🚀 go-pugleaf

a09748@giant.mindlink.bc.ca (ESSA) wrote:

>
>Having a frustrating time trying to call a function in a DLL developed in
>VC++ 4.0 from Visual Basic 4.0 (32bit). I'm getting VB error 49 (bad DLL
>calling convention) from the following simple function ...
>
>In mydll.h
>#define DllExport __declspec(dllexport)
>extern "C" long DllExport TestLongParam(long lParam);
>
>In mydll.cpp
>extern "C" long DllExport TestLongParam(long lParam)
>{
>	TRACE("TestLongParam called with %ld\n", lParam);
>	return(1L);
>}
>
>The Declare in VB is
>Declare Function TestLongParam Lib "MYDLL.DLL" (ByVal lParam As Long) As Long
>
>When I call TestLongParam from VB, I get the TRACE output with the correct 
>value for the passed parameter, but on return, VB gives error 49.
>
>Can anyone sugesst what is wrong with the way I have declared the functions ?
>I have played around with the __stdcall modifier, the WINAPI macro and even
>tried the old obsolete FAR PASCAL with no success.
>
>

I may have a clue since I had a similar situation today.
If a DLL is compiled with VB 4.0 WITHOUT a module definition file and
uses  the new __declspec( dllexport ) to declare functions as
exportable, VB4 cannot seem to understand them. At least that is what
I discovered today on my own.

I created a small DLL with a function that passes a long value and
returned the long value. For example:

#define DllExport	__declspec( dllexport )

DllExport DWORD		Test( DWORD data );

DWORD
Test( DWORD data )
{
	return data;
}

VB4 could not seem to handle this. Yet, if I went back to the
traditional method (FAR PASCAL), used a module definition file and
declared the function name in the EXPORTS section, I had no problem. I
really don't know enough about VB4 or the __declspec( dllexport ) to
know why this is...but as soon as I used an EXPORTS section and a
module definition file, all my problems went away.

I hope this helps. I know it's a stab in the dark but it sure did
cause me grief and sounded close to the problem you have encountered.

Good luck,

Bill Boland
--------
billbo@ix.netcom.com
Just a friendly little hobbit. Master of his domain.