Project Euler with C++ - compiler won't process after 100 x 101

I've started working with C++ and was fiddling around with some problems on projecteuler.net.

I'm on question #4 and here's my code:

algorithm to check whether the number is a palindrome:

bool forwardCheck(long posPal){
long n = posPal;
long rev = 0;
long dig;

    while (posPal > 0){
        dig = posPal % 10;
        rev = rev * 10 + dig;
        posPal = posPal % 10;
    }

    return n == rev;
}

main program:

int main(){
long palindrome;

cout << "We are finding the largest palindrome made from two 3-digit numbers.\n"
     << "Calculating...\nCalculating..开发者_Go百科.\nDone!\n";

for (long i = 100; i < 1000; i++){
    for (long j = 100; j < 1000; j++){
        long mult = i * j;
            if (forwardCheck(mult)){
                palindrome = mult;
                //testing function above
                cout << mult << " is a palindrome!\n";
            } else
                //testing function above
                cout << mult << " is not a palindrome...\n";
    }
}


cout << "The largest palindrome composed of two 3 digit numbers is: " << palindrome
     << endl;

return 0;
}

I'm using X11 on OS X as my compiler with g++ and my problem is that, using the code above, the numbers get to 101,000 as the multiple and then stops and stalls after that. My question is:

Why is it doing this? Am I approaching this inefficiently?

I realize that an alternative is to start from long = 999 and iterate downwards but I've coded but it gets stuck after the "Done!" statement (yes, I know it's a bit ambitious to program that in before the algorithm has run but I like to be optimistic. :)

By stuck and stalls, I mean that the CPU usage spikes but nothing is written to the console.

As a general side note:

Is there a way I can debug through the console, i.e. have it tell me what it's doing similar to echo in windows command prompt? I'm new to OS X too...

Have a look at this code:

  while (posPal > 0){
    dig = posPal % 10;
    rev = rev * 10 + dig;
    posPal = posPal % 10;
  }

I think you are miscalculating posPal at the bottom of the loop.

Try replacing with posPal = posPal / 10.

seems that it should be posPal = posPal / 10

e.g. starting with 123 you want to use 3 for building an inverse number and to move to 12