def_thrattr
extern const thrattr_t *def_thrattr(void);
old_attr ? old_attr->__pthread_attrp : def_thrattr();
const thrattr_t *ap1 = attr1 ? attr1->__pthread_attrp : def_thrattr();
const thrattr_t *ap2 = attr2 ? attr2->__pthread_attrp : def_thrattr();
*ap = *def_thrattr();
const thrattr_t *ap = attr? attr->__pthread_attrp : def_thrattr();