C to Assembly code - what does it mean
- by Smith
I'm trying to figure out exactly what is going on with the following assembly code. Can someone go down line by line and explain what is happening? I input what I think is happening (see comments) but need clarification.
.file "testcalc.c"
.section .rodata.str1.1,"aMS",@progbits,1
.LC0:
.string "x=%d, y=%d, z=%d, result=%d\n"
.text
.globl main
.type main, @function
main:
leal 4(%esp), %ecx // establish stack frame
andl $-16, %esp // decrement %esp by 16, align stack
pushl -4(%ecx) // push original stack pointer
pushl %ebp // save base pointer
movl %esp, %ebp // establish stack frame
pushl %ecx // save to ecx
subl $36, %esp // alloc 36 bytes for local vars
movl $11, 8(%esp) // store 11 in z
movl $6, 4(%esp) // store 6 in y
movl $2, (%esp) // store 2 in x
call calc // function call to calc
movl %eax, 20(%esp) // %esp + 20 into %eax
movl $11, 16(%esp) // WHAT
movl $6, 12(%esp) // WHAT
movl $2, 8(%esp) // WHAT
movl $.LC0, 4(%esp) // WHAT?!?!
movl $1, (%esp) // move result into address of %esp
call __printf_chk // call printf function
addl $36, %esp // WHAT?
popl %ecx
popl %ebp
leal -4(%ecx), %esp
ret
.size main, .-main
.ident "GCC: (Ubuntu 4.3.3-5ubuntu4) 4.3.3"
.section .note.GNU-stack,"",@progbits
Original code:
#include <stdio.h>
int calc(int x, int y, int z);
int main()
{
int x = 2;
int y = 6;
int z = 11;
int result;
result = calc(x,y,z);
printf("x=%d, y=%d, z=%d, result=%d\n",x,y,z,result);
}
