Calling a Fortran dll with more than one array

[esben_auken]

Hi,

Can anyone direct me to an example where a subroutine in a Fortran dll is called with more than one array? I am calling form Delphi but a C example is as good.

I do not have problems passing a mixture of integers, reals and one array. When I try to pass two arrays I get an acces violation when I try to address array number two in the Fortran dll.

[Steven_L_Intel1]

What's the datatype of the array? Show us your Delphi and Fortran declarations of the routine. Unless you're passing character arrays, I can't think of a reason passing multiple arrays would be an issue.

[esben_auken]

Thanks.

Here is the Delphi code:

var
 Form1: TForm1;
 procedure TestArray(Length: integer; AInteger: array of integer; RReal: Array of double); stdcall; external 'testdll.dll';

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
 I        : integer;
 AInteger : array of integer;
 AReal : array of double;
 Length : integer;
begin

  //Transfer of integer and real arrays
 Length:=4;
 setlength(AInteger,Length);
 setlength(AReal,Length);
 for I:=0 to Length-1 do AInteger:=I;
 for I:=0 to Length-1 do AReal:=I*3/2;

 TestArray(Length,AInteger,AReal)
end;

And here is the fortran code

subroutine TestArray(Length, AInteger,AReal)
!DEC$ ATTRIBUTES DLLEXPORT :: TestArray
!DEC$ ATTRIBUTES STDCALL :: TestArray
!DEC$ ATTRIBUTES ALIAS : 'TestArray' :: TestArray
 
 implicit none
 integer*4 Length 
 integer*4 AInteger(1)
 real*8 AReal(1)
 
     integer I
 
c-------Program 
 write(10,*) 'Program test1'
 write(10,*) Length
     do I=1,Length
      write(10,*) AInteger(I)
 end do
 do I=1,Length
 write(10,*) AReal(I)
 end do

 write(10,*) 'End TestArray'
  
end subroutine TestArray

The first loop writing the AInteger array works but when AReal is written I get an access violation. The fort.10 file look like (this is what is written until it adresses the AReal array):

Program test1
 4
 0
 1
 2
 3

[Jugoslav_Dujic]

I'm not positive, but it seems that Delphi does to dynamic arrays the same thing as Fortran for strings (see J. Mansell's post here) -- it passes the length as a hidden argument. As a workaround, declare the arrays in Delphi as scalars by reference, and pass only the first element. That would explain why your single-array call (appers to have) worked (on the price of stack corruption), but the second array just grabs the wrong argument.

[esben_auken]

Hi,

Thanks for your help.

I tried to change the Delpi code to:

procedure TForm1.Button1Click(Sender: TObject);
var
 AInteger : array [1..4] of integer;
 AReal : array [1..4] of double;
 Length : integer;
begin
//Transfer of integer array
 Length:=4;

 for I:=1 to Length do AInteger:=I;
 for I:=1 to Length do AReal:=I*3/2;

 TestArray(Length,AInteger[1],AReal[1])

but with the same result - I still gets an acces violation. I also tried to declare the array in the fortran code to assumed size

integer*4 :: AInteger(*)

real*8 :: AReal(*)
 

but that the same. Do you think I have to give it up?

[Jugoslav_Dujic]

But did you change the dll declaration to:

procedure TestArray(Length: integer; var AInteger: integer; var RReal: double);

That ought to work. You can also print LOC(RReal) (RReal^) on Delphi and Fortran sides and see if they match.

[esben_auken]

You are a hero - it works - thanks for your quick help.

Esben

[esben_auken]

Just for your information - adjustable arrays in Delphi also works:

procedure TestArray(Length: integer; var AInteger: integer; var RReal: double); stdcall; external 'testdll.dll';

procedure TForm1.Button1Click(Sender: TObject);
var
 I, J, LA :integer;

 AInteger : array of integer;
 AReal : array of double;
 Length : integer;
begin

//Transfer of integer and real array
 Length:=4;
 setlength(AInteger,Length);
 setlength(AReal,Length);
 for I:=0 to Length-1 do AInteger:=I;
 for I:=0 to Length-1 do AReal:=I*3/2;

 TestArray(Length,AInteger[0],AReal[0])
end;

And in Fortran

subroutine TestArray(Length,AInteger,AReal)
!DEC$ ATTRIBUTES DLLEXPORT :: TestArray
!DEC$ ATTRIBUTES STDCALL :: TestArray
!DEC$ ATTRIBUTES ALIAS : 'TestArray' :: TestArray
 
 implicit none
 integer*4 Length 
 integer*4 :: AInteger(*)
 real*8 :: AReal(*)
 
     integer I
 
c-------Program 
 write(10,*) 'Program test1'
 write(10,*) Length
     do I=1,Length
      write(10,*) AInteger(I)
 end do
 do I=1,Length
 write(10,*) AReal(I)
 end do

 write(10,*) 'End TestArray'
  
end subroutine TestArray