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Comment by leeter | Hacker News Reader

I'm reminded of Raymond Chen's many many blogs[1][2][3](there are a lot more) on why TerminateThread is a bad idea. Not surprised at all the same is true elsewhere. I will say in my own code this is why I tend to prefer cancellable system calls that are alertable. That way the thread can wake up, check if it needs to die and then GTFO.

[1] https://devblogs.microsoft.com/oldnewthing/20150814-00/?p=91...

[2] https://devblogs.microsoft.com/oldnewthing/20191101-00/?p=10...

[3] https://devblogs.microsoft.com/oldnewthing/20140808-00/?p=29...

there are a lot more, I'm not linking them all here.

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One of my more annoying gotchas on Windows is that despite this advice being very reasonable sounding, the runtime itself (I believe it actually happens in the kernel) essentially calls TerminateThread on all child threads before running global destructors and atexit hooks. Good luck following this advice when the kernel actively fights you when it come time to shutdown

So there is a reason that in the C++ spec if a std::thread is still joinable when the destructor is called it calls std::terminate[1]. That reason being exactly this case. If the house is being torn down it's not safe to try to save the curtains[2]. Just let the house get torn down as quickly as possible. If you wanted to save the curtains (e.g. do things on the threads before they exit) you need to do it before the end of main and thus global destructors start getting called.

[1] https://en.cppreference.com/w/cpp/thread/thread/~thread.html

[2] https://devblogs.microsoft.com/oldnewthing/20120105-00/?p=86...

Global destructors and atexit are called by the C/C++ runtime, Windows has nothing to do with that. The C and C++ specs require that returning from main() has the same effect of ending the process as exit() does, meaning they can’t allow any still-running threads to continue running. Given these constraints, would you prefer the threads to keep running until after global destructors and atexit have run? That would be at least as likely to wreak havoc. No, in C/C++, you need to make sure that other threads are not running anymore before returning from main().

When you return from main(), there shouldn't be any child threads running in the first place. Join your threads and you will be fine.

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