Unable to Create 64 bit DLL in Windows
lazarus / 34-Windows

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williamda · 2011-07-28 22:02

Hello,

I´m new to Lazarus. I´m moving from Delphi looking for a 64 bit
compiler. I really believe Embarcadero has lost the directions with
DElphi developing and Lazarus/FPC looks more promising.

My first project is to create a 64 bit DLL in Lazarus and call it from
another Lazarus application. But I get a SISEGV error whenever I try
to call it with early or late binding. I´ve found that the debugger
still doesn´t work in 64 bit Windows.

Creating/calling a 64 bit DLL can be done with Lazarus. I tried with
oficcial release 0.93 and Lazarus trunk, but none of these worked.

--- This is the exported function

function Hola: Int64; stdcall; export;
begin
  Result := 22;
end; 


---- This is the call

// Early Binding

function Hola: Int64; external 'testhola.dll';

procedure TForm1.Button4Click(Sender: TObject);
var
  Res : Int64;
begin
  Res := Hola();
  lbLoadStatus.caption := 'Hola Retorna :' + IntToStr(res);
end; 

// Late Binding

procedure TForm1.Button3Click(Sender: TObject);
type
  THola = function(): Int64; stdcall;
var
  Hola: THola;
  res: Int64;
begin
  FDLLHandle := LoadLibrary( PChar(S) );
  if FDLLHandle < HINSTANCE_ERROR then
    lbLoadStatus.Caption := SystemErrorMessage + ' (Error ' +
IntToStr(GetLastError) + ')'
  else
    lbLoadStatus.Caption := 'DLL cargada exitosamente';

  Hola := THola(GetProcAddress(FDLLHandle, 'Hola'));

  {if procedure is found in the dll}
  if not Assigned(@Hola) then
  begin
    lbLoadStatus.caption := SystemErrorMessage + ' (Error ' +
IntToStr(GetLastError) + ')'
  end
  else
  begin
    Res := Hola();
    lbLoadStatus.caption := 'Hola Retorna :' + IntToStr(res);
  end;
end;


Thanks for your answers,

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felipemdc · 2011-07-30 20:20

Have you tryed using FPC Trunk? Which FPC versions have you tried?
Changing Lazarus itself shouldn't change anything here, the important
is the version of FPC.

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Leledumbo · 2011-07-31 07:12

Code: [Select]--- This is the exported function

function Hola: Int64; stdcall; export;

...

---- This is the call

// Early Binding

function Hola: Int64; external 'testhola.dll';
You miss stdcall in the external declaration.

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williamda · 2011-08-02 21:56

You´re right, I missed to put stdcall at the external definition. I
fixed it, but still get the same error  (0xc000007b) when launching
the application.

I also downloaded the fpc trunk, but I don´t now how to make it work
with Lazarus. I´ll appreciate some advice or a link to learn how .

Thanks for your replies,

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Martin_fr · 2011-08-02 22:38

1) Debugging: If you use FPC trunk; and Lazarus trunk, then it should
work.
But make sure your anti-virus does not interfere.

2) On 32 bit (but may happen on 64 bit too, don't know), I had once
problems with dll. Turned out that bitdefender (Antivirus) just
deleted the dll file => without warning, and despite all settings,
saying to *always* ask first. Maybe ?

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Marc · 2011-08-03 07:21

1) How did you declare FDLLHandle ? some handle types are still
defined 32 bit on a 64bit windows.

2) (iirc) check for Assigned(Hola) instead of Assigned(@Hola)