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c - 编译时出错

转载 作者:行者123 更新时间:2023-12-02 10:41:43 24 4
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我正在尝试编译此代码:

/* Includes */
#include <unistd.h> /* Symbolic Constants */
#include <sys/types.h> /* Primitive System Data Types */
#include <errno.h> /* Errors */
#include <stdio.h> /* Input/Output */
#include <stdlib.h> /* General Utilities */
#include <pthread.h> /* POSIX Threads */
#include <string.h> /* String handling */
#include <semaphore.h> /* Semaphore */

/* prototype for thread routine */
void handler ( void *ptr );

/* global vars */
/* semaphores are declared global so they can be accessed
in main() and in thread routine,
here, the semaphore is used as a mutex */
sem_t mutex;
int counter; /* shared variable */

int main()
{
int i[2];
pthread_t thread_a;
pthread_t thread_b;

i[0] = 0; /* argument to threads */
i[1] = 1;

sem_init(&mutex, 0, 1); /* initialize mutex to 1 - binary semaphore */
/* second param = 0 - semaphore is local */

/* Note: you can check if thread has been successfully created by checking return value of
pthread_create */
pthread_create (&thread_a, NULL, (void *) &handler, (void *) &i[0]);
pthread_create (&thread_b, NULL, (void *) &handler, (void *) &i[1]);

pthread_join(thread_a, NULL);
pthread_join(thread_b, NULL);

sem_destroy(&mutex); /* destroy semaphore */

/* exit */
exit(0);
} /* main() */

void handler ( void *ptr )
{
int x;
x = *((int *) ptr);
printf("Thread %d: Waiting to enter critical region...\n", x);
sem_wait(&mutex); /* down semaphore */
/* START CRITICAL REGION */
printf("Thread %d: Now in critical region...\n", x);
printf("Thread %d: Counter Value: %d\n", x, counter);
printf("Thread %d: Incrementing Counter...\n", x);
counter++;
printf("Thread %d: New Counter Value: %d\n", x, counter);
printf("Thread %d: Exiting critical region...\n", x);
/* END CRITICAL REGION */
sem_post(&mutex); /* up semaphore */

pthread_exit(0); /* exit thread */
}

但我收到此错误:
sem-ex.c: In function ‘int main()’:
sem-ex.c:35: error: invalid conversion from ‘void*’ to ‘void* (*)(void*)’
sem-ex.c:35: error: initializing argument 3 of ‘int pthread_create(_opaque_pthread_t**, const pthread_attr_t*, void* (*)(void*), void*)’
sem-ex.c:36: error: invalid conversion from ‘void*’ to ‘void* (*)(void*)’
sem-ex.c:36: error: initializing argument 3 of ‘int pthread_create(_opaque_pthread_t**, const pthread_attr_t*, void* (*)(void*), void*)’

我错过了什么/做错了什么?谢谢。

最佳答案

你不能投你的地址 handle函数到 void *在将其传递给 pthread_create 之前.只需按原样传递即可。

pthread_create (&thread_a, NULL, &handler, (void *) &i[0]);
pthread_create (&thread_b, NULL, &handler, (void *) &i[1]);

另外,更改您的 handler根据下面的 nos 评论,函数的签名。

关于c - 编译时出错,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6193426/

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