Question

I’m running a C++ Program that is supposed to convert string to hexadecimals. It compiles but errors out of me at runtime saying:

Debug Assertion Failed! (Oh no!)

Visual Studio2010\include\xstring

Line 1440

Expression: string subscript out of range

And I have no choice to abort… It seems like it converts it though up to the point of error so I’m not sure what’s going on. My code is simple:

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main()
{
    string hello = "Hello World";
    int i = 0;
    while(hello.length())
    {
        cout << setfill('0') << setw(2) << hex << (unsigned int)hello[i];
        i++;
    }

    return 0;
}

What this program should do is convert each letter to hexadecimal – char by char.

Answer 1

Your while condition is incorrect:

while(hello.length())

The loop never terminates and i becomes large (more than string length minus one) and when you access the string at that index you get runtime assertion.

Change it to:

while(i < hello.length())

Or better use iterators.