__thread 和 __typeof__关键字

__thread 和 __typeof__关键字  

2012-04-16 17:22:30|  分类： C program|字号 订阅

__thread:在多线程变成中，使用于global变量，使每个线程都私有一份。

static __thread int count;

void *function1(void *argc)

{

printf("porgran pid:%u, the function1 pthread id is %lu, count:%d\n",getpid(), pthread_self(), count);

count = 10;

printf("porgran pid:%u, last the function1 pthread id is %lu, count:%d\n",getpid(), pthread_self(), count);

return 0;

}

void *function2(void *argc)

{

printf("porgran pid:%u, the function2 pthread id is %lu, count:%d\n", getpid(), pthread_self(), count);

sleep(2);

count = 100;

printf("porgran pid:%u, last the function2 pthread id is %lu, count:%d\n", getpid(), pthread_self(), count);

return 0;

}

int main()

{

pthread_t  thread_id[2];

int ret;

pthread_t mian_thread_id;

mian_thread_id = pthread_self();

count = 2;

printf("porgran pid:%u, mian_thread_id:%lu, count:%d\n", getpid(), mian_thread_id, count);

ret = pthread_create(thread_id, NULL, function1, NULL);

assert(ret == 0);

ret = pthread_create(thread_id + 1, NULL, function2, NULL);

assert(ret == 0);

ret = pthread_join(thread_id[0], NULL);

assert(ret == 0);

ret = pthread_join(thread_id[1], NULL);

assert(ret == 0);

count = 1000;

printf("porgran pid:%u, last mian_thread_id:%lu, count:%d\n", getpid(), mian_thread_id, count);

return 0;

}

__typeof__(var) 是gcc对C语言的一个扩展保留字，用于声明变量类型,var可以是数据类型（int， char*..),也可以是变量表达式。

define DEFINE_MY_TYPE(type, name) __thread __typeof__(type) my_var_##name

DEFINE_MY_TYPE(int, one); //It   is   equivalent   to  '__thread int  my_var_'; which is a thread variable.

int main()

{

__typeof__(int *) x; //It   is   equivalent   to  'int  *x';

__typeof__(int) a;//It   is   equivalent   to  'int  a';

__typeof__(*x)  y;//It   is   equivalent   to  'int y';

__typeof__(&a) b;//It   is   equivalent   to  'int  b';

__typeof__(__typeof__(int *)[4])   z; //It   is   equivalent   to  'int  *z[4]';

y = *x;

b = &a;

z[0] = x;

z[1] = &a;

return 0;

}