Hi,

I use VC++'s Win32 DLL Wizard to create a DLL with these things:

// IN .CPP
int (*f1)(int);
LIBRARY_API int Start(int (*f)(int))
{
    f1 = f;

// IN .H
#ifdef LIBRARY_EXPORTS
#define LIBRARY_API __declspec(dllexport)
#else
#define LIBRARY_API __declspec(dllimport)
#endif
LIBRARY_API int Start(int (*f)(int));

Then In VB, I write

Declare Function MyStart Lib "e:\my waste\library\debug\library.dll" Alias
"Start" _
    (ByVal p As Long) As Long

Function MyProc(ByVal x As Long) As Long
...
End Function

and I call
x = MyStart (AddressOf MyProc)

Then VB says it cannot find the entry point. I try adding a DEF file to the
VC project, this time, VB says the calling convention is bad. What should I
do? Furturemore, since Win32 DLL wizard didn't create a DEF file for me, is
it really unnecessary?

--
Wang Weijun
wangwj at taslon dot com | wangwj at iname dot com

VB uses __stdcall calling convention only.

This is pointing to a default calling convention function (__cdecl).
The pointer you are assigning to it is a VB function, therefore
__stdcall.

Change the declaration to:
   LIBRARY_API int (*f1)(int);

Then change
    #define LIBRARY_API __declspec(dllimport)

to
    #define LIBRARY_API __declspec(dllimport) __stdcall

(I think that's right; I still use DEF files to avoid name
mangling)

<snip>

Right. The names are mangled. You have to either use
a DEF file or reference the decorated name in the Alias
clause of your function declaration in VB. Either way
works fine.

Because it is. If you use the DEF file to avoid the name,
change LIBRARY_API to just __stdcall.  You really only
want to use either __declespec( dllimport | dllexport )
or the DEF file, not both.

But for interaction with VB, __stdcall is mandatory.

It's unnecessary unless you need to change the default behavior
of the compiler (like name decoration).

Thank you, Ron

It works fine now (in VB and VC). I simply assign all function I use to
__stdcall in the DLL and keep the DEF file.

--
Wang Weijun
wangwj at taslon dot com | wangwj at iname dot com