pthread_key_create析构函数未得到调用 [英] pthread_key_create destructor not getting called

问题描述

根据 pthread_key_create 手册页，我们可以关联一个析构函数在线程关闭时被调用.我的问题是我已注册的析构函数没有被调用.我的代码要点如下.

As per pthread_key_create man page we can associate a destructor to be called at thread shut down. My problem is that the destructor function I have registered is not being called. Gist of my code is as follows.

static pthread_key_t key;
static pthread_once_t tls_init_flag = PTHREAD_ONCE_INIT;

void destructor(void *t) {
  // thread local data structure clean up code here, which is not getting called
}

void create_key() {
  pthread_key_create(&key, destructor);
}

// This will be called from every thread
void set_thread_specific() {

  ts = new ts_stack; // Thread local data structure

  pthread_once(&tls_init_flag, create_key);
  pthread_setspecific(key, ts);
}

有什么想法可以阻止此析构函数被调用?我现在也在使用atexit()在主线程中进行一些清理.是否有可能干扰析构函数的调用?我也尝试将其删除.仍然没有工作.我也不清楚是否应该使用atexit将主线程作为单独的案例处理. (顺便说一句，必须使用atexit，因为我需要在应用程序出口处进行一些特定于应用程序的清理)

Any idea what might prevent this destructor being called? I am also using atexit() at moment to do some cleanup in the main thread. Is there any chance that is interfering with destructor function being called? I tried removing that as well. Still didn't work though. Also I am not clear if I should handle the main thread as a separate case with atexit. (It's a must to use atexit by the way, since I need to do some application specific cleanup at application exit)

推荐答案

这是设计使然.

主线程退出(通过返回或调用exit())，并且不使用pthread_exit(). POSIX文档pthread_exit调用了特定于线程的析构函数.

The main thread exits (by returning or calling exit()), and that doesn't use pthread_exit(). POSIX documents pthread_exit calling the thread-specific destructors.

您可以在main的末尾添加pthread_exit().另外，您可以使用atexit进行销毁.在那种情况下，将特定于线程的值设置为NULL是干净的，因此，在调用pthread_exit的情况下，对该键的销毁不会发生两次.

You could add pthread_exit() at the end of main. Alternatively, you can use atexit to do your destruction. In that case, it would be clean to set the thread-specific value to NULL so in case the pthread_exit was invoked, the destruction wouldn't happen twice for that key.

更新实际上，我已经解决了我的紧迫问题，只需将其添加到我的全局单元测试设置功能中即可.

UPDATE Actually, I've solved my immediate worries by simply adding this to my global unit test setup function:

::atexit([] { ::pthread_exit(0); });

因此，在我的全局夹具类MyConfig中:

So, in context of my global fixture class MyConfig:

struct MyConfig {
    MyConfig()   {
        GOOGLE_PROTOBUF_VERIFY_VERSION;
        ::atexit([] { ::pthread_exit(0); });
    }
    ~MyConfig()  { google::protobuf::ShutdownProtobufLibrary(); }
};

使用了一些参考文献:

• http://www.resolvinghere.com/sof/6357154.shtml
• https://sourceware.org/ml/pthreads-win32/2008/msg00007.html
• http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_key_create.html
• http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_exit.html

• http://www.resolvinghere.com/sof/6357154.shtml
• https://sourceware.org/ml/pthreads-win32/2008/msg00007.html
• http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_key_create.html
• http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_exit.html

PS.当然，c ++ 11 引入了<thread> ，因此您拥有更好，更便携的灵长类动物与之共事.

PS. Of course c++11 introduced <thread> so you have better and more portable primitves to work with.

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