Re: Accessing DLL

Question

Sivaram,
You will need to get the DLL into a LIB and wrapper it. Do this (in Win
3.1 & Borland) using the IMPLIB command. Then you can wrapper the lib.
Obviously, you will need to know the function prototype in order to wrapper.
The most common problem is that the functions will probably be defined
as using the PASCAL calling convention and Forte generates function
prototype without the PASCAL. If that happens, you need to modify the
generated *.cc files to add before compiling and linking.
Regards,
Tony Elmore
MSF&W
Springfield, IL
[email protected]
-----Original Message-----
From: Sivaram S Ghorakavi <[email protected]>
To: 'forte' <[email protected]>
Date: Monday, October 27, 1997 11:26 AM
Subject: Accessing DLL
Hello Guys,
Can anybody tell me is there any way to access DLLs from Forte ??
Through external system wrapping or Direct accessing!!!
Any clue will be very helpful
Thanx
Sivaram
International Business Corporation (IBC)

Answer 1

Pascal calling convention is implemented in R3.
Please review technote 11183 to set it up.
linh ...
At 03:15 PM 10/29/97 -0600, Jeanne Hesler wrote:
Hi Stephen,
If your errors show all of your function statements with an underscore at
the beginning, then that function has most likely been defined using the
pascal calling convention. Unfortunately, Forte does not provide a way for
you to specify the pascal calling convention prior to generating its
wrapper code. This makes it a bit awkward to wrapper functions that use
that convention, since you must do the fcompile manually. After you make
the library distribution, but before you do the fcompile, you will need to
edit the *.cc files that were generated, and add the call convention on
each of your function statements. This is a bit ugly, especially if you
have 200+ function statements, but once you have everything wrappered,
hopefully you will not need to do it again for a while.
As a point of interest, using the underscore to decorate the function name
for the pascal call convention is not specific to the Microsoft compilers.
Call conventions specify what sequence is used to pass the parameters from
the caller to the callee, and whether the caller or the callee will reset
the stack upon return from the function call. It is imperative that both
caller and callee follow the same rules, or the results will be fairly
disastrous. Using the underscore to decorate the name helps prevent that
kind of mismatch by keeping them from linking accidentally.
On the other hand, you probably can blame Microsoft for the prevalence of
the pascal call convention. Even though cdecl is the default call
convention for the compiler, it is fairly common for developers in the
Windows realm to use the pascal convention instead. This is the convention
used by all of the Windows API's, and I think people just got used to
specifying them that way. In fact, the convention is so prevalent that
some development environments will only utilize external DLL's where the
call convention is pascal. This makes it a bit of a challenge for those of
us who are producing external DLL's to be used in more than one development
environment. When we created the Forte version of our Imaging Developer
product, we changed the call conventions to simplify the wrappering
process, but I suspect that most vendors will stick with the pascal
convention in their DLL's.
Jeanne--
Pardon me for butting in.
I am following this conversation with great interest
because I am trying to do the same thing and I lack
experience in working with the Microsoft build environment.
I have from vendor X the following: A.dll B.dll C.dll and
A.lib and block of about 200 Declare Function statements
all of which reference library A.dll.
So far our attempts to fcompile a Forte 3E0 wrapper have
failed to link due to unresolved symbols, specifically the
Forte wrapper calls, each prefixed in the linker error mssg
with "_". I have heard that the "_" prefix is a Microsoft
"decoration code" for something.
I've done TOOL wrappers for ANSI C callouts on UNIX but this
DLL stuff looks like it has more moving parts.
Are there any tools in the MSVC 5 environment that would
enable us to see the service interfaces that the DLL's
export or determine what is in the LIB?
Stephen Porterfield
Developer
[email protected]
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