miamiruby / fib Goto Github PK

# Fibinacci in c
# https://en.wikipedia.org/wiki/Fibonacci_number
# Build fib.c
gcc -o fib fib.c

# Decompile Compiled File to Assembly
otool -tv fib

# variables
# 0x8 = x
# 0xc = y
# 

# Result
fib:
(__TEXT,__text) section
_main:
#Setup 
0000000100000f30    pushq    %rbp                # ?
0000000100000f31    movq    %rsp, %rbp           # ?
0000000100000f34    subq    $0x20, %rsp          # ?
0000000100000f38    movl    $0x0, -0x4(%rbp)     # ?
# Starting Setting Values
0000000100000f3f    movl    $0x0, -0x8(%rbp)     # set x = 0
0000000100000f46    movl    $0x1, -0xc(%rbp)     # set y = 1
# printf x
0000000100000f4d    leaq    0x56(%rip), %rdi
0000000100000f54    movl    -0x8(%rbp), %esi     # print x
0000000100000f57    movb    $0x0, %al
0000000100000f59    callq    0x100000f88
# z = x + y
0000000100000f5e    movl    -0x8(%rbp), %esi
0000000100000f61    addl    -0xc(%rbp), %esi
0000000100000f64    movl    %esi, -0x10(%rbp)
# x = y
0000000100000f67    movl    -0xc(%rbp), %esi
0000000100000f6a    movl    %esi, -0x8(%rbp)
# y = z
0000000100000f6d    movl    -0x10(%rbp), %esi
0000000100000f70    movl    %esi, -0xc(%rbp)
# ??
0000000100000f73    movl    %eax, -0x14(%rbp)
# compaire 255 to x
0000000100000f76    cmpl    $0xff, -0x8(%rbp) 
# jump if less then 255 jump to f4d
0000000100000f7d    jl    0x100000f4d
# jump back to while(1)
0000000100000f83    jmp    0x100000f3f