Question

Are destructors for automatic objects guaranteed to execute if a thread is cancelled asynchronously?

Answer 1

In theory, it SHOULD work fine, but it’s worth testing with your platform.

Cancelling a thread eventually ends up invoking pthread_exit(), which as far as I can tell from googling will invoke destructors. It does this by throwing some kind of ‘guaranteed uncaught’ exception all the way out to the thread wrapper, so all your stack-based objects get destructed in the correct order.

See this page, for example. And this blog post:

When calling pthread_exit() in C++, it
has to destruct all objects that has
been created on stack. This process
called stack unwinding and this is
exactly what happens when you throw an
exception. pthread_exit() utilizes
this feature of C++ to cleanup before
shutting down the thread for good.

To do that pthread_exit() throws some
obscure exception and catches it right
before ditching the thread. This way
it cleans up all objects nicely. On
the other hand, catching … becomes
impossible.