for (i = 0; i < virNetworkDriverTabCount; i++) { if ((virDriverTab[i]->probe != NULL) && ((latest = virDriverTab[i]->probe()) != NULL)) { probes++; ..... } } We use array virDriverTab, but cicle is to virNetworkDriverTabCount which count number of virNetworkDriverTab drivers. I think virDriverTabCount should be used. Index: libvirt.c =================================================================== RCS file: /data/cvs/libvirt/src/libvirt.c,v retrieving revision 1.147 diff -u -p -r1.147 libvirt.c --- libvirt.c 26 Jun 2008 09:37:51 -0000 1.147 +++ libvirt.c 10 Jul 2008 14:48:44 -0000 @@ -699,7 +699,7 @@ do_open (const char *name, const char *use = NULL; const char *latest; int probes = 0; - for (i = 0; i < virNetworkDriverTabCount; i++) { + for (i = 0; i < virDriverTabCount; i++) { if ((virDriverTab[i]->probe != NULL) && ((latest = virDriverTab[i]->probe()) != NULL)) { probes++;