http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50982 --- Comment #23 from David Edelsohn <dje at gcc dot gnu.org> 2011-11-05 06:36:06 UTC --- I suspect that libstdc++ is having problems because pthread_once_t is a struct in AIX. libstdc++ should not be written to assume it is a scalar.