在C中输入字符时代码循环

Question

这主要是出于好奇,为什么会发生这种情况,因为在我的情况下并不重要.如果我键入一个无效的数字,它会正确地转到重复标签并要求我再次输入一个数字,但如果我输入一个像'f'这样的字符,它将无休止地循环而不会停止.为什么是这样？

这里的数组和所有变量都是int类型.

    repeat: 
    printf("Enter number of available space, you are %c: ", userXO);
    scanf("%d", user);

    switch (*user)
    {
        case 1: if (spaces[0][0] == 49){ spaces[0][0] = userXO;}else goto repeat; break;
        case 2: if (spaces[0][1] == 50){ spaces[0][1] = userXO;}else goto repeat; break;
        case 3: if (spaces[0][2] == 51){ spaces[0][2] = userXO;}else goto repeat; break;
        case 4: if (spaces[1][0] == 52){ spaces[1][0] = userXO;}else goto repeat; break;
        case 5: if (spaces[1][1] == 53){ spaces[1][1] = userXO;}else goto repeat; break;
        case 6: if (spaces[1][2] == 54){ spaces[1][2] = userXO;}else goto repeat; break;
        case 7: if (spaces[2][0] == 55){ spaces[2][0] = userXO;}else goto repeat; break;
        case 8: if (spaces[2][1] == 56){ spaces[2][1] = userXO;}else goto repeat; break;
        case 9: if (spaces[2][2] == 57){ spaces[2][2] = userXO;}else goto repeat; break;
        default: goto repeat; break;
}

Answer 1

scanf("%d", user);尝试读取一个数字,找到一个char(f),将其留在缓冲区中并结束.循环然后循环并scanf("%d", user);再次执行.然后再次...