// int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine) (void *), void *arg);

typedef struct {
    pthread_t *thread;
    pthread_attr_t *attr;
    void *(*start_routine) (void *argx);
    void *arg;
    int retval;
} ptc_arg_t;

int the_return_value;

void *func(void *arg) {
    ptc_arg_t *real_args = (ptc_arg_t *)arg;
    int result = pthread_create(real_args->thread, real_args->attr,
        real_args->start_routine, real_args->arg);
    // option
    void *retval = (void *)&result;
    return retval; // return pointer to the sack -- bad
    // option
    int *tmp = malloc(sizeof(int)); // slow
    *tmp = result;
    return (void *)tmp; // user has to free -- can always work & least confusing
    // option
    the_return_value = result; // not thread-safe: all threads share one global
    return NULL;
    // option
    *arg = result; // type error
    return NULL;
    // option
    real_args->retval = result; // can work
    return NULL;
    // option
    return (void *)result; // cast 32-bit int as a 64-bit int
}