[fpc-pascal] AsciiZ confusion

[afpTeam]

Hi,

Sorry this is a long message, but hard to explain.  I have a DLL I wrote in 
FreePascal 2.0.2, which is communicating between a Delphi program and a 
PowerBasic Dll, like follows...

PBdll exports PBSub ByRef as AsciiZ   <> MyFreePascall_DLL <> 
DelphiDLLstubByRef_Variants

As noted, the Delphi Program integrates a DLL stub which forces me to make 
calls using it's pre-defined "Variants Only" format.

The problem comes when I pass data into FPC via "parameters" byRef through a 
procedure, into the PowerBasic DLL. The first parameter returns unmodified 
and the second parameter returns only one character wide, as if FPC is 
trying to receive back a pointer only, to the string space where the PB data 
resides.  Or possibly it's just garbage and looks this way.

The FPC DLL is setup as follows:
============================

{$LONGSTRINGS ON}

library DelphiXchg;

uses Variants, strings;

//Declare PowerBasic external (a sub or function call, made no difference)
procedure subXchngAsciiZ(Data1, DATA2:string)stdcall;external 'PB.DLL';

//Declare the Delphi calling stub DLL (variants only);
function Delphstub(var vD1,vD2:variant):variant;stdcall;export;

//at runtime, Delphi sends in... vD1:='test'; vD2:='  '; // (vD2 is 
place-held with a 'space')

begin
    if vD1 = 'test'                                    // vD1 is being sent 
from Delphi
        then subXchngAsciiZ(vD1, vD2);  // call out to PB DLL
                                                            // vD1 should 
come back 'tested'
                                                            // vD2 should 
come back 'good'
end;

exports
Delphstub;        // FPC Return value unused

begin
end.

==========================
When the Delphi calling program sends in the variant vD1:='test', (through 
FPC to the PB DLL), FPC only gets back 'test' unmodified and variant vD2 is 
coming back as 'g', (only the first character, instead of 'good', (ahhh but 
vD2 did get modified at least)).

I thought that zero or null terminated AsciiZ data would handle the string 
array length automatically in FPC, on < 255 wide, but now I'm supposing I 
may have to break the variants out, use explicit calls internally by typed 
pointer reference and then reload the outgoing variants with the result data 
from the pointers to the explicit variables before returning, but I've had 
no success in figuring out how to set that up correctly.

Should it really be that much handling to pass AsciiZ on Variant types as 
parameters, or am I overlooking something stupid simple?  The only example I 
have to go by is a VB program that makes calls directly across to PB, using 
ByRef ASCIIZ, so the problem seems mostly from being forced to use the 
Variant types in parameters from the Delphi calling program.

Thanks for any ideas.

AFP 



---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 0635-3, 08/31/2006
Tested on: 8/31/2006 1:49:00 PM
avast! - copyright (c) 1988-2006 ALWIL Software.
http://www.avast.com