In this article, we will learn how to construct C code from x86 assembly that involves arrays. The article is divided into two parts. In the first part, we will write C code and analyze the corresponding x86 assembly code. In the second part of the article, we will look into x86 assembly code and try to construct the corresponding C code that involves arrays.

Let’s write the following piece of C code first.

#include <stdio.h>
int main() {
        int array[2];
        array[0] = 1;
        array[1] = 2;
        return 0;
}

Now, let’s compile the above code and look into the corresponding assembly code using the objdump command.

$ gcc array1.c
$ objdump -M intel -d a.out

The x86 assembly code will look like the following:

0000000000400546 <main>:
  400546:	push   rbp
  400547:	mov    rbp,rsp
  40054a:	sub    rsp,0x10
  40054e:	mov    rax,QWORD PTR fs:0x28
  400555:	00 00 
  400557:	mov    QWORD PTR [rbp-0x8],rax
  40055b:	xor    eax,eax
  40055d:	mov    DWORD PTR [rbp-0x10],0x1
  400564:	mov    DWORD PTR [rbp-0xc],0x2
  40056b:	mov    eax,0x0
  400570:	mov    rdx,QWORD PTR [rbp-0x8]
  400574:	xor    rdx,QWORD PTR fs:0x28
  40057b:	00 00 
  40057d:	je     400584 <main+0x3e>
  40057f:	call   400420 <__stack_chk_fail@plt>
  400584:	leave  
  400585:	ret    
  400586:	nop    WORD PTR cs:[rax+rax*1+0x0]
  40058d:	00 00 00