Question

我的理解是，对于每一个malloc，我们应该在退出之前自由。根据valgrind报告，我没有泄漏。也就是说，valgrind报告此代码有错误：Address 0x402613c is 4 bytes inside a block of size 8 free'd

为简洁起见，下面只是链接列表代码部分的剪辑，显示节点类型和我malloc或释放节点的代码段。

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;
        }
    }
}

Answer 1

错误告诉您在释放内存后使用指向释放内存的指针：

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.

而且，实际上看着你的代码，它几乎和上面的例子一样明显（正如BLUEPIXY在comment中指出的那样）：

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

修正：

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

Valgrind错误但没有泄漏

1 个答案: