How to stop an infinite loop after a wrong input in a menu?

Question

i was making a menu with 3 int choices, if the input is a wrong int it reprints the menu and the input. The problem is that when instead of an integer the input is a char the program get stuck in an infinite loop, how can i solve this?

#include <stdio.h>
#include <stdlib.h>

int main(){
    
    int menu_choice;

do{
    printf("\n\t\t...PHALSOPHOBIA...\t\t");
    printf("\n\tMenu\t\n1. Imposta gioco.\n2. Gioca\n3. Termina gioco\n");

    scanf("%d", &menu_choice);

    switch (menu_choice)
        {
        case 1:
        break;

        case 2:
        break;

        case 3:
        break;

        default:
            printf("Comando errato.\n");
        }
}while (menu_choice < 1 || menu_choice > 3);
}

Answer 1

You need to clear the input buffer if it doesn't contain a digit, and you probably want to handle EOF:

#include <stdio.h>
#include <stdlib.h>

int flush() {
    for(;;) { int ch = getchar();
        if(ch == EOF || ch == '\n')
            return ch;
    }
}

int main(){
    int menu_choice;
    do {
        printf("\n\t\t...PHALSOPHOBIA...\t\t");
        printf("\n\tMenu\t\n1. Imposta gioco.\n2. Gioca\n3. Termina gioco\n");
        if(scanf("%d", &menu_choice) != 1) {
            if(flush() == EOF)
                break;
            menu_choice = 0;
        }
        switch (menu_choice) {
            case 1:
            case 2:
            case 3:
                break;
            default:
                printf("Comando errato.\n");
        }
    } while (menu_choice < 1 || menu_choice > 3);
}

example session:

                ...PHALSOPHOBIA...
        Menu
1. Imposta gioco.
2. Gioca
3. Termina gioco
x
Comando errato.

                ...PHALSOPHOBIA...
        Menu
1. Imposta gioco.
2. Gioca
3. Termina gioco
1

Consider introducing an enum so you constants to switch instead of just numbers.