Macos pthread无法加入，出现未知错误

我计划使用pthreads和mach信号量来尝试将并行计算基本上分配给有限数量的cpu，而我无法让测试程序正常工作。现在，我有一些东西，只是通过线程和打印出一些标识符，以便我可以验证它的工作。代码非常简单，除了我在OSX上，所以我必须使用mach信号量而不是POSIX。我的代码在下面

#include <iostream>
#include <pthread.h>
#include <semaphore.h>
#include <errno.h>
#include <mach/semaphore.h>
#include <mach/mach.h>

#define MAX_THREADS 256

semaphore_t free_CPU = 0;

void* t_function(void *arg) {
    int* cur_number;
    cur_number = (int*) arg;
    kern_return_t test = semaphore_wait(free_CPU);
    std::cout << "I am thread # " << *cur_number << ". Kernel return is " << test << std::endl;
    semaphore_signal(free_CPU);
    std::cout << "I am thread # " << *cur_number << ". I just signaled the semaphore." << std::endl;
    pthread_exit(NULL);
}

int main (int argc, char * const argv[]) {
    int num_reps = 10;
    int n_threads = 1;
    if (n_threads < MAX_THREADS) {
        n_threads += 0;
    } else {
        n_threads = MAX_THREADS;
    }
    pthread_t threads[n_threads];

    semaphore_create(mach_task_self(), &free_CPU, SYNC_POLICY_FIFO, 1);

    // Loop over a bunch of things, feeding out to only nthreads threads at a time!
    int i;
    int* numbers = new int[num_reps];
    for (i = 0; i < num_reps; i++) {
        numbers[i] = i;
        std::cout << "Throwing thread " << numbers[i] << std::endl;
        int rc = pthread_create(&threads[i], NULL, &t_function, &numbers[i]);
        if (rc) {
            std::cout << "Failed to throw thread " << i << " Error: " << strerror(errno) << std::endl;
            exit(1);
        }
    }

    std::cout << "Threw all threads" << std::endl;

    // Loop over threads to join
    for (i = 0; i < num_reps; i++) {
        std::cout << "Joining thread " << i << std::endl;
        int rc = pthread_join(threads[i],NULL);
        if (rc) {
            std::cout << "Failed to join thread " << i << ". Error: " << strerror(errno) << std::endl;
            exit(1);
        }
    }

    semaphore_destroy(mach_task_self(), free_CPU);

    delete[] numbers;

    return 0;
}

---

对我来说，看起来一切都很好，只是当它试图连接线程8时，它只是咬了灰尘。我不知道发生了什么事。

你的问题在于：

#define MAX_THREADS 256
:
int n_threads = 1;
if (n_threads < MAX_THREADS) {
    n_threads += 0;
} else {
    n_threads = MAX_THREADS;
}
pthread_t threads[n_threads];

#定义最大线程数256
:
int n_线程=1；
if（n螺纹<最大螺纹）{
n_线程+=0；
}否则{
n_螺纹=最大_螺纹；
}
pthread_t线程[n_线程]；

这将为您提供一个包含一个线程ID的数组。然后您将尝试填充其中的十个线程ID

---

我不完全确定你想用那件事干什么。在我看来，如果您只使用

num_reps

来对数组进行尺寸标注，它会工作得很好（您会得到一个包含十个元素的数组）。

哦，上帝，非常感谢。我想会是这样的@用户1013641：不用叫我上帝，帕克斯会很好的：-）

#define MAX_THREADS 256
:
int n_threads = 1;
if (n_threads < MAX_THREADS) {
    n_threads += 0;
} else {
    n_threads = MAX_THREADS;
}
pthread_t threads[n_threads];