c++ - 指针未正确指向？

Question

我在一个线程中运行这段代码，假设 receivedPosts 和 td->window 是有效的:

std::vector<Post> *receivedPosts_n = new std::vector<Post>;
*receivedPosts_n = receivedPosts;

SendMessage(td->window, WM_TIMER, IDT_TIMER_FIND_NEW_POSTS_CALLBACK, 
    (LPARAM) receivedPosts_n);

我在 IDT_TIMER_FIND_NEW_POSTS_CALLBACK 运行这段代码(hwnd 是 td->window):

case IDT_TIMER_FIND_NEW_POSTS_CALLBACK:
    {
        std::vector<Post> *currentPosts_ptr = (std::vector<Post> *)lParam;

        //This vector turns up as undefined
        std::vector<Post> currentPosts = *currentPosts_ptr;
    }
    break;

但问题是 *currentPosts_ptr 变成了一个无效指针，即它指向随机内存。

指针有什么问题？

谢谢。

Answer 1

MSDN documentation表示对于 WM_TIMER 消息，lParam 的值是

A pointer to an application-defined callback function that was passed to the SetTimer function when the timer was installed.

如果您需要发送自定义消息，最好只使用 WM_USER through 0x7FFF专门为这种情况设计的。