处理输入时意外冻结

Question

I've been trying to handle multiple functions which the user can select from, but for some reason, unexpected input isn't causing the developed reaction, freezing instead.

int main(){
    int done = 0, isModeValid = 1;
    char nextMode[15], *options[] = {"quit",  "test", "getASCII"};

    while(done == 0){
        cls();
        isModeValid = 0;
        text(1);
        currentOptions(options);
        gets(nextMode);
        int i = 0;
        for(i = 0; i < (sizeof(options)); i++){
            if(strcmp(nextMode, options[i]) == 0){
                 done = runMode(i);
                 break;
            }
            //Error seems to happen after this point
            if(strcmp(nextMode, options[i]) != 0 && i == sizeof(options)){
                cls();
                text(3);
                Sleep(750);
            }
        }
    }
    return 0;
}
void cls(){
    system("cls");
}

Answer 1

You are invoking undefined behaviour. sizeof yields the size of the argument in bytes / char s, not the length of the array. So you are iterating over more elements than the array actually contains and try to access elements past its bounds.

Use sizeof(options) / sizeof(options[0]) to get the length independent from the type of each entry.

Note: Declaring the array static would make its allocation and initialization before main is called. Your current version will do that each time the function is called. While uncritical for main , it will be significant for other functions which are called more than once.

Answer 2

To get the number strings in options , you need (sizeof(options)/sizeof(options[0])) , not just sizeof(options) ... so your for loop is looping too many times, and you're accessing out of bounds.

Also, your second if never executes because i will never get to sizeof(options) .