falling in segmentation fault in x86 assembly

Question

I am trying to print each charactere after a comma with printf, but it gives me segmentation fault

global main

extern printf

section .data
        num db "%d",0
        array db 2,4,3
        arrlen equ $ - array

section .text
main:
        mov ecx, 0

mainloop:
        cmp ecx, arrlen
        je exit

        movzx ebx, byte [array + ecx]
        push ebx
        push num
        call printf

        add esp, 8

        inc ecx
        jmp mainloop

exit:
        mov eax, 1
        xor ebx, ebx
        int 0x80

I tried even to use chatGPT xd

Answer 1

ECX is not a call-preserved register. printf probably modifies it so your ECX-based loop runs for too long, hence addressing memory beyond the array.
Try using EBX that is a call-preserved register:

main:
        xor   ebx, ebx
        jmp   beginloop
mainloop:
        movzx eax, byte [array + ebx]
        push  eax
        push  num
        call  printf
        add   esp, 8
        inc   ebx
beginloop:
        cmp   ebx, arrlen
        jb    mainloop
exit:
        mov   eax, 1
        xor   ebx, ebx
        int   0x80