BUG: DdeConnect Never Returns
Article ID: 136218
Article Last Modified on 11/21/2006
APPLIES TO
- Microsoft Win32 Application Programming Interface, when used with:
- Microsoft Windows NT Server 3.51
- Microsoft Windows NT Workstation 3.51
This article was previously published under Q136218
SYMPTOMS
A 32-bit application calls DdeConnect when all previous DDEML
initialization has been performed. DdeConnect never returns.
CAUSE
Any thread that creates a top-level window and doesn't have a message
loop will cause DdeConnect to block. This is because DdeConnect calls
SendMessage(HWND_BROADCAST...). In this call, SendMessage will put the
message in the target thread's message queue and block the calling
thread. If the target thread doesn't have a message loop, it will never
process this message and therefore never return.
One complication is that some things create windows without the knowledge
of the calling thread. It is known that some SQL, RPC, and DDEML function
calls will do this. Any top-level window that is created by a thread that
has no message loop will cause this to happen.
RESOLUTION
The only current solution is to add a message loop to the thread that
created the window.
STATUS
Microsoft has confirmed this to be a problem in the Microsoft products
listed at the beginning of this article.
Additional query words: 4.00
Keywords: kbbug KB136218