Ben Eater: Comparing C to Machine Language

Ben Eater

macOS Sierra: otool (Object File Displaying Tool) Example

Command:

$ cat fib.c


Result:

#include <stdio.h>

int main(void){
int x, y, z;

while (1) {
x = 0;
y = 1;
do {
printf("%d\n", x);

z = x + y;
x = y;
y =z;
} while (x < 255);
}
}


Command:

$ gcc -o fib fib.c
$ otool -tv fib


Result:

fib:
(__TEXT,__text) section
_main:
0000000100000f30 pushq %rbp
0000000100000f31 movq %rsp, %rbp
0000000100000f34 subq $0x20, %rsp
0000000100000f38 movl $0x0, -0x4(%rbp)
0000000100000f3f movl $0x0, -0x8(%rbp)
0000000100000f46 movl $0x1, -0xc(%rbp)
0000000100000f4d leaq 0x56(%rip), %rdi
0000000100000f54 movl -0x8(%rbp), %esi
0000000100000f57 movb $0x0, %al
0000000100000f59 callq 0x100000f88
0000000100000f5e movl -0x8(%rbp), %esi
0000000100000f61 addl -0xc(%rbp), %esi
0000000100000f64 movl %esi, -0x10(%rbp)
0000000100000f67 movl -0xc(%rbp), %esi
0000000100000f6a movl %esi, -0x8(%rbp)
0000000100000f6d movl -0x10(%rbp), %esi
0000000100000f70 movl %esi, -0xc(%rbp)
0000000100000f73 movl %eax, -0x14(%rbp)
0000000100000f76 cmpl $0xff, -0x8(%rbp)
0000000100000f7d jl 0x100000f4d
0000000100000f83 jmp 0x100000f3f