Re: atexit(), dlclose() and more atexit()

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Sun, Jun 28, 2020 at 10:35:27PM +0200, Rhialto wrote:
> I have at hand a program (the current svn trunk of VICE, to be exact)
> which does the following:
> 
> 1. In the original thread, it dlopen()s libavformat.
> 2. libavformat establishes an atexit() handler.
> 3. The main thread starts a new thread, and registers an atexit()
>    handler to clean up that thread.
> 4. main thread exit()s.
> 5. atexit() handler obtains its lock, and calls the handler established in 3.
> 6. said handler tells the new thread to clean up and finish. One of the last
>    things the thread does, is to dlclose() libavformat.
> 7. libavformat's atexit handling gets called, which tries to obtain the
>    same lock that was already obtained, in a different thread, in step
>    5.
> 8. deadlock.
> 
> Who is in the wrong here?

libavformat. Never use atexit() with a handler in a library that can be
closed.

Joerg