id of "main" thread in c++

Question

Is there a way in c++ to get the id of the "main" program thread?

I see that std::this_thread::get_id() gets the id of the currently executing thread but I need the id of the main, original program thread. I don't see any function to get this.

The reason is that I have some non thread safe internal functions that must only be called on the original thread of the application so to be safe I want to do :-

assert(std::this_thread::get_id() == std::main_thread::get_id());

But there of course isn't a function to do that, and I can't see any way to get that information.

Answer 1

You could save it while this_thread is still the original thread:

std::thread::id main_thread_id;

int main() {
    main_thread_id = std::this_thread::get_id(); // gotcha!
    /* go on */
}

Answer 2

This topic seems to be discussed quite a few times here, like in this topic:

• Getting a handle to the process main thread

You can find some solutions, but I'd just think the other way round... When starting the new threads, just supply the id of the main thread to them, and store that in a field in the other threads. If that is not going to change throughout the threads' life, you're good to go, you can reference the "main" thread by those handles.