Bug#613411: More info

[Dave Beckett]

On 2/15/11 7:21 AM, Adrian Knoth wrote:
> Hi!
> 
> I've built a debug version of librdf and found the following code:
> 
> librdf_parser_raptor_constructor (world=0x877e5a0) at
> rdf_parser_raptor.c:1328
> 1328        syntax_name = desc->names[0];
> (gdb) bt
> #0  librdf_parser_raptor_constructor (world=0x877e5a0)
>     at rdf_parser_raptor.c:1328
> #1  0xb65b27bd in librdf_init_parser (world=0x877e5a0) at rdf_parser.c:55
> #2  0xb65a3ca5 in librdf_world_open (world=0x877e5a0) at rdf_init.c:303
> #3  0xb64e739c in slv2_world_new () from /usr/lib/libslv2.so.9
> #4  0xb7f6b3a9 in ARDOUR::LV2World::LV2World() ()
>    from /usr/lib/ardour2/libardour.so
> #5  0xb7eaefd4 in ARDOUR::PluginManager::PluginManager() ()
>    from /usr/lib/ardour2/libardour.so
> #6  0xb7e5a184 in ARDOUR::init(bool, bool) ()
>    from /usr/lib/ardour2/libardour.so
> #7  0x08165255 in ARDOUR_UI::ARDOUR_UI(int*, char***) ()
> #8  0x08392e5b in main ()
> (gdb) frame 0
> #0  librdf_parser_raptor_constructor (world=0x877e5a0)
>     at rdf_parser_raptor.c:1328
> 1328        syntax_name = desc->names[0];
> (gdb) list
> 1323        if(!desc) {
> 1324          /* reached the end of the parsers, now register the
> default one */
> 1325          i = 0;
> 1326          desc =
> raptor_world_get_parser_description(world->raptor_world_ptr, i);
> 1327        }
> 1328        syntax_name = desc->names[0];
> 1329        syntax_label = desc->label;
> 1330        if(desc->mime_types)
> 1331          mime_type = desc->mime_types[0].mime_type;
> 1332        if(desc->uri_strings)
> (gdb) p desc
> $1 = (const raptor_syntax_description *) 0x0
> 
> 
> This code has been added after librdf0-1.0.10 for librdf-1.0.11.
> Obviously, description is NULL, and dereferencing it causes the
> segfault.
> 
> I wonder if raptor_world_get_parser_description should have returned
> something different. I cannot judge if it's something big or if a simple
> NULL pointer check  in librdf_parser_raptor_constructor would be enough,
> maybe also using the old code from 1.0.10 in case of desc==NULL.

The desc should never be NULL since it's running through a list from raptor,
and the final one is to get the default parser.  The only way this can
happen is if raptor wasn't initialised properly, which is my guess here.  I
suspect ardour is linking to raptor1 and raptor2, and thus crashing.


> Dajobe, I guess we could use your input here. ;)
> 
> JFTR, this is the initialization code in libslv2:
> 
> SLV2World
> slv2_world_new()
> {
> 	SLV2World world = (SLV2World)malloc(sizeof(struct _SLV2World));
> 
> 	world->world = librdf_new_world();
> 	if (!world->world) {
> 		free(world);
> 		return NULL;
> 	}
> 
> 	world->local_world = true;
> 
> 	librdf_world_open(world->world);
> 
> 	return slv2_world_new_internal(world);
> }
> 
> 
> Cheers
>