Вот пример, взятый из библиотеки потоков пользовательского уровня GnuPth (pth_lib.c), которая показывает реализацию функций exit и join соответственно. Я упростил код, чтобы выделить обработку возвращаемого значения.
void pth_exit(void *value)
{
pth_debug2("pth_exit: marking thread \"%s\" as dead", pth_current->name);
/* the main thread is special, because its termination
would terminate the whole process, so we have to delay
its termination until it is really the last thread */
/* execute cleanups */
/*
* Now mark the current thread as dead, explicitly switch into the
* scheduler and let it reap the current thread structure; we can't
* free it here, or we'd be running on a stack which malloc() regards
* as free memory, which would be a somewhat perilous situation.
*/
pth_current->join_arg = value;
pth_current->state = PTH_STATE_DEAD;
pth_debug2("pth_exit: switching from thread \"%s\" to scheduler", pth_current->name);
//return (for ever) to the scheduler
}
и соответствующий pth_join:
/* waits for the termination of the specified thread */
int pth_join(pth_t tid, void **value)
{
//Validate thread situation.
//wait until thread death
//save returned value for the caller
if (value != NULL)
*value = tid->join_arg;
//remove thread from the thread queue
//free its memory space
return TRUE;
}