As reported in https://bugs.gentoo.org/show_bug.cgi?id=300961 : # gcc foo.c -lpython2.6 /usr/lib/gcc/i686-gentoo-freebsd7.2/4.4.2/../../../libpython2.6.so: undefined reference to `pthread_create' collect2: ld returned 1 exit status libpython2.6.so doesn't get linked with -pthread; I'll attach a patch fixing this, the configure script does its magic but doesn't reuse that magic for setting LDSHARED.