有一个致命的错误代码 - 损坏的堆

Question

来自外部编译器的新图片..退出代码正常吗？

enter image description here

这是完整的代码。在将想要的输出打印到屏幕后，我遇到了一个故障程序。我想这是我为结构数组分配内存的方式以及 for 循环中每个结构的 .name 字段的问题。

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

#define MAX_NAME_LEN 50

typedef struct stud
{
char *name;
int marks[4];
float avg;
}student;


student* Create_Class(int);
void Avg_Mark(student*);
void Print_One(student*);
void printExcellent(student*);

void main()
{
int size, i;
student *arr, *newArr;
printf("\nEnter the number of students: ");
scanf_s("%d", &size);
newArr = Create_Class(&size);
for (i = 0; i < size; i++)
{
    printExcellent(newArr+i);
}
for (i=0;i<size;i++) free(newArr[i].name);
free(newArr);
_getch();
}

student* Create_Class(int size)
{
student *p;
char str[MAX_NAME_LEN];
int i, j;
p = (student*)calloc(size , sizeof(student));
if (!p)
{
    printf("Memory allocation failure.");
    exit(1);
}

for (i = 0; i < size; i++)
{
    printf("Enter your name: ");
    rewind(stdin);
    gets(str);
    p[i].name = (char*)calloc(strlen(str)+1,sizeof(char));
    if (!(p[i].name))
    {
        printf("Memory allocation error!");
        exit(1);
    }
    strcpy_s(p[i].name,50,str);
    printf("Enter your marks: ");
    for (j = 0; j < 4; j++)
    {
        scanf_s("%d", &p[i].marks[j]);
    }
    Avg_Mark(p + i);
}
return p;
}


void Avg_Mark(student* s)
{
int i, sum=0;
for (i = 0; i < 4; i++)
    sum += s->marks[i];
s->avg = (float)sum / 4;
}


void Print_One(student* s)
{
printf("The average of %s is %.1f\n", s->name, s->avg);
}

void printExcellent(student* s)
{
if ((s->avg) > 85)
    Print_One(s);
}

Answer 1

我会为你指出我看到的所有可疑之处：

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

#define MAX_NAME_LEN 50

typedef struct stud
{
    char *name;
    int marks[4];
    float avg;
}student;


student* Create_Class(int);
void Avg_Mark(student*);
void Print_One(student*);
void printExcellent(student*);

void main()
{
    int size, i;
    student *arr, *newArr;
    printf("\nEnter the number of students: ");
    scanf_s("%d", &size);

    // This is wrong. Remove the &...
    newArr = Create_Class(&size);

    for (i = 0; i < size; i++)
    {
        printExcellent(newArr+i);
    }
    for (i=0;i<size;i++) free(newArr[i].name);
    free(newArr);
    _getch();
}

student* Create_Class(int size)
{
    student *p;
    char str[MAX_NAME_LEN];
    int i, j;

    // Consider checking size for a sane value.

    // Ok, allocate an array of students.
    p = (student*)calloc(size , sizeof(student));
    if (!p)
    {
        printf("Memory allocation failure.");
        exit(1);
    }

    for (i = 0; i < size; i++)
    {
        printf("Enter your name: ");

        // These 2 lines scare the heck out of me.  I'd really do this differently.
        // gets is the devil and the see:
        // https://stackoverflow.com/questions/20052657/reversing-stdin-in-c
        // for why this may not work well.

        rewind(stdin);
        gets(str);

        // What if str is not a terminated string?  Then 1 char of 0?  Guess this is ok.  Hope it doesn't overflow on the copy below though (consider fixed max size and not using a temporary)
        p[i].name = (char*)calloc(strlen(str)+1,sizeof(char));
        if (!(p[i].name))
        {
            printf("Memory allocation error!");
            exit(1);
        }
        // Do a fast copy of up to 50 chars. I'd really want to verify this output to be sure it works. 
        strcpy_s(p[i].name,50,str);
        printf("Enter your marks: ");
        for (j = 0; j < 4; j++)
        {
            // Hope this inputs the way you want.
            scanf_s("%d", &p[i].marks[j]);
        }

        // This should work, but I prefer more explicit pointers.
        Avg_Mark(p + i);
    }

    return p;
}


void Avg_Mark(student* s)
{
    // What if s is Null?

    int i, sum=0;

    // 4 is a magic number.  Make this a constant.
    for (i = 0; i < 4; i++)
        sum += s->marks[i];

    // This won't be as accurate as you want.  Consider an integer solution.
    s->avg = (float)sum / 4;
}


void Print_One(student* s)
{
    // What if s is Null?  What about s->name?
    printf("The average of %s is %.1f\n", s->name, s->avg);
}

void printExcellent(student* s)
{
    // What if s is Null?
    if ((s->avg) > 85)
        Print_One(s);
}

注意：在浏览这段代码时，我没有看到任何“危险信号”，除了大小上的 & 可能还有获取/倒带调用。我仍然会向您的函数添加空断言，并使用调试器对其进行检查，以确保一切都如您所愿。老实说，这里发生了很多事情，我更喜欢调试器的帮助，而不是我在编写 cmets 时快速跟踪代码。

---

更新

如果我将您的所有 scanf_s 调用更改为 scanf() 调用，请将您的 gets() / rewind() 调用替换为简单的 scanf("%s", str) 调用，并将您时髦的 strcpy_s() 函数更改为更简单的 strcpy() 或 strncpy() 调用，你的程序对我来说似乎没有崩溃。我的钱是strcpy_s() 调用在进行“快速”复制时会损坏 RAM。