pthread_attr_getstack
extern int pthread_attr_getstack(const pthread_attr_t *_RESTRICT_KYWD,
if (pthread_attr_getstack(attr, &stackaddr, &stacksize) != 0) {
VERIFY0(pthread_attr_getstack(&selfattr, &selfstk, &selfsz));
VERIFY0(pthread_attr_getstack(&altattr, &altstk, &altsz));
VERIFY0(pthread_attr_getstack(attr, &stk, &stksz));