Yes, my use case is a application running in a terminal that I want to end with Ctrl+C. This is currently broken. As well as applications with segfaults (or other signals). They go on forever.

Ok, then this should be re-added for non-windows systems only as there we're sure that the process is being terminated once we reach that point in the execution.

Really? If the termination handler doesn't abort, the process won't continue to run? That sounds odd to me ...
I guess what we rather want to have is to move the abort into the if statement to not cause the python application to abort in that case?

On Windows, if the termination handler returns TRUE, then no other handler functions are called and the system terminates the process (see: https://docs.microsoft.com/en-us/windows/console/handlerroutine).

Thanks @hkaiser for the explanation. I pushed a new version of the changes removing std::abort for windows.