如何通过PostMessage发送字符串？

发布于 2024-08-02 13:36:47 字数 547 浏览 10 评论 0原文

在我的应用程序中，我想从不同的线程向对话框发送消息。我想将 std::exception 派生类引用传递给对话框。

像这样的事情：

try {
       //do stuff
}
catch (MyException& the_exception) {
    PostMessage(MyhWnd, CWM_SOME_ERROR, 0, 0); //send the_exception or the_exception.error_string() here
}

the_exception.error_string() 的 the_exception.error_string() 中的错误

LPARAM CMyDlg::SomeError(WPARAM, LPARAM)
{
    show_error( ?????
    return 0;
}

我想在对话框中接收消息并显示传递 std::string 我想使用 PostMessage 也可以。

原文

Inside my app, I want to send a message to a dialog from a different thread.
I want to pass an std::exception derived class reference to the dialog.

Something like this:

try {
       //do stuff
}
catch (MyException& the_exception) {
    PostMessage(MyhWnd, CWM_SOME_ERROR, 0, 0); //send the_exception or the_exception.error_string() here
}

I want to receive the message in my dialog and show the error that is in the_exception.error_string()

LPARAM CMyDlg::SomeError(WPARAM, LPARAM)
{
    show_error( ?????
    return 0;
}

passing the std::string the_exception.error_string() using PostMessage would also be ok, I guess.

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还在原地等你 2024-08-09 13:36:47

您无法在 PostMessage 中传递字符串的地址，因为该字符串可能是堆栈上的线程本地的。当另一个线程拾取它时，它可能已经被销毁了。

相反，您应该通过 new 创建一个新的字符串或异常对象，并将其地址传递给另一个线程（通过 PostMessage 中的 WPARAM 或 LPARAM 参数）。然后另一个线程拥有该对象并负责销毁它。

以下是一些示例代码，展示了如何完成此操作：

try
{
    // do stuff
}
catch (const MyException& the_exception)
{
    PostMessage(myhWnd, CWM_SOME_ERROR, 0, new std::string(the_exception.error_string));
}


LPARAM CMyDlg::SomeError(WPARAM, LPARAM lParam)
{
    // Wrap in a unique_ptr so it is automatically destroyed.
    std::unique_ptr<std::string> msg = reinterpret_cast<std::string*>(lParam);

    // Do stuff with message

    return 0;
}

You can't pass the address of the string in PostMessage, since the string is probably thread-local on the stack. By the time the other thread picks it up, it could have been destroyed.

Instead, you should create a new string or exception object via new and pass its address to the other thread (via the WPARAM or LPARAM parameter in PostMessage.) The other thread then owns the object and is responsible for destroying it.

Here is some sample code that shows how this could be done:

try
{
    // do stuff
}
catch (const MyException& the_exception)
{
    PostMessage(myhWnd, CWM_SOME_ERROR, 0, new std::string(the_exception.error_string));
}


LPARAM CMyDlg::SomeError(WPARAM, LPARAM lParam)
{
    // Wrap in a unique_ptr so it is automatically destroyed.
    std::unique_ptr<std::string> msg = reinterpret_cast<std::string*>(lParam);

    // Do stuff with message

    return 0;
}

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