LMat619 0 Newbie Poster

Hi everyone. I'm having a little trouble trying to debug this code I made. What I am trying to do is add two numbers each up to 255 decimals.

What I did was put the numbers (input by the user) into a string, convert it to BCD, add them, convert it back to ASCII, and print the result. When I try to run my program it either crashes or gives me a random number.

Any help would be appreciated. Thanks.

This is my main function:

#include <stdio.h>
#include <stdlib.h>

extern void addLarge(char *number1, char *number2, char *result);
int main(int argc, char *argv[])
{
 unsigned char number1[256];
 unsigned char number2[256];
 unsigned char result[256];
 puts("number 1: ");
 gets(number1);
 puts("number 2: ");
 gets(number2);
 addLarge(number1, number2, result);
 printf("The result is : %d\n", result);
 system("PAUSE");	
 return 0;
}

This is the assembly function

.global _addLarge
_addLarge:
    pushl %ebp
    movl %esp, %ebp
    call _rightalignfirst
    call _rightalignsecond
    call _convascii
    call _addnumbers
    call _convbcd
    movl %ebp, %esp
    popl %ebp
    ret

.global _rightalignfirst
_rightalignfirst:
    pushl %ebp
    movl %esp, %ebp
	movl 8(%ebp), %ebx
	xor %esi, %esi
	xor %eax, %eax
	movl $255, %edi
loop0:
	cmpb $0, (%ebx, %esi, 1)
	je loop1
	inc %esi
	movl %esi, %edx
	cmpl $255, %esi
	jge loop1
	jmp loop0
loop1:
	cmpl $-1, %esi
	jle loop2
	movb (%ebx, %esi, 1), %al
	movb %al, (%ebx, %edi, 1)
	dec %esi
	dec %edi
	jmp loop1
loop2:
	movl $255, %edi
	subl %edx, %edi
	subl $2, %edi
loop3:
	cmpl $-1, %edi
	jle faldone
	movb $0, (%ebx, %edi, 1)
	dec %edi
	jmp loop3
faldone:
	popl %ebp
	ret

.global _rightalignsecond
_rightalignsecond:
    pushl %ebp
    movl %esp, %ebp
	movl 12(%ebp), %ecx
	xor %esi, %esi
	xor %eax, %eax
	movl $255, %edi
back0:
	cmpb $0, (%ecx, %edi, 1)
	je back1
	inc %esi
	movl %esi, %edx
	cmpl $255, %esi
	jge back1
	jmp back0
back1:
	cmpl $-1, %esi
	jle back2
	movb (%ecx, %esi, 1), %al
	movl %eax, (%ecx, %edi, 1)
	dec %esi
	dec %edi
	jmp back1
back2:
	movl $255, %edi
	subl %edx, %edi
	subl $2, %edi
back3:
	cmpl $-1, %edi
	jle saldone
	movb $0, (%ecx, %edi, 1)
	dec %edi
	jmp back3
saldone:
	popl %ebp
	ret

.global _convascii
_convascii:
    pushl %ebp
    movl %esp, %ebp
	xor %esi, %esi
convone:
	cmpl $255, %esi
	jge parttwo
	subb $30, (%ebx, %esi, 1)
	inc %esi
	jmp convone
parttwo:
	xor %esi, %esi
convtwo:
	cmpl $255, %esi
	jge convasciidone
	subb $30, (%ecx, %esi, 1)
	inc %esi
	jmp convtwo
convasciidone:
	popl %ebp
	ret

.global _addnumbers
_addnumbers:
    pushl %ebp
    movl %esp, %ebp
	movl $255, %esi
	xor %edx, %edx
	xor %edi, %edi
addthem:
	cmpl $-1, %esi
	jle adddone
	movb (%ebx, %esi, 1), %dl
	addb (%ecx, %esi, 1), %dl
	addl %edi, %edx
	movb %dl, (%eax, %esi, 1)
	cmpb  $9, (%eax, %esi, 1)
	jle notover
	subb $10, (%eax, %esi, 1)
	movl $1, %edi
	dec %esi
	jmp addthem
notover:
	xor %edi, %edi
	dec %esi
	jmp addthem
adddone:
	popl %ebp
	ret

.global _convbcd
_convbcd:
    pushl %ebp
    movl %esp, %ebp
	movl $255, %esi
	dec %esi
	xor %edi, %edi
conv:
	cmpl %esi, %edi
	jge convbcddone
	addb $30, (%eax, %edi, 1)
	inc %edi
	jmp conv
convbcddone:
        movl %eax, 16(%ebp)
	pop %ebp
	ret
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