Interesting Error

I was writing a small program just to mess around and suddenly I got an error that

Quote:

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Run-Time Check Failure #2 - Stack around the variable 'letter' was corrupted.

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I was wondering what causes them, and kinda what do they indicate?

Here is the entire offending code...

Code:

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#include "stdafx.h"
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <sstream>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
        stringstream st;
        srand( (unsigned)time(NULL) );
        for( int i = 0; i < 256; i++ )
        {
                int num = rand() % 65;
                num += 65;
                char letter;
                itoa( num, &letter, 10 );
                st << letter;
        }
        string theString = st.str();

        cout << theString << endl;
        return 0;
}

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Perhaps I am just tired(which I am) but I see nothing wrong with it. If anyone could enlighten me, perhaps you can help my tired eyes see what I am doing wrong. Thanks.

what compiler are you using? I used VC++ 6.0, changed _tmain to main and TCHAR to char. Your program ran without error on XP.

Edit: I could swear this was on the C board. I believe itoa was incorrectly used. It takes a numerical value and stores it as a string into a buffer you give it, which you only passed a reference to a char as.

Simple solution: no need for itoa

Code:

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#include <iostream>
#include <cstdlib>
#include <ctime>
#include <sstream>
using namespace std;

int main(int argc, char* argv[])
{
        stringstream st;
        srand( (unsigned)time(NULL) );
        for( int i = 0; i < 256; i++ )
        {
                char letter = (rand() % 65) + 65;
                st << letter;
        }
        string theString = st.str();

        cout << theString << endl;
        return 0;
}

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Hmm thats right, forgot you could create a letter with a number it converts automatically.

As for compiler using VC .net 2003.

Still wondering exactly what that error means and how it happens, but thanks tonto, much easier! :)

Quote:

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Originally Posted by dpro

Hmm thats right, forgot you could create a letter with a number it converts automatically.

As for compiler using VC .net 2003.

Still wondering exactly what that error means and how it happens, but thanks tonto, much easier! :)

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as tonto pointed out, the function was expecting a null-terminated string, and you were passing it a pointer to a single char. So at runtime, the function couldn't find the end of the string causing undefined behavior. I guess VC++ 6.0 is more forgiving and doesn't catch many errors.

Quote:

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Originally Posted by Ancient Dragon

as tonto pointed out, the function was expecting a null-terminated string, and you were passing it a pointer to a single char. So at runtime, the function couldn't find the end of the string causing undefined behavior. I guess VC++ 6.0 is more forgiving and doesn't catch many errors.

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Oh, duh! Sorry, was totally missing the point, I see you are right, thanks for pointing me in the right direction!