Why is control + P leading to infinite loop in C++ (Visual Studio)? - c++

Question

I've been programming for a while (in Prolog, Scheme, and a little bit in C), but I recently decided to brush up on my C++ knowledge. I solved a problem that was meant to illustrate vectors. It was essentially a project to create a database that creates a vector to temporarily store the various games that the user inputs into it, and removes the ones they don't want. The code itself is running fine, not as pretty as scheme or Prolog could do it, but it works.
However, I accidentally typed "Control P" into the first prompt of the program and I got the strangest result: it started an infinite loop. I tried it again with "Control Z" and I got the same result. I haven't tried any other key combos, but I imagine that some others could be found. It's not a super worrying problem, but I am curious to know why it's doing this. Is it something about C++, or is it just Visual Studio? Anyway, here's the source:
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
cout << "Welcome to the Cpp Games Database!";
int x = 0;
string game = "";
vector <string> games;
vector <string>::const_iterator iter;
while (x != 4){
cout<< "\n\nPlease choose from the list bellow to decide what you want to do:\n";
cout<< "1. Add Games to the Database.\n"
<< "2. Remove Games from the Database.\n"
<< "3. List all the Games.\n"
<< "4. Exit.\n"
<< "\n(Type the number of your choice and hit return)\n";
cin >> x;
switch (x){
case 1:
game = "";
do{
cout << "\nPlease Input a Game (type esc to exit): ";
cin >> game;
games.push_back(game);
} while (game != "esc");
games.pop_back();
break;
case 2:
game = "";
do{
cout << "\nPlease input the game you would like to remove(or type esc to exit): ";
cin >> game;
iter = find(games.begin(), games.end(), game);
if(iter != games.end())
games.erase(iter);
else cout << "\nGame not found, try again please.\n";
} while (game != "esc");
break;
case 3:
cout << "\nYour Games are:\n";
for (iter = games.begin(); iter != games.end(); iter++)
{
cout << endl << *iter << endl;
}
break;
default: break;
}
}
return 0;
}

Answer 1

Since you are not inputting valid data for cin it is stuck there waiting for the data to be reprocessed or discarded for new input. You need to check your input and only accept valid data. Essentially cin is keeping the original data it's given and continuously trying to process it.
Always verify your input and discard it if it's invalid.
Here is another answer on the same problem for some more insight (with source).
https://stackoverflow.com/a/17430697/1858323