pthread_cleanup_push导致语法错误

Question

我尝试在我的代码中添加一个部分,它可以在取消的情况下解锁互斥锁.这可能会发生并导致死锁.因此我尝试添加,pthread_cleanup_push(cleanup_unlock_mutex, &mutex_ftdi);但这行导致语法错误从我添加它直到代码文件的末尾的行.如果我评论代码行,程序将编译没有任何错误.我做错了什么？

void cleanup_unlock_mutex(void *p){
    pthread_mutex_unlock(p);
}

....... }else{
                for(unsigned count=0; count <= number_of_requests; count++){
                    pthread_cleanup_push(cleanup_unlock_mutex, &mutex_ftdi);
                    pthread_mutex_lock(&mutex_ftdi);
                    process_requests(count, numberofthread);
                    pthread_mutex_unlock(&mutex_ftdi);
                }
            } // compiler error: error: expected ‘while’ before ‘}’ token
..........

文件中的所有其他函数都会收到警告:ISO C禁止嵌套函数[-pedantic].

Answer 1

您必须呼叫pthread_cleanup_push()并pthread_cleanup_pop()配对,并且您的代码段没有pthread_cleanup_pop()呼叫.

http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_cleanup_pop.html上的文档解释了原因:

这些功能可以实现为宏.申请书应确保它们出现的语句,并在相同的词法范围内对(也就是pthread_cleanup_push()宏可能被认为扩大到令牌列表的第一个符号是'{'具有 pthread_cleanup_pop()扩展到令牌列表,它的最后一个令牌对应'}') .

为了使这个具体,一个可能的实现,取自glibc nptl/sysdeps/pthread/pthread.h:

/* Install a cleanup handler: ROUTINE will be called with arguments ARG
   when the thread is canceled or calls pthread_exit.  ROUTINE will also
   be called with arguments ARG when the matching pthread_cleanup_pop
   is executed with non-zero EXECUTE argument.

   pthread_cleanup_push and pthread_cleanup_pop are macros and must always
   be used in matching pairs at the same nesting level of braces.  */
#  define pthread_cleanup_push(routine, arg) \
  do {                                        \
    __pthread_cleanup_class __clframe (routine, arg)

/* Remove a cleanup handler installed by the matching pthread_cleanup_push.
   If EXECUTE is non-zero, the handler function is called. */
#  define pthread_cleanup_pop(execute) \
    __clframe.__setdoit (execute);                        \
  } while (0)