使用 scanf 检查错误

Question

对于我的作业，用户输入 5 个介于 1 和 9 之间的整数来表示五个 9 面骰子，然后用于计算分数。我们还需要能够检测无效输入，即 1-9 之间的 5 个整数以外的任何内容。问题是，当我为我的任务运行自动测试时，当输入少于 5 个东西时，我会收到运行时错误。

我的错误检查代码是（忽略 countArray 的东西，稍后在程序中使用）：

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

#define TRUE 1
#define FALSE 0

#define ARRAY_SIZE 5

...

int main(void) {

    int numbers[ARRAY_SIZE];
    int scanFail = 0;

    int i = 0;

      ...

      // Check for if 5 integers between 1 and 9 have been entered

    while (i < ARRAY_SIZE && scanFail == FALSE) {

        if (scanf("%d", &numbers[i]) != 1) {
            scanFail = TRUE;
        }

        if (numbers[i] < 1 || numbers[i] > 9) {
            scanFail = TRUE;
        }

        countArray[i] = ARRAY_NOT_COUNTED;
        i++;

    }

    if (scanFail == TRUE) {
        printf("Invalid Input: 5 integers 1..9 must be supplied.\n");
        return EXIT_FAILURE;
    }

    ...

自动测试是这样说的：

  Test10 (1 2 3) - failed (errors)

  Your program produced these errors:

  Runtime error: uninitialized variable accessed.

  Execution stopped here in main() in youChew.c at line 65:

  \t\t}
  \t\t
  -->\t\t if (numbers[i] < 1 || numbers[i] > 9) {
  \t\t    scanFail = TRUE;
  \t\t}

  Values when execution stopped:

  i = 3
  numbers = {1, 2, 3, 69513217, -22336628}
  scanFail = 1
  numbers[i] = 69513217

  Test 11 (potato) - failed (errors)

  Your program produced these errors:

  Runtime error: uninitialized variable accessed.

  Execution stopped here in main() in youChew.c at line 65:

  \t\t}
  \t\t
  -->\t\t if (numbers[i] < 1 || numbers[i] > 9) {
  \t\t    scanFail = TRUE;
  \t\t}

  Values when execution stopped:

  i = 0
  numbers = {69515968, 0, 8192, 69513217, -18240628}
  scanFail = 1
  numbers[i] = 69515968

我不确定如何修复它，因此感谢您的帮助。

Answer 1

恕我直言，立即打破循环通常会产生比维护标志更具可读性的代码..

在您的情况下，问题是如果 scanf 失败，您还没有读取数字，但您想检查它（未初始化的值）是否在 1 和 9 之间。该测试甚至不应该发生。 快速失败。