call sub

[Claudia Dell'Era]

Hi!
I wrote the code I pasted at the end of the mail to call a
sub from a dll file. Apparently the code looks correct to
me but instead of returning the correct value of z it
gives me only zeros. Does someone of you see any mistake
for example in the use of the call sub? Thank you
Here is the code:

Declare Sub asum Lib "D:\Dll\arr\koedll.dll" (x As Double,
y As Double, z As Double, n As Integer)
Sub koelarr()
'
' koelarr Macro
' Macro written 10/3/2003 by Claudia Dell'Era Try to link
an array
'

'
Dim x() As Double, y() As Double, z() As Double
Dim n As Integer, i As Integer

Worksheets("Sheet2").Activate
n = Cells(2, 4)

ReDim x(1 To n) As Double, y(1 To n) As Double, z(1 To
n) As Double

Worksheets("Sheet2").Activate
For i = 1 To n
x(i) = Cells(i + 1, 1)
Next i

For i = 1 To n
y(i) = Cells(i + 1, 2)
Next i

Call asum(x(1), y(1), z(1), n)

For i = 1 To n
Cells(i + 1, 3) = z(i)
Next i

End Sub

 

[Chip Pearson]

Claudia,

Your code looks good to me, and a quick test with a DLL written in C++ bears
this out. How is your 'asum' function declared in the DLL? Remember an
integer in C is a Long in VBA.

 

[Claudia Dell'Era]

Hi Chip
Thanx for your answer. "asum" is a simple function
(x+y=z) I made to check if the "array passing" from the
dll to VBA works.The real program I have to use in
practice is much bigger but if already doesn't work with
this... The dll is written in Visual Fortran. I paste the
code since it is short. Thank you

! koedll.f90
!
! FUNCTIONS/SUBROUTINES exported from koedll.dll:
! koedll - subroutine
!
subroutine asum(x, y, z, n)

implicit double precision (a-h,o-z)
dimension x(n), y(n), z(n)

! Expose subroutine koedll to users of this DLL
!
!DEC$ ATTRIBUTES DLLEXPORT::asum
!DEC$ ATTRIBUTES ALIAS : "asum" :: asum

! Variables

! Body of koedll

do i = 1, n
z(i) = y(i) + x(i)
end do
return
end subroutine

 

[Chip Pearson]

Claudia,

I don't know Fortran, so I have no idea whether your Fortran code is correct
or not. Is the Fortran function expecting the variables to be passed "by
reference" (i.e., pointers) or "by value" (i.e., actual values)?