Eg:

HWND h = pSomeDialog->SendMessage(MSG, w, l);
...

In the message handler:

// do whatever is needed with `w` and `l`.
// in my case `w` is size of buffer
// in my case `l` is the actual buffer to receive text.

// but I also want to return the handle to a popup window:
return m_popup.GetSafeHWnd():

Is this considered safe? Or should I add a custom message specifically for getting the handle via the w parameter?