c - printf flush at program exit

Question

I'm interested in knowing how the printf() function's flush works when the program exits.

Let's take the following code:

int main(int ac, char **av)
{
    printf("Hi");
    return 0;
}

In this case, how does printf() manage to flush its buffer to stdout?

I guess it's platform dependent, so let's take Linux.

It could be implemented using gcc's __attribute__((dtor)) but then the standard library would be compiler dependent. I assume this is not the way it works.

Any explanations or links to documentation is appreciated. Thank you.

Answer 1

The C runtime will register atexit() handlers to flush standard buffers when exit() is called.

See this explanation.