c - Valgrind错误，但无泄漏

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Closed 5 years ago.

C Linked List valgrind Invalid Read of Size
（1个答案）
我的理解是，每一个Maloc我们在离开之前都应该自由。根据valgrind的报告，我没有泄密。也就是说，valgrind报告这个代码有一个错误：Address 0x402613c is 4 bytes inside a block of size 8 free'd
为了简洁起见，下面只是链接列表代码的一部分片段，它显示了节点类型和我malloc或释放节点的代码部分。

typedef struct node
{
    int n;
    struct node* next;
}
node;

// global variable for the head of the list
node* head = NULL;

int main(void)
{
    // user menu
    while (true)
    {
        printf("Please choose an option (0, 1, 2): ");
        int option = GetInt();

        switch (option)
        {
            // quit
            case 0:
                free_nodes(head);
                printf("Goodbye!\n");
                return 0;

// snipped: code that calls insert and print functions

bool insert_node(int value)
{
    // create new node
    node* new_node = malloc(sizeof(node));
    if (new_node == NULL)
    {
        return false;
    }

    // snipped: some code that adds nodes to linked list
 }

/**
 * Frees all of the nodes in a list upon exiting the program.
 */
void free_nodes(node* list)
{
    // initialize pointer
    node* curr_node = head;

    // initialize variable for end of list
    bool is_end = false;

    // free nodes
    while (!is_end)
    {
        // if an empty list, free node and exit
        if (curr_node->next == NULL)
        {
            free(curr_node);
            is_end = true;
        }
        // else free node list until end of list if found
        else
        {
            free(curr_node);
            curr_node = curr_node->next;
        }
    }
}

最佳答案

错误是告诉您在释放内存后正在使用指向已释放内存的指针：

void *m = malloc(8);
char *s = m + 4;
free(m);
*s = 29;    // This would generate that warning.
int c = *s; // This would also generate that warning.

实际上，看看你的代码，它几乎和上面的例子一样明目张胆（正如BLUEPIXY在他的comment中指出的那样）：

free(curr_node);
curr_node = curr_node->next;

修复：

node *next = curr_node->next;
free(curr_node);
curr_node = next;

关于c - Valgrind错误，但无泄漏，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24275939/