Unix 线程改变创建进程中变量的值（2）

执行环境：Linux ubuntu 4.4.0-31-generic #50-Ubuntu SMP Wed Jul 13 00:07:12 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

1.测试代码： a.c

 #include <fcntl.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <pthread.h>
 #include <string.h>

 pthread_t ntid;

 void * thr_fn(void * arg)
 {
    int * fp = (int *)arg;
    char * str = (char *)arg; 

    printf("I am a thread,receive a string:%s",str);
    printf("Now,I will change it's value.\n");

    strcpy(str,"Changed by a thread!\n");
    return ((void *));
 }

 int main(void)
 {
     int err;
     int fd;
     char parent[] = "I am parent!\n"; 

     fd = open("log.txt",O_CREAT|O_WRONLY);
     if(- == fd)
     {
     printf("Failed to open  file!\n");
     }

     err = pthread_create(&ntid,NULL,thr_fn,parent);
     if(err != )
     {
     printf("can't create thread ,errno = %d\n",err);
     }

     void ** pr;
     err = pthread_join(ntid,pr);
     if(err != )
     {
        printf("error happend when waited a thread!\n");
     }
     printf("In process,the value of the string is %s",parent);
     return ;
 }

2.输出：

I am a thread,receive a string:I am parent!
Now,I will change it's value.
In process,the value of the string is Changed by a thread!

3.创建进程是通过指针传递参数给线程的，线程又是共享创建进程的一些资源的，可以改变进程的变量值。

php 在创建线程的时候，线程对象需要保存进程传递进来参数的值的方式是传值，如果在构造函数中，引用传递进来的参数，会报错误：

Fatal error: Cannot assign by reference to overloaded object。