c - printf flush at program exit -

I know how the flip of the printf () function works when the program exits Is interested in knowing

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  stdout ?  
 I think it's up to the platform, then take a Linux.  
 It can be implemented using the  GCC  's  __feature__ (dtor)  but then the standard library compiler will depend on me It's not the way that it works.  
 Any explanation or link for the documentation is appreciated. Thank you.   
 
 
 C will run Runtime  atexit ()  to flush the handlers < / P> 
 See it.    Standard buffers when  exit ()