Go4Expert - unexpected output

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- - unexpected output (http://www.go4expert.com/showthread.php?t=18570)

kaushalneo

17Jul2009 00:30

unexpected output

please xplain the output of following program....

Code:

#include<iostream.h>

#include<conio.h>

#include<string.h>



void main(){

        char a[10];

        char b[10];

        char c[10];

        cin>>c;

        cin>>b;

        strcpy(a,c);

        cout<<a<<endl;

        strcat(b,c);

        cout<<b<<endl;

        cout<<a<<endl;

        int x=strcmp(a,c);

        cout<<x;

}

please xplain the output of the above program...

kaushal
swapnil
kaushal
swapnilkaushal
shal
8

xpi0t0s

17Jul2009 01:50

Re: unexpected output

You have undefined behaviour, because b is not long enough for "swapnil"+"kaushal" - total 15 characters, but b is only 10 chars long.

So anything could happen, and the solution to the problem is to extend b to at least 15 characters so that it can cope with what you want to do. Or use strings so you can do b+=c without worrying about buffer sizes.

This is a buffer overflow bug.

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