Consider a tail recursive factorial implementation in C:
#include <stdio.h>
unsigned long long factorial(unsigned long long fact_so_far, unsigned long long count, unsigned long long max_count){
if (max_count==0 || max_count==1 || count >= max_count)
return fact_so_far;
else
{
printf("%llu %p \n", count, &factorial);
return factorial(fact_so_far * count, ++count, max_count);
}
}
int main(int argc, char **argv)
{
unsigned long long n;
scanf("%llu", &n);
printf("\n Factorial %llu \n",factorial(1,0,n));
return 0;
}
I place a breakpoint in 'factorial' and I run the above under 'gdb'. The breakpoint is never hit.
Assuming that its tail call optimised (I have compiled it using gcc -O2), it should hit the breakpoint, atleast once, IIRC.
EDIT: I get the final result without hitting any breakpoint. For eg,
(gdb) b factorial
Breakpoint 1 at 0x8048429: file factorial-tail.c, line 3.
(gdb) run
Starting program: /home/amit/quest/codes/factorial-tail
5
0 0x8048420
1 0x8048420
2 0x8048420
3 0x8048420
4 0x8048420
Factorial 120
Program exited normally.
(gdb)
Where am I going wrong?
