *name)
  *
  * Get number of parsers
  *
- * Return value: number of parsers
+ * Return value: number of parsers or <0 on failure
  **/
 int
 raptor_world_get_parsers_count(raptor_world* world)
 {
-  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, NULL);
+  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, -1);
 
   raptor_world_open(world);
 
--- a/src/raptor_serialize.c
+++ b/src/raptor_serialize.c
@@ -235,12 +235,12 @@ raptor_get_serializer_factory(raptor_world* world, const char *name)
  *
  * Get number of serializers
  *
- * Return value: number of serializers
+ * Return value: number of serializers or <0 on failure
  **/
 int
 raptor_world_get_serializers_count(raptor_world* world)
 {
-  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, NULL);
+  RAPTOR_ASSERT_OBJECT_POINTER_RETURN_VALUE(world, raptor_world, -1);
 
   raptor_world_open(world);