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 pushing the register of choise onto the stack and restoring it afterwards.