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