int2str problem

devit · 05-11-2004, 11:05 AM

I tried to make a program that converts an integer to a string (for nasm) but I get an error(Floating point exception) because of the "div edx". Do you have any idea how to solve that?

Code:

section .data
numar:	resw	1
string:	resb	6
msg1:	db	"15 => "
len_msg1	equ	$ - msg1
len_string:	resb	4	
	
section .text
	global _start


int2str:			; eax = number to convert, di = the result(string)
	pusha
	mov	ebx,1
	mov	cx,0
iar:	
	mov	edx,10
	div	edx	;there is a problem
	mov	[di],edx
	mov	bx,48
	add	[di],bx
	mov	bx,0
	inc	di
	inc	cx
	cmp	eax,ebx
	jne	iar
	mov	bx,0xa
	mov	[di],bx
	popa
	mov	eax,ecx
	ret

exit:
	mov	eax,1
	int	0x80
	
_start:
	mov	edx,len_msg1
	mov	ecx,msg1
	mov	ebx,1
	mov	eax,4
	int	0x80

	lea	di,[string]
	mov	eax,15
	call	int2str
	mov	edx,eax
	mov	ecx,string
	mov	ebx,1
	mov	eax,4
	int	0x80

	call exit

Thanks!

The_Nerd · 05-11-2004, 11:54 AM

Is there any reason you can't use the stdlib function, itoa???

arvind_sv · 05-11-2004, 01:07 PM

Hi,

Read the nasm man page.

Usage: div <operand>

* 32 bit operand: (which edx is): EDX:EAX is divided by the given operand. So, if you set EDX to 10, then, obviously EDX:EAX goes out of bounds. Try something like this:

mov ebx, 10
div bx

Also, DI is not initialized. It's not recommended to use [di] before that. I think you want this:
mov di, bx

You're also trying to use edx later (after div, as "mov [di], edx"). What are you trying to achieve? You do know that edx would have been unchanged even if "div edx" had worked, don't you?

Arvind

devit · 05-11-2004, 01:59 PM

I like the idea of using itoa from stdlib but how could I implement this?

The_Nerd · 05-12-2004, 01:18 PM

Well... If all your code is asm, I don't know how you could implement itoa. If not however, its easy.
I am sorry, I am not too much help here, because I know nothing (or very little) of asm.