为线程特定数据创建键

#include <stdlib.h>
#include <pthread.h>
#include <stdio.h>
#include <sched.h>
#include<string.h>
pthread_key_t key;
void destructor(void *data)
//如果创建该键时指定了destructor 函数，则该线程终止时，系统会调用destructor 函数，传进的参数是绑定的值。
 {
       if(data != NULL)
          free(data);
        printf("thread (%u) do free key\n", (unsigned)pthread_self());
}
 void print_key(void)
 {
        char *p;
        p = (char *)pthread_getspecific(key);
        printf("(%u) key_value:%s\n", (unsigned)pthread_self(), p);
 }
  void *thread1(void *arg)
 {
         printf("start thread (%u)\n", (unsigned)pthread_self());
         char * p = malloc(7*sizeof(char));
         memset(p, ‘a‘, 6);
         p[6] = ‘\0‘;
         pthread_setspecific(key, p);//key绑定的值为p
         printf("(%lu)setkey:%s\n", pthread_self(), p);
         print_key();
         printf("thread (%u) end\n", pthread_self());
 }
 void *thread2(void *arg)
 {
         printf("start thread (%u)\n", (unsigned)pthread_self());
         char * p = malloc(7*sizeof(char));
         memset(p, ‘c‘, 6);
         p[6] = ‘\0‘;
         pthread_setspecific(key, p);//key绑定的值为p
         printf("(%lu)setkey:%s\n", pthread_self(), p);
         print_key();
         printf("thread (%u) end\n", pthread_self());
 }
 int main(int argc, char *argv[])
 {
         pthread_t  t1, t2, t3;

         pthread_key_create(&key, destructor);

        pthread_create(&t1, NULL, thread1, NULL);
        pthread_create(&t2, NULL, thread2, NULL);

        pthread_join(t1, NULL);
        pthread_join(t2, NULL);
        printf("main end\n");
      return 0;
 }
//执行结果如下

1.在每个线程结束后系统会执行注册的撤销函数。
2.如果使用pthread_exit()提前终止线程，也会调用撤销函数。