Hey everyone, my first post here, so lets see if I do this right.
So I have this assignment that links a fibonacci.c, fib.h, and fib.s file. The assignment is supposed to be done by compiling all of the files, then running ./fibonacci <n> where <n> is the n'th term that should be printed out of the fibonacci sequence. Here's what I have so far:
my fibonacci.c:
#include <stdio.h>
#include "fib.h"
int main(int argc, char*argv[]){
int x;
x=atoi(argv[1]);
printf("%d\n",fib(x));
return 0;
}fib.h, which was provided for the assignment:
#ifndef _FIB_H_
#define _FIB_H_
extern int fib(int n);
#endifand my fib.s, where the work should be done:
.file "fib.c"
.text
.globl fib
.type fib, @function
fib:
pushl %ebp
movl %esp, %ebp
subl $32, %esp
movl $0, -20(%ebp)
movl $0, -4(%ebp)
movl $1, -8(%ebp)
movl 20(%esp), %esi
jmp .L2
.L3:
movl -4(%ebp), %eax
movl %eax, -12(%ebp)
movl -8(%ebp), %eax
addl %eax, -4(%ebp)
movl -12(%ebp), %eax
movl %eax, -8(%ebp)
addl $1, -20(%ebp)
.L2:
cmpl %esi, -20(%ebp) #-20 is my i counter
jle .L3
movl -12(%ebp), %eax
leave
ret
.size fib, .-fib
.ident "GCC: (Ubuntu 4.4.3-4ubuntu5) 4.4.3"
.section .note.GNU-stack,"",@progbitsAll of this works fine, (oh, this is using GNU Assembler, GAS), and compiles on Linux..
My question is, since I'm running this through the C file, i know that argv[1] is my N term, and i send that as an int to the fibs.s file.. but where does it get stored in fib.s? Basically if I compile it:
-> gcc fibonacci.c fib.s -o fibonacci
-> ./fibonacci 7
..should print out 13
...where in the Assembler is that 7 stored? I want to put that number in my "%esi" and so my loop will work that many times. I thought it would be stored in %ebp, but it's apparently not?