http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60662
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- -lpthread (or more correctly, -pthread) should cause the executable to link to libpthread.so for pthread_once, but for some reason on your system is preferring the weak pthread_once symbol found in libc.so and so your executable is not linked to libpthread.so I do not think that is a GCC problem.