From: stidolph@magnet.com
Subject: Re: [delphi] How do I prevent multiple instances of DLL objects?
Date: Tue, 25 Jul 1995 08:39:58 -0400

In Windows 3.1 (or NT/95 16 bit subsystems) DLL's are only loaded once. The
first time a DLL is loaded the routine LibMain (if there) is called passing
in the HINSTANCE handle for the DLL and some other info.  Your DLL will have
its own data segment (DS register), but will use the stack of the calling
application.  When I was writing DLL's for WinHelp I would make a structure
that would keep track of all information for a given task and store it in a
table with one of the data elements a task handle.  When a routine in my dll
was called I would call GetCurrentTask and walk through the table looking
for the matching task handle.  If the task didn't exist I would add a new entry.

Generally I would suggest that you have an initialization routine that
should be called by all programs using the dll to register whatever
application information you need.  Also have a routine that will be called
on application termination to free memory allocated for that application.

Your WEP routine should delete any memory not already freed.  Good Luck!

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David Stidolph               stidolph@magnet.com

Why is it that we drive on a parkway and park on
a driveway?
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