CArena - Race condition on shutting down

[rasmuswz]

A thread starting CArena like:

CArena arena = CArena_new(...);

arena->send(...)
arena->receive(...)

CArena_Destroy(&arena)

there is no guarantee that the actual send-thread in the arena has begun running yet. Thus if it decides to do so after CArena_Destroy it will crash the program :(