Question

I was writing this code on codeblocks(only compiler I m having).When I encountered such a behaviour. plz Somebody suggest why is this happening with ct, am I missing something.

#include <stdio.h>
int main(int argc,char* argv[])
{
    int lov[3][2]={0};        
    int ct=0;
    char* art;
    if(argc!=4)
        return 1;   


   art=argv[1];
        do
        {
            if(*art=='L' & *(art+1)=='o' & *(art+2)=='c')
            {
                printf("\n\n (art+3)=%s ,*(art+3)=%c ,*(art+5)=%c",(art+3),*(art+3),*(art+5) );
                lov[ct][ct]=*(art+3)-48;
                lov[ct][ct+1]=*(art+5)-48;
                printf("\nct=%d,lov[x][x]=%d,lov[x][x+1]=%d ",ct,lov[ct][ct],lov[ct][ct+1]);
                ct++;
            }
            art+=3;
        }
        while(*(art++));
getchar();
}

And on command prompt:-

>Resol.exe Loc2,5 Loc3,8 Loc5,4
Output:-


 (art+3)=2,5 ,*(art+3)=2 ,*(art+5)=5
ct=0,lov[x][x]=2,lov[x][x+1]=5

 (art+3)=3,8 ,*(art+3)=3 ,*(art+5)=8
ct=1,lov[x][x]=3,lov[x][x+1]=8

 (art+3)=5,4 ,*(art+3)=5 ,*(art+5)=4

ct=5,lov[x][x]=4198582

,lov[x][x+1]=4

Why ct becomes 5????(last Line)

Answer 1

It would appear that ct is being overwritten because you are accessing lov out of bounds. Your compiler is probably placing ct and lov close to each other on the stack which is why ct is being modified incorrectly.

When ct equals 1 you write to lov[ct][ct+1], which is lov[1][2]. That is out of bounds. But the next time round you write to lov[2][2] and lov[2][3] and one of those will be the one that causes the modification to ct.

When you write lov[ct][ct+1], that can only be valid for ct == 0. All other values of ct result in out-of-bounds access of the array.

I would not be surprised if there are other such errors given the confusing nature of this code.