testf_dso_mutex_unlock
int testf_dso_mutex_unlock(pthread_mutex_t *);
int (*testf_dso_mutex_unlock)(pthread_mutex_t *);
testf_dso_mutex_unlock = dlsym(handle, "testf_dso_mutex_unlock");
ATF_REQUIRE_MSG(testf_dso_mutex_unlock != NULL,
ATF_REQUIRE(testf_dso_mutex_unlock(&mtx) == 0xcafe);