GCC C++ Classes

[rtusrghsdfhsfdhsdfhsfdhs]

How can I use these GCC classes in FPC? With something like CORBA interfaces?

A small example for both sides would be welcome.

Thanks

[Leledumbo]

There' s a little preliminary support with restrictions.

[rtusrghsdfhsfdhsdfhsfdhs]

This works good in Delphi XE7 / Visual C++ but crashes in FPC Trunk? 



I get some SIG error.

Code: [Select]

program Test;

//{$APPTYPE CONSOLE}
{$mode delphi}

const
  DLL = 'C:\Users\Administrator\Desktop\Interop\DLL-CPP\Interface\Debug\Interface.DLL';

type
  TPerson = class
    function Age(): Integer; overload;  virtual; cdecl; abstract;
    procedure Age(const Value: Integer); overload; virtual; cdecl; abstract;
    procedure Free; overload; virtual; cdecl; abstract;
  end;

function NewPerson(): TPerson; cdecl; external DLL;

var
  Person: TPerson;
begin
  Person := nil;
  Person := NewPerson;

  if Person = nil then
  Writeln('not initalized');

  Person.Age(22);
  Writeln(Person.Age);
  Person.Free;
  Person := nil;
  Readln;
end.




#include "stdafx.h"
#include <iostream>

using namespace std;

class AbstractPerson
{
virtual void _cdecl Age(const int Value) = 0;
virtual int _cdecl Age() = 0;
virtual void _cdecl Free() = 0;
};

class Person : public AbstractPerson
{
private:
int FAge;
public:
void  _cdecl Age(const int Value) { FAge = Value; };
int  _cdecl Age() { return FAge; };
void _cdecl Free() { if (this) delete this; };

Person() { FAge = 0; };
    ~Person() {};
};
 
extern "C" __declspec(dllexport)  AbstractPerson* __cdecl NewPerson()
{
return new Person();
}
 

[Leledumbo]

This works good in Delphi XE7 / Visual C++ but crashes in FPC Trunk? 

• That's not how FPC supports it, please read the thread link above
• Delphi perhaps decided to follow VC++ VMT layout (this is implementation specific that's not even compatible among C++ compilers), therefore it works in Delphi. Simply changing C++ compiler to compile the DLL is enough to crash it

[rtusrghsdfhsfdhsdfhsfdhs]

So FPC cannot use ActiveX? Because interfaces are really abstract classes with some extra functionality..

Besides I made it work with GCC On delphi ofcourse.

[Leledumbo]

So FPC cannot use ActiveX? Because interfaces are really abstract classes with some extra functionality..

ActiveX is supported, you can use LazActiveX to import ActiveX libraries. However, as you will read in the wiki, it's Windows only. FPC can deal with CORBA interface, if you want something more universal.

[skalogryz]

So FPC cannot use ActiveX? Because interfaces are really abstract classes with some extra functionality..

Interfaces are not abstract classes. They're VMTs, where VMT is following certain convention.
ActiveX is implemented based of COM interfaces (where COM is the convention). There're also CORBA interfaces (and they're incompatible with COM interfaces, since the convention is different).

ActiveX interfaces are not C++ classes.. and FPC does support COM and ActiveX

[rtusrghsdfhsfdhsdfhsfdhs]

Please make an example how to use CORBA interfaces then.. i never used them.

Look what someone posted on http://www.hu.freepascal.org/lists/fpc-devel/2005-January/004403.html

Well, interfaces are really C++ abstract classes. COM model adds some bell and
whistles above that (including IUnknown that is integrated in object pascal
language interfaces). 

This is totally incorrect statement. Inprocess COM is heavy relayed on C++
abstract classes. I'm not talking here about ActiveX (it's really just a
framework above COM), marshalling, etc.

[rtusrghsdfhsfdhsdfhsfdhs]

I tested COM with FPC its not even compatible with Delphi.. 
So much for compatibility

Code: [Select]

{DELPHI}

library Project1;

uses
  System.SysUtils;

type
  IPerson = interface ['{6675C5C0-D95C-11D4-BDE0-00A024BAF736}']
    function Age(): Integer; overload; stdcall;
    procedure Age(const Value: Integer); overload; stdcall;
  end;

  TPerson = class(TInterfacedObject, IPerson)
  private
    FAge: Integer;
  public
    procedure Age(const Value: Integer); overload; stdcall;
    function Age(): Integer; overload; stdcall;
  end;

procedure TPerson.Age(const Value: Integer);
begin
  FAge := Value;
end;

function TPerson.Age(): Integer;
begin
  Result := FAge;
end;

function CreatePerson(): IPerson; stdcall; export;
begin
  Result := TPerson.Create;
end;

exports
  CreatePerson;

begin

end.

{FREEPASCAL}

program Project1;

{$mode delphi}

uses
  Classes;

type
  IPerson = interface ['{6675C5C0-D95C-11D4-BDE0-00A024BAF736}']
    function Age(): Integer; overload; stdcall;
    procedure Age(const Value: Integer); overload; stdcall;
  end;

const
  DLL = 'C:\Users\Administrator\Desktop\DLL\Win32\Release\Project2.dll';

function CreatePerson(): IPerson; stdcall; external DLL;

var
  Person: IPerson;
  I: Integer;
begin
  Person := CreatePerson();
  Person.Age(10); // EXTERNAL SIGV CRASH
  I := Person.Age;
  Readln;
end.
           


[skalogryz]

Works just fine with D7 and fpc 2.6.4

[rtusrghsdfhsfdhsdfhsfdhs]

It doesn't work with XE7 & FPC Trunk..

[skalogryz]

It doesn't work with XE7 & FPC Trunk..

Assembler is your friend then. 
Expected problem - interface is being released on returning from CreatePerson function. Should you use out parameter?

Code: [Select]

procedure CreatePerson(out person: IPerson)

[rtusrghsdfhsfdhsdfhsfdhs]

I tried out and var. Still crashes. Seems this is either a bug in trunk or something else.

[skalogryz]

I tried out and var. Still crashes. Seems this is either a bug in trunk or something else.

XE7 maybe? ... try an earlier version of FPC?
Btw, what CPU i386 or x86_64?

Try this:
// library side

Code: [Select]

function CreatePerson(): IPerson; stdcall; export;
begin
  Result := TPerson.Create;
  writeln( NativeInt ( Result ));
end;
// program size

Code: [Select]

var
  Person: IPerson;
  I: Integer;
begin
  Person := CreatePerson();
  writeln( PtrUInt( Person ) );
  Person.Age(12); // EXTERNAL SIGV CRASH
  I := Person.Age;
  writeln(I);
  Readln;
end.
numbers should match in the first place.

[rtusrghsdfhsfdhsdfhsfdhs]

Windows 8.1 x64 + Intel Q6600  + FPC Trunk x86. But will try 2.6.4 I have doubts.

On Delphi I get number in console but in FPC none