This chapter is about functions that call themselves. Consider the
program below:
#include <stdio.h>
void black_hole()
{
black_hole();
}
/* To shorten example, not using argp */
int main ()
{
black_hole();
return 0;
}
The main function calls the black_hole function, which
calls itself, which calls itself, which calls... Once the control
flow enters black_hole, it will never exit. This kind of
function is called a recursive function, and a function's act of
calling itself is called recursion.