释放具有结构节点的链表结构

Question

我有一个链表结构，里面有一个节点结构

struct gradeNode {
char courseName[sizeName];
int grade;
struct gradeNode *next;
struct gradeNode *prev;

struct gradeList {
struct gradeNode *head;
struct gradeNode *next;

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void destroyList(struct gradeList *head)
{
    struct gradeNode* tmp;

    while (head!= NULL)
    {
        tmp = head;
        head = head->next;

        free(tmp);
    }

    free(head);
}

这是主要内容

int i = 0;
for (i; i < numOfStuds; i++) {
    destroyList(&students[i].gradelist);
}

Answer 1

void destroyList(struct gradeList *head)
{
    struct gradeNode* tmp;

    while (head!= NULL)
    {
        tmp = head; //<<<<<<< assigning a struct gradeList* to a struct gradeNode*
        head = head->next;

        free(tmp); //<<<<<<< freeing the alias
    }

您正在将一种类型的指针分配给另一种类型的指针，然后释放它，这尤其有问题，因为 struct gradeList 似乎是 struct gradeNode 的成员。

检查你的警告。您没有收到 tmp = head 的警告吗？使用 gcc 7.2 我得到：

[x86-64 gcc 7.2 #1] warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]

https://godbolt.org/g/EWfLCn

释放具有结构节点的链表结构

free a struct of a linked list that have struct nodes

c

free

memory-management

linked-list