线程为什么gcc编译通过， g++编译失败

 

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
void thread(void)
{
    int i;
    for(i=0;i<3;i++)
     printf("This is a pthread.\n");
}

int main(void)
{
    pthread_t id;
    int i,ret;
    ret=pthread_create(&id,NULL,(void *) thread,NULL);
    if (ret != 0) {
        printf ("Create pthread error!\n");
        exit (1);
    }
    for(i=0;i<3;i++)
     printf("This is the main process.\n");
    pthread_join(id,NULL);
    return (0);
}

 

//gcc编译通过
This is the main process.
This is the main process.
This is the main process.
This is a pthread.
This is a pthread.
This is a pthread.
//g++编译失败如下
example.c: In function ‘int main()’:
example.c:13: error: invalid conversion from ‘void*’ to ‘void* (*)(void*)’
example.c:13: error:   initializing argument 3 of ‘int pthread_create(pthread_t*, const pthread_attr_t*, void* (*)(void*), void*)’

要使g++编译通过，方法如下：

C++禁止将void指针随意赋值给其他指针。
因此你在把void thread(void)函数的入口转换为void*，然后当作参数调用pthread_create时就出现错误，因为pthread_create的参数里应该是指向形如void* fun(void*)函数的一个指针。
可以修改void thread(void)为void* thread(void*)，然后去掉调用时的(void*)强制转换，错误消除。