c - c 中的致命堆损坏错误。无法处理，我需要建议

Question

我编写了一个使用结构和动态内存分配的程序。我希望获得帮助来理解为什么如果我按 4(这意味着退出菜单)我会收到错误:

HEAP CORRUPTION DETECTED: after Normal block (#76) at 0x00845EE8.

它链接到函数deletelist()。我真的不明白为什么会发生以及如何解决这个问题。

这是代码:

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

#define PRO_OP 1
#define CON_OP 2
#define PRINT_OP 3
#define EXIT_OP 4

#define STR_LEN 50
#define MAX_LIST_LENGTH 10

typedef struct reasonList
{
    char* listName;
    char* reasons[MAX_LIST_LENGTH];
    int numReasons;
} reasonList;


void initList(reasonList* list, char* name);
void addReason(reasonList* list);
void printList(reasonList list);
int menu(void);
void myFgets(char str[], int n);
void deleteList(reasonList* list);

int main(void)
{
    char dilemma[STR_LEN] = { 0 };
    int op = 0;

    reasonList proList;
    initList(&proList, "PRO");
    reasonList conList;
    initList(&conList, "CON");

    printf("What is your dilemma?\n");
    myFgets(dilemma, STR_LEN);

    while (op != EXIT_OP)
    {
        op = menu();

        switch (op)
        {
        case(PRO_OP):
            addReason(&proList);
            break;
        case(CON_OP):
            addReason(&conList);
            break;
        case(PRINT_OP):
            printf("Your dilemma:\n");
            printf("%s\n\n", dilemma);

            printList(proList);
            printList(conList);
            break;
        case(EXIT_OP):
            deleteList(&proList);
            deleteList(&conList);
            break;
        }
    }
    printf("Good luck!\n");
    getchar();
    return 0;
}

/*
Function will initialize a reason list
input: the list to init, and its name
output: none
*/

void initList(reasonList* list, char* listName)
{
    list->listName = (char*) malloc(sizeof(char));
    strcpy(list->listName, listName);//equal to PRO or CON
    for (int i = 0; i < MAX_LIST_LENGTH; i++)
    {
        list->reasons[i] = (char*)malloc(sizeof(char) * STR_LEN);
        if (list->reasons[i] == NULL)
        {
            printf("no memmory left\n");
            exit(1);
        }
        strcpy(list->reasons[i], "");
    }
    list->numReasons = 0;
}

/*
Function will add a reason to the list
input: the list to add to and its name
output: none
*/
//
void addReason(reasonList* list)
{
    char* newReason = (char*)malloc(sizeof(char) * STR_LEN);
    printf("Enter a reason to add to the list %s:\n", list->listName);
    myFgets(newReason, STR_LEN);

    if (list->numReasons >= MAX_LIST_LENGTH)//if no memory left
    {
        //free(newReason);
        return;
    }
    free(list->reasons[list->numReasons]);
    list->reasons[list->numReasons] = newReason;
    list->numReasons++;
    list->reasons[list->numReasons] = NULL;
}


/*
Function will print a list of reasons
input: the list
output: none
*/
void printList(reasonList list)
{
    printf("list %s\n--------\n", list.listName);
    for (int i = 0; i < list.numReasons; i++)
    {
            printf("%s", list.reasons[i]);
        printf("\n");
    }
    printf("\n");
}

/*
Function shows menu and returns user's choice
input: none
output: user's choice
*/
int menu(void)
{
    int op = 0;
    printf("Choose option:\n");
    printf("%d - Add PRO reason\n", PRO_OP);
    printf("%d - Add CON reason\n", CON_OP);
    printf("%d - Print reasons\n", PRINT_OP);
    printf("%d - Exit\n", EXIT_OP);
    scanf("%d", &op);
    while (op < PRO_OP || op > EXIT_OP)
    {
        printf("Invalid option. Try again: ");
        scanf("%d", &op);
    }
    getchar(); // clean buffer
    return op;
}

/*
Function will delete a list
input: the list to delete
output: none
*/
void deleteList(reasonList* list)
{
    for (int i = 0; i < list->numReasons; i++)
    {
        free(list->reasons[i]);
        list->reasons[i] = NULL; // set pointer to NULL
    }
    free(list->listName);
    list->listName = NULL; // set pointer to NULL
}


/*
Function will perform the fgets command and also remove the newline
that might be at the end of the string - a known issue with fgets.
input: the buffer to read into, the number of chars to read
*/
void myFgets(char str[], int n)
{
    fgets(str, n, stdin);
    str[strcspn(str, "\n")] = 0;
}

Answer 1

我无法重现段错误，但 valgrind 提示 initList() :malloc(sizeof(char))当您需要 \0 时，它会分配 1 个字节(strlen(listName) + 1 表示空字符串) .

无关，为了消除内存泄漏，请观察您在 initList() 中的情况为 MAX_LIST_LENGTH 分配空间reasons但在 deleteList()你只有自由list->numReasons 。建议您将其保留为 addReasons()分配空间:

void initList(reasonList* list, char* listName) {
    list->listName = malloc(strlen(listName) + 1);
    strcpy(list->listName, listName);
    list->numReasons = 0;
}

void addReason(reasonList* list) {
    if (list->numReasons >= MAX_LIST_LENGTH)
        return;
    list->reasons[list->numReasons] = malloc(STR_LEN);
    printf("Enter a reason to add to the list %s:\n", list->listName);
    myFgets(list->reasons[list->numReasons++], STR_LEN);
}

如果您希望能够删除(并重复使用)reasons[i]然后在 initList()你想初始化list->reasons[i] = NULL我建议(为了对称)创建一个 deleteReason()然后您可以在 deleteList() 中使用该函数.

另一个有效的设计(因为你的 reasons 是固定大小的)是分配所有 reasons在initList() (就像你一样)。在 addReaon()重用分配的字符串(没有 malloc() 或 free() )。在 deleteList()全部免费MAX_LIST_LENGTH原因。

最好检查 malloc() 的返回值.

不要转换 void *来自malloc() .

更喜欢将与类型相反的变量传递给 sizeof 。在上面代替 sizeof(char)使用sizeof *list->listName或 sizeof *listName ; that said 大小(字符)is defined as 1` 所以我总是忽略它。