Question

I tryed looking up things that have to do with setting a variable that is already set causing a crash and I found nothing on-topic for this.

Rextblock is a user input number. Returns random number between numbermax and 2 if textblock is equal to 1.

if ( textblock == 1 )
{
   int rand1 = rand() %(numbermax - 2) + 2;
   int textbox = rand1;
}

When I input 1 for textblock it crashes, i’m pretty sure this code is causing it.

using namespace std;

int main(int argc, char *argv[])
{
srand(time(NULL));


int numbermax = 2;



while (while1 < 1)    
{   
cout << "input the number of the text block you wish to use, \n ";
int textblock;
cin >> textblock;

if ( textblock != 0 )
{

}

if ( textblock == 1 )
{
   int rand1 = rand() %(numbermax - 2) + 2;
   int textbox = rand1;
}

if (textblock == 2)
{

}

if (textblock == 2)
{

}


if( textblock == 0 )
{

}   

if ( textblock == 1 )
{
   cout << " \n error, try again \n";     
}

Answer 1

I highly suspect that when you run it, numbermax is equal to 2. This would cause numbermax - 2 to equal zero, and using modulus with a rhs of 0 invokes division by 0, which is undefined behaviour, hence the fair probability of a crash.

You should be making sure that it doesn’t end up doing that via a check of if (numbermax != 2).