c macro pair

成对使用的macro, 不过也有机会用错, 死都不知道怎么死的, 这宏...

#define pthread_cleanup_push(func, val) 
   { 
         struct __darwin_pthread_handler_rec __handler; 
         pthread_t __self = pthread_self(); 
         __handler.__routine = func; 
         __handler.__arg = val; 
         __handler.__next = __self->__cleanup_stack; 
         __self->__cleanup_stack = &__handler;

#define pthread_cleanup_pop(execute) 
         /* Note: 'handler' must be in this same lexical context! */ 
         __self->__cleanup_stack = __handler.__next; 
         if (execute) (__handler.__routine)(__handler.__arg); 
   }