进程过早退出 C 编程

Question

有一部分程序要求用户输入 Y 或 N 然后当我选择 N 时循环返回，否则它将结束while循环并继续。当我第一次选择 Y 时，程序运行正常，但是当我选择 N 然后在我的程序退出后选择 Y 时，即使它确实如此没有遇到来自 main 的 return 关键字 它以垃圾return 值退出。它停在system("cls");。谁能告诉我这段代码有什么问题。笔记： Statistician 是我用 typedef 创建的整数指针类型。而且，我还在 survey.h 文件中声明了 SIZE 变量

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include "survey.h"

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char *argv[]) {

    SIZE = 10;
    int c, count = 0, item = 0;
    Statistician arr;
    float mea, med;

    arr = (int*)calloc(10, sizeof(int));

    printf("Enter 10 answers\n");

    while(count < SIZE) // this is the while loop that loops until Y is chosen by the user in the add function
    {
        while(item > 9 || item < 1)
        {
            scanf("%d", &item);
        }

        ++count;
        add(arr, &count, &SIZE, item);
        item = 0;
    }
    system("cls");
    mea = mean(arr, count);
    med = median(arr, count);
    printf("mean = %f\n", mea);
    printf("median = %f\n", med);

    return 0;
}

add()函数的定义：

void add(Statistician answer, int *count, int *SIZE, int item)
{

    int i, j, temp;
    bool swapped;
    char choice;
    
    answer[*count - 1] = item;

    for(i = 0; i < *count - 1; i++)
  {
    swapped = false;
    for(j = 0; j < *count - i - 1; j++)
    {

      if(answer[j] > answer[j + 1])
      {
        temp = answer[j];
        answer[j] = answer[j + 1];
        answer[j + 1] = temp;
        swapped = true;
      }

    }

  if(swapped == false)
  break;
  }

  if(*count == *SIZE)
    {
        printf("Array is full do you want to compute now?\n");
        while(toupper(choice) != 'N' && toupper(choice) != 'Y') // The part where the program ask for Y or N.
        {
            choice = toupper(getch());
        }
        if(toupper(choice) == 'Y') // returns without changing the value of SIZE thus ending the while loop at main
        {
            return;
        }
        else if(toupper(choice) == 'N') // adds 10 to SIZE thus continuing the while loop in main and returns
        {
            printf("add another 10 answers\n");
            *SIZE += 10;
            realloc(answer, *SIZE);
        }
    }

    return;
}

Answer 1

可能还有其他问题（我不会仔细研究），但您肯定需要解决：

   while(item > 9 || item < 1)
    {
        scanf("%d", &item);
    }

如果 scanf 匹配零个项目，那么这是一个无限循环，scanf 重复返回 0，读取相同的数据并且不更改 item。您必须始终检查 scanf 返回的值。

Answer 2

这是一个严重的错误：

realloc(answer, *SIZE);

您没有保存返回值，因此您丢失了分配的内存。此外，您忘记了对象的大小。

原则上你应该这样做

Statistician tmp = realloc(answer, *SIZE * sizeof(int));
if (tmp == NULL)
{
    // Error handling
    // or just
    exit(1);
}
answer = tmp;

但是，这并不完全有帮助。问题是它只会改变函数内部answer 的值，而不会改变@987654324 的值@在main。为了更改arr 的值，您必须将arr 的地址传递给函数。类似于您对SIZE 所做的事情。顺便说一句：你为​​什么将counter 作为指针传递？您永远不会在函数中更改它，因此无需传递指针。

您当前的代码也没有初始化choice。

改变

    printf("Array is full do you want to compute now?\n");
    while(toupper(choice) != 'N' && toupper(choice) != 'Y') // The part where the program ask for Y or N.

到

    printf("Array is full do you want to compute now?\n");
    choice = ' ';
    while(toupper(choice) != 'N' && toupper(choice) != 'Y') // The part where the program ask for Y or N.

或更好：

    printf("Array is full do you want to compute now?\n");
    do
    {
        choice = toupper(getch());
    } while(toupper(choice) != 'N' && toupper(choice) != 'Y');

顺便说一句：

既然你有choice = toupper(getch());，你就不需要toupper(choice) != 'N'。只需choice != 'N'

说了这么多——你为什么要问函数内部这个问题？如果您在main 中执行，您的代码会简单得多。

类似：

int main(void) {

    int SIZE = 10;
    int c, count = 0, item = 0;
    int* arr;
    float mea, med;

    arr = calloc(10, sizeof(int));

    printf("Enter 10 answers\n");

    while(count < SIZE)
    {
        while(item > 9 || item < 1)
        {
            if (scanf("%d", &item) != 1) exit(1);
        }

        ++count;
        add(arr, count, item);
        item = 0;

        if (count == SIZE)
        {
            printf("Array is full do you want to compute now?\n");
            char choice;
            do
            {
                choice = toupper(getch());
            } while(choice != 'N' && choice != 'Y');

            if(choice == 'N')
            {
                printf("add another 10 answers\n");
                SIZE += 10;
                int* tmp = realloc(arr, SIZE * sizeof *arr);
                if (tmp == NULL) exit(1);  // or error handling
                arr = tmp;
            }
        }
    }
    system("cls");
    mea = mean(arr, count);
    med = median(arr, count);
    printf("mean = %f\n", mea);
    printf("median = %f\n", med);

    return 0;
}

void add(int* answer, int count, int item)
{

    int i, j, temp;
    bool swapped;

    
    answer[count - 1] = item;

    for(i = 0; i < count - 1; i++)
    {
      swapped = false;
      for(j = 0; j < count - i - 1; j++)
      {

        if(answer[j] > answer[j + 1])
        {
          temp = answer[j];
          answer[j] = answer[j + 1];
          answer[j + 1] = temp;
          swapped = true;
        }
      }

      if(swapped == false)
        break;
    }
    
    return;
}