cin for an int inputing a char causes Loop that is supposed to check input to go wild

buffer, c++, char, cin, int

Solution

When an error occurs when reading from a stream, an error flag gets set and no more reading is possible until you clear the error flags. That's why you get an infinite loop.

cin.clear(); // clears the error flags
// this line discards all the input waiting in the stream
cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');

Also, it's wrong to use the results of input operation if you don't know whether the read succeeded in the first place. You can't make assumptions about the value of `iAuswahl`. That's one of most often made errors by newbies using streams. Always check if the input operation was ok. This is most easily done by using `operator>>` in boolean context:

if (cin >> some_obj) {
    // evaluates to true if it succeeded
} else {
    // something went wrong
}

And, my oh my, this line

while (iAuswahl != 1 && iAuswahl != 2 && iAuswahl != 3 && iAuswahl != 4 && iAuswahl != 5 && iAuswahl != 6 && iAuswahl != 7 && iAuswahl != 8 && iAuswahl != 9)

can be just this:

while (iAuswahl < 1 || iAuswahl > 9)

A correct loop could look something like this:

while (true)
{
    if ((cin >> iAuswahl) && (iAuswahl >= 1) && (iAuswahl <= 9)) break;
    std::cout << "error, try again\n";
    cin.clear();
    cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}

Problem

This is a function of my game it will ask for input and cin into "iAuswahl"! Then the while loop is checks if it is one of the Values i want 1-9 if not it activates and is supposed to ask for new input. Witch it does for int. But if i input a char like r it will go crazy and just keep giving me back my cout and skip the cin! My questions are why does it do it and how do i stop it? ``` void zug(string sSpieler, int iDran){ int iAuswahl; char cXO = 'O'; if (iDran == 1) { cXO = 'X'; } cout << sSpieler << ", Sie sind am Zug. Bitte waehlen sie eins der Felder.\n" << endl; grafik(); cout << "Sie sind >> " << cXO << " <<." << endl; cin >> iAuswahl; cout << endl; while ( iAuswahl != 1 && iAuswahl != 2 && iAuswahl != 3 && iAuswahl != 4 && iAuswahl != 5 && iAuswahl != 6 && iAuswahl != 7 && iAuswahl != 8 && iAuswahl != 9 ) { cout << "Kein gültiges Feld bitte wählen sie noch einmal!\n" << endl; cin >> iAuswahl; } feldfuellen(iAuswahl, cXO); } ```

Original source