PROP_STACK_INTERN_ELEMS
if (stack->used_intern_elems == PROP_STACK_INTERN_ELEMS) {
_PROP_ASSERT(stack->used_intern_elems < PROP_STACK_INTERN_ELEMS);
_PROP_ASSERT(stack->used_intern_elems == PROP_STACK_INTERN_ELEMS);
struct _prop_stack_intern_elem intern_elems[PROP_STACK_INTERN_ELEMS];