Is it good practice to lock a pthread mutex before destroying it? [duplicate]

Question

class AAA
{
    ...
    ~AAA()
    {
        pthread_mutex_lock( &m_mutex );
        pthread_mutex_destroy( &m_mutex );
    }
}

Question> I saw this code somewhere in a project. Is it good practice to do so? Or it is undefined behavior to lock a mutex before destroying it?

Answer 1

It strikes me as utterly terrible practice.

from http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_destroy.html

It shall be safe to destroy an initialized mutex that is unlocked. Attempting to destroy a locked mutex results in undefined behavior.

so this code guarantees undefined behavior and needs to be fixed.

Answer 2

This link says its undefined behavior.

Maybe from where you saw this code, the original coder wanted to destroy the mutex and might have thought that if he/she would be able to lock that mutex, then that means it's unlocked somewhere else by some important thread, and thus he can delete it.

But it's implemented incorrectly.