Recursion without recursion... or is it?

This works on 32-bit x86 Linux with gcc as long as you don't enable optimization.


#include <stdio.h>
#include <stdlib.h>

static void factorial(int in, int *out) {
        *(&in-1)-=5-5*(1/in);
        *out*=in--;
}

int main(int argc, char **argv) {
        int result=1;
        int number=0;

        if(argc!=2) {
                exit(1);
        }

        number=atoi(argv[1]);

        if(number<1) {
                exit(2);
        }

        factorial(number, &result);

        printf("%d! = %d\n", number, result);

        return 0;
}

$ ./factorial 3
3! = 6
$ ./factorial 5
5! = 120

./factorial 100
Doesn't work anymore.

that will break on gcc 4+

forgot your [code]

<>

care to explain this black magic, OP?

>>6 SEPPLES IS NOT MAGIC, FAGGOT

Quit FUCKING HAVING ANAL SEX WITH POINTERS.

SEX OFFENDERS NEED ACCESS TO CHILDREN TOO!

Your code exploited a buffer overflow in my compiler which caused the instruction pointer to jump to a low-level API that opens the CD-ROM drive. I had a CD burning there, so it flew out of the drive and cut my cat's throat. Now my only friend is dead. Thanks a lot.

>>10
You think you're doing bad? I don't have any friends in the first place! ;_;

>>10
Why don't you have a backup cat?

>>12
My backup cat is in cold storage

>>13
My other cat is a tac

cat and cdr?

>>14,15
FAIL!
cdt

>>16
hey vipman how you feeling about the reddit niggaz?

>>16 is correct.

>>17
I love them and so should you, fucking anus h4x0r.

>>16
Cuddet?

>>19
You are not a true VIPPER.
The redditers are imageboard scum and should be treated like that.

As for you >>19san, you do not deserve the tag of VIPPER, i hope you will burn in hell.

>>21
I have infiltrated your base and I will destroy it from the inside.

VIPPER is a fag

Very nice! :-)

AFAICS the first statement in factorial() warps the return address pointer on the stack 5 bytes back (unless 'in' is 1), so after returning from factorial, the PC is back on the statement of jumping to the subroutine factorial() again.  So, effectively Anonymous loops by doing this.

But I've never seen this done in C before, so thank you for the inspiring idea!

JAVA