从不兼容的指针类型 [-Wincompatible-pointer-types] 获取传递“pthread_create”参数 3 的警告

Question

我正在运行下面的代码，它工作正常，但它仍然给出了一些我不明白的警告。 有人可以向我解释一下吗？ 谢谢

#include <stdio.h>
#include <pthread.h>

void* the_thread_func(double data_for_thread[]) {
  /* Do something here? */

        for(int i=0;i<3;i++){
    double sum = sum + data_for_thread[i];
    printf("The sum done by the_thread_func()  is = %f\n",sum);
   }

  return NULL;
}

int main() {
  printf("This is the main() function starting.\n");

  double data_for_thread[3];
  data_for_thread[0] = 5.7;
  data_for_thread[1] = 9.2;
  data_for_thread[2] = 1.6;

  /* Start thread. */
  pthread_t thread;
  printf("the main() function now calling pthread_create().\n");
  pthread_create(&thread, NULL, the_thread_func, data_for_thread);

  printf("This is the main() function after pthread_create()\n");

  /* Do something here? */

   for(int i=0;i<3;i++){
   double sum = sum + data_for_thread[i];
    printf("The sum done by main() is = %f\n",sum);
   }

  /* Wait for thread to finish. */
  printf("the main() function now calling pthread_join().\n");
  pthread_join(thread, NULL);

  return 0;
}

警告：从不兼容的指针类型 [-Wincompatible-pointer-types] pthread_create(&thread, NULL, the_thread_func, data_for_thread); ^~~~~~~~~~~~~~~ 在thread_data.c:2:0: /usr/include/pthread.h:234:12: 注意：预期'void * (*)(void *)' but argument is of type 'void * (*)(double *)' extern int pthread_create (pthread_t *__restrict __newthread,

Answer 1

根据手册pthread_create需要给出一个具有此签名的 function：

void* (*start_routine)(void*)

但是您传递给它的 function 在这里接受double* ：

void* the_thread_func(double data_for_thread[]) // decays to double*

我认为您需要更改签名并将void*投射到 function 中，如下所示：

// accept void*
void* the_thread_func(void* vp) {
  /* Do something here? */

    double* data_for_thread = reinterpret_cast<double*>(vp); // cast here

    for(int i=0;i<3;i++){
        double sum = sum + data_for_thread[i];
        printf("The sum done by the_thread_func()  is = %f\n",sum);
    }

    return nullptr;
}