Loop in assembly doesn't work

Question

I had some problems when I tried to create a loop in asm. So I created another code with just the loop. The problem is, when I decrement or increment the ecx , the variable gets messed. If I use the loop instruction without the dec it doesn't work either. How do I use the ecx to loop?

Code

section .text
     global main

     extern printf
section .data
FORMAT: db "L", 10, 0 ; just to print the L 10 times
main:

     mov ecx, 10 ; start the counter in 10
     jmp runloop ; i imagine i dont need it
runloop:
     push FORMAT
     call printf
     add esp, 4
     dec ecx
     cmp ecx, 0
     jne runloop

Answer 1

ecx value is not guaranteed to be preserved across the printf call. Use one of the following registers instead: ebx , ebp , esi , edi . You should preserve them too by push ing the register of choise onto the stack and restoring it afterwards.