Re: transmit some values from one thread to another thread

From:
"ScottMcP [MVP]" <scottmcp@mvps.org>
Newsgroups:
microsoft.public.vc.mfc
Date:
Sun, 31 Oct 2010 14:58:22 -0700 (PDT)
Message-ID:
<a07a95db-e6f5-4eef-9792-358dfc062469@u17g2000yqi.googlegroups.com>
On Oct 31, 4:09 pm, mfc <mfcp...@googlemail.com> wrote:

Or with the std:map:
//where mymap will contain all information from all serialports:
std::map <CString, CString>mymap;
wnd->PostMessage(UWM_TX_TO_DOC, mymap);


You can't do it that way. mymap will not fit into the pointer-sized
message parameter, and as a stack variable it is likely to be
destroyed before the receiving thread gets it.

Allocate with 'new' and use 'delete' in the message handler. The
thread that does the 'new' may not use the structure after it has been
passed in PostMessage.

CString * pParameter = new CString(...); // Doesn't have to be
CString. Any object type can be used.
wnd->PostMessage(UWM..., (WPARAM)pParameter, 0);

There is no reason to send several PostMessages for just one port.
You can send information of any desired size and any desired structure
with one PostMessage call. Send the address of the structure(s) in
the wParam and/or lParam parameters. But do NOT send the address of a
stack variable!

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