Getting input without newline

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venomxxl venomxxl is offline Offline
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Getting input without newline

 
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  #1
Feb 2nd, 2009
Hello everyone,
I started learning assembly yesterday. Yes maybe I chose a wrong guide but I have a little problem here. It's about getting some integers without a newline. That is probably very easy to solve but I was searching for a solution for a few hours and no results. Well, enough about that, let's get to the point.
I need to get an input cointaining some integers, but I need them to be without a newline. I wrote a small loop to do that for me, I think everything is OK, yet it gives me a "Segmentation fault".

CPU: i486
Assembler: NASM version 0.99.06-20071101
OS: Ubuntu 8.04 (Hardy)
Linux kernel: 2.6.24-22-generic

Commands:
nasm -f elf kalkulator.asm
ld -s -o kalkulator kalkulator.o
asm Syntax (Toggle Plain Text) 
  1. %define  lf  10
  2.  
  3. bufor1: times  40  db  0
  4. bufor2: times  40  db  0
  5.  
  6. wczytuj:
  7.         xor     esi, esi
  8.         mov     esi, 0
  9.  
  10.         petla:
  11. 	push	eax
  12. 	push	ebx
  13. 	push	ecx
  14. 	push	edx
  15.  
  16. 	mov	eax, 3		
  17. 	mov	ebx, 0	
  18. 	lea	ecx, [bufor1]
  19. 	mov	edx, 1
  20. 	mov     al, [bufor1]
  21.  
  22.         cmp     al, lf
  23.         jne     _wczytuj_zapisz
  24.  
  25.         push    esi
  26.         push    eax
  27. 	int	80h
  28.  
  29.         pop     eax
  30.         pop     esi
  31. 	pop	edx
  32. 	pop	ecx
  33. 	pop	ebx
  34. 	pop	eax
  35.  
  36.         cmp     al, lf
  37.         jne     petla
  38.  
  39.         ret
  40.  
  41. _wczytuj_zapisz:
  42.         mov     [bufor2+esi], al
  43.         inc     esi
  44.         ret

Note that I am a complete newbie in assembly, so please try to explain my mistakes as precisely and as easy to understand as possible. I'd be happy if you correct the whole code, but I'll accept any help.

Thanks
-Marek
Last edited by venomxxl; Feb 2nd, 2009 at 12:45 pm.
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Re: Getting input without newline

 
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  #2
Feb 2nd, 2009
I believe the code listed below is giving you oyur segmentation fault.
When the branch is taken you are not poping your stack and the return address is burried under everything you pushed. You should change your label to. It should be something short but descriptive. A lot of people won't even take time to look at code if it is confusing.

Assembly Syntax (Toggle Plain Text) 
  1. cmp     al, lf        
  2. jne     _wczytuj_zapisz
Assembly Syntax (Toggle Plain Text) 
  1. wczytuj_zapisz:        
  2. mov     [bufor2+esi], al        
  3. inc     
  4. esi        ret
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