You need to compile the dll with the __pascal calling convention, mark the relevant functions as exported, compile your dll, and then create a type library using the Microsoft IDL compiler (MIDL) to describe the functions. Once the type library is registered on a target machine, you should be able to put your dll in the system32 directory and make function calls into it from a VB program.

ld

__declspec(dllexport) marks your function as exported.

Compiling with __pascal is set in the compilation options on the Project Settings dialog, C/C++ tab. Select "Code Generation" in the dropdown (this is for VC++ 6.0, btw, it''s in the list somewhere in VC++.NET), and change the calling convention to __stdcall (the pascal calling convention renamed, basically).

Creating a type library is a process you will have to learn on your own. Here are the keywords: MIDL, IDL, ODL, "Interface Definition Language", "Object Definition language". There is enough on MSDN to get going, although I wouldn''t exactly call it good material. Registering the dll won''t be possible unless you link the type information directly into the dll, a process I have no experience with. Instead, create the type library and register it on your machine using regtlib.exe, then drop the dll into %WINDOWS%\system32.

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quote:Original post by huahsin68

From my VC++ program:

extern "C" int _declspec(dllexport) __stdcall Mymulti (int& a, int& b)
{
return a*b;
}

From my VB program:

Private Declare Function xxx Lib "dll.dll" Alias "_Myadd@8 " (ByRef a As Long, ByRef b As Long) As Long

5:05:06 AM]

This could be the problem, but then again you could be posting just as an example.

There''s (possibly) another problem here. The type int& is a reference to an int (this is a C++ thing, not a C thing) This could be confusing the compiler. Try using (since you are not changing the values a and b) int a, int b in the C function above, and change the Byref''s to ByVals ....