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VRf: VEE function overlays

Question asked by VRFuser on Jan 28, 1998
I am working on software for test set about 2000 miles away, which makes
the testing of the software rather challenging.  Much of it uses the
PeekPoke DLL, and requires specific responses to continue.  In order to
test the software, we need to put temporary patches in several functions of
a large library.  The challenge is to assure that the patches don't end up
in the final code.  The following technique was very useful for this and
I'd like to pass it along.

When VEE loads functions from a library and calls them without the prefix
of "mylibrary.", VEE will use the function that was loaded first.  This
means that you can create a library of certain functions that are the same
name as the ones another library.  These "overlay functions" are only
active when you load that library first, otherwise the originals take
precedence.

Original Library        Available functions for Debug
Function1 ------------- Function1
Function2 --X       --- Function2
                   / -- MonitorPnl
Overlay Library   / /
Function2 -------- /
MonitorPnl --------

I created a library called "Not_Live" with the patched functions.  In
addition to simulating the expected responses, they call to a Monitor Panel
that shows what is going on.  The original libraries are unmodified, which
means I don't have to re-certify them.

The following information applies to VEE 3.12.  Would this work on VEE
4.01?

Jim Kneale               kneale.j.b@postal.essd.northgrum.com
ph  (410)765-3807   ///  Northrop Grumman ESSD
fax (410)993-8126  (..)  Baltimore MD USA
----------------ooO-()-Ooo------------------
#include "std_disclaimer.h" //opinions are my own

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