In this article, we will first write a small piece of code in C that assigns values to variables. Then, we will analyze the corresponding x86 assembly code. We will also learn through another example how to construct C code from x86 assembly that assigns values to variables.

Let’s first write a small piece of code in C:

#include <stdio.h>
int main() {
        int a = 1;
        return 0;
}

This piece of code assigns the value 1 to a variable named a. Now, let’s try to compile the code and get the corresponding assembly code.

$ gcc -c variables.c
$ objdump -M intel -d variables.o

Please note that the “-M intel” option will generate the assembly code in the Intel syntax.

0000000000000000 <main>:
   push   rbp
   mov    rbp,rsp
   mov    DWORD PTR [rbp-0x4],0x1
   mov    eax,0x0
   pop    rbp
   ret   

As we discussed in one of our previous articles, the first two instructions are part of the function prologue. They are executed every time a function is called. The RBP register points to the base of the stack frame and we access all the function parameters and the local variables using the …