正确的线程传参：

 
#include <pthread.h>
#include <errno.h>
#include <stdio.h>
 
 
void* say_hello(void* fd)
{
    //对传入的参数进行强制类型转换，由无类型指针变为整形数指针，然后再读取；
    int connectfd =*((int *)fd);
    printf("thread connectfd:%d\n",connectfd);
    pthread_exit(NULL);

}
 
int main()
{
    pthread_t thread_recv;
    
      int i = -3;
    int ret = pthread_create(&thread_recv, NULL, say_hello, (void *)&i);//传入的时候必须强制转换为void* 类型，即无类型指针
    printf("current pthread id = %d\n",thread_recv);
    if (ret != 0)
    {
       printf("pthread_create error: error_code=%d",ret);
    }
    ret = pthread_join(thread_recv,NULL);
    if(ret) {
        perror ("pthread_join join error:");
        return ret;
    }
    while(1);
    
}

 

优化代码这样写时，线程的传参是错误的，不知道问题出在哪了。

 
#include <pthread.h>
#include <errno.h>
#include <stdio.h>
 
pthread_t thread_recv;
 
void* say_hello(void* fd)
{
    //对传入的参数进行强制类型转换，由无类型指针变为整形数指针，然后再读取；
    int connectfd =*((int *)fd);
    printf("thread connectfd:%d\n",connectfd);
    pthread_exit(NULL);

}
 
void thread_init(int val)
{
    int ret = pthread_create(&thread_recv, NULL, say_hello, (void *)&val);//传入的时候必须强制转换为void* 类型，即无类型指针
    printf("current pthread id = %d\n",thread_recv);
    if (ret != 0)
    {
       printf("pthread_create error: error_code=%d",ret);
    }
}
int main()
{
  
    int ret = -1;
      int i = -3;
    thread_init(i);
    ret = pthread_join(thread_recv,NULL);
    if(ret) {
        perror ("pthread_join join error:");
        return ret;
    }
    while(1);
    
}