The select() was not interrupted in a traditional sense. It looks like a special windows API was used (QueueUserAPC) which allows a callback to be called in user space while blocked in certain kernel calls. My guess is that when used normally, the callback returns and control goes back to select() being blocked, but in this case an exception was thrown which unrolled the stack and left the select() call holding onto an invalid stack address. Jumping out of a syscall using an exception like this will probably cause all kinds of problems and my guess this is completely unsupported.

https://docs.microsoft.com/en-us/windows/win32/api/processth...