Assembly help...

[Proto]

Ok as this month task i have to program the Hanoi towers in assembly... my only problem is that i pretty noobish in using extern function in asm files, so id ask for any advice you can give

My C++ calling program

#include [iostream.h]
#include [stdio.h]
#include [stdlib.h]

extern "C" int n;
extern "C" void principal();

int main(void){


cout <<"Numero de discos\n ";
cin >> n;

principal();


return 0;

}


The asm module

extern printf
global _n
global _principal

section .data
ind dd 0 ;;i use the indicator as a medium to know when to use the base ;; ;; case
_n dd 0
temp dd 0
fmt: db "se mueve %d del palo %d al palo %d", 10, 0

section .text

_principal

mov ax,1
mov bx,2
mov cx,3
mov dx,[_n]


Hanoi:
mov ax,1
cmp [ind],ax
JNZ general
push dx ;;base case, we move one disk from one stick to another
push ax
push cx
call printf ;;im asumming that the printf function gets the pops anyway ;; from what i've read

ret


ret ;;when we are done we return the control to C++

Code continues later about the general case

the error i am getting is


Linking...
proyecto.obj : error LNK2001: unresolved external symbol printf
Debug/Ensamblador.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

Ensamblador.exe - 2 error(s), 0 warning(s)

Any clues?

EDIT: aaa...nm i realized the mistake. it was _printf

[Proto]

Sorry for double posting but i have another problem. The printf function called from the asm doesnt... print anything Can you point me out any mistakes you see please

extern _printf
global _n
global _principal

section .data
ind dd 0 ;;con este sabremos si solo se va a mover un disco
_n dd 0 ;;numero de discos
temp dd 0
text: db "se mueve %d del palo %d al palo %d", 10, 0

section .text

_principal

mov ax,1
mov bx,2
mov cx,3
mov dx,[_n]
mov [ind],dx



Hanoi:
mov [temp],bx
mov bx,1
cmp [ind],bx
mov bx,[temp]
JNZ general
push dx
push ax
push cx
call _printf
pop bx
pop bx
pop bx
ret

ret ;;regresa al modulo de c++

general:
---------

[_hyde_]

Well, could be either one of the following things:

- You are not pushing the parameters used by printf in the right order (last argument ought to be pushed first).

- Also, I believe you are trying to print the string found inside text, but you haven't actually pushed a pointer to that string. Try something like this:

mov si, text ;stores the address of text in si
...
push si ;passes the parameter to the printf function.

Before you do any of this, however, remember to save the contents of things like bp, sp, si, and di (hell, you might as well just do a pusha right at the beginning of the function)

Hope this helps.

PS.: if you have any questions regarding assembly programming visit http://assembly.conforums.com/

EDIT: Like I thought, you only pushed *three* parameters instead of four!

[Proto]

....whoops

Yeah and i recover my registers later with a popa, the function that calls Hanoi.... thanks for your help

[Exophase]

I'm wondering why you're using the 16bit registers with 32bit data.. it'll work, if you don't overflow the 16bit space, but it still doesn't seem to make a lot of sense.

- Exo

[Proto]

Hmmm....i dont remember well...i guess it was because i was thinking that the pusha and popa only worked with the 16 bit part.... anyway im done with my code (it works now),here it is for those who need it (yeah sure )

extern	_printf
global _n
global _principal



section .data
ind dd 0  ;con este sabremos si solo se va a mover un disco
_n dd 0   ;numero de discos
temp dd 0

text db 'se mueve %d del palo %d al palo %d', 10, 0

section .text

_principal

mov ax,1  ;;se usan los registros para representar los palos
mov bx,2
mov cx,3 
mov dx,[_n]  ;;en dx se guarda el numero de discos
mov [ind],dx 



Hanoi:
mov [temp],bx
mov bx,1
cmp [ind],bx   ;;si ind vale uno es que solo se mueve un disco
mov bx,[temp]
JNZ general
pusha
push	ebp
mov	ebp,esp
mov [temp],cx
push  dword [temp]  ;;caso base Se lee: Se mueve el disco edx de eax a ecx

mov [temp],ax
push  dword [temp]

mov [temp],dx
push  dword [temp]

push dword text
call _printf
mov	esp,ebp
pop	ebp
popa
ret

ret ;;regresa al modulo de c++

general:
pusha            ;; movemos n-1 al palo auxiliar  
mov [temp], bx   
mov bx, cx
mov cx, [temp]
dec dx
mov [ind],dx
call Hanoi


popa             ;; uno al palo final
pusha
mov [temp],bx
mov bx,1
mov [ind],bx
mov bx,[temp]
call Hanoi


          ;;n-1 al palo central

popa
mov [temp], ax
mov ax, bx
mov bx, [temp]
dec dx
mov [ind], dx

call Hanoi
ret

[_hyde_]

Yea, I suppose you shouldn't really be using 16-bit regs to store 32-bit values. So, if you are just going to be entering 16-bit numbers to test your program, declare your vars as dw.