Creating A D DLL For Use By VB

[Derek Parnell]

On Sun, 19 Mar 2006 00:51:15 +0000 (UTC), strkweatherr at mchsi.com wrote:

> I'm having the same problem with DigitalMars D as I had with DigitalMars C/C++,
> but nobody over there has answered any of my questions. 
> 
> I started with the MyDLL package and modified it so that it accepts two ints and
> returns the sum. Test.exe works fine, but VB says the .lib file doesn't exist. I
> am assuming that is because it isn't in a recognizable format.

> ...

> Does anyone have a piece of source code, that works, for a DLL that is
> accessible from non-D programs and that is less than 50 lines long?

I just had a go now, following the instructions in the DigitalMars docs.
First I took the 'mydll' source in the docs and saved it to a file called
'mydll.d'. Then I created a new file called 'testdll.d' and here is its
source ...

--------testdll.d-----------
import mydll;
import std.math;

extern (Windows)
{
 int sqrab(short a, short b)
 {
    // Calculates the square root of the sum of two squares.
    // (eg. used to find the length of the hypotenuse)

    return cast(int)sqrt((cast(real)a * cast(real)a) + (cast(real)b *
cast(real)b));
 }
}

--------------

I then created a .DEF file which contained ...

-------------testdll.def----------------
LIBRARY         TESTDLL
DESCRIPTION     'My test DLL written in D'

EXETYPE         NT
CODE            PRELOAD DISCARDABLE
DATA            PRELOAD SINGLE

EXPORTS
sqrab       @2
------------------------------------------

I next compiled it with the following command line ...

   dmd -oftestdll.dll mydll.d testdll.d testdll.def

Then moved the testdll.dll file to the windows system32 folder,

Finally I created a VB module that contained the line ...

  Public Declare Function sqrab Lib "testdll" _
         (ByVal A As Integer, ByVal B As Integer) As Long

and the VB form used the DLL command as ...

   Sub Form_Click()
      Dim x As Integer
      Dim y As Integer

      x = CInt(Text1.Text)
      y = CInt(Text2.Text)

      result = sqrab(x, y)

      Label1.Caption = CStr(result)
      Label2.Caption = CStr(Sqr(CLng(x) * CLng(x) + CLng(y) * CLng(y)))
   End Sub 

And it all just worked.
-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocracy!"
20/03/2006 6:04:50 PM