Board index » cppbuilder » Advanced: using a D5 written DLL in C++Builder4

2003-08-01 03:32:34 PM
cppbuilder2
We have written a 'V43lib.dll' in Delhi5 we wish to use in C++Builder 4.
If we try to "follow the rules" we get tons off errors, but if we do the
following it runs (almost) OK.
With Implib we create a V43lib.lib file for this dll.
In a new project under C++Builder4 we use this lib.
Next we add a header file with the translation in C++ (TNsNavigation) of the
Delphi wrapper class decribed below. And the declaration of the
imported functions:
extern "C" {
TNsNavigation* __declspec(dllimport) __stdcall InitNavigation(TComponent
*AOwner);
void __declspec(dllimport) __stdcall FreeNavigation();
}
In the private section of TForm1 (in C++Builder) we have written:
private: // User declarations
TNsNavigation *Paco;
Now comes the serious part:
if we do this in C++Builder:
void __fastcall TForm1::FormCreate(TObject *Sender)
{
Paco = InitNavigation(this);
if ( Paco != NULL ) {
Paco->OnMainObsDownLoadProgres = FUpdateDownLoadMemo;
Paco->OnRouteUpdate = FUpdateRouteInfo;
}
...
}
At the start of the Application we get first an empty dialog as wide as the
screen with an OK button.
If you click OK you get a small dialog with a few 'chaos' characters and an
OK button.
If you click OK next you get access errors.
But if we do this:
void __fastcall TForm1::FormCreate(TObject *Sender)
{
LoadLibrary("V43lib.lib");
Paco = InitNavigation(this);
if ( Paco != NULL ) {
Paco->OnMainObsDownLoadProgres = FUpdateDownLoadMemo;
Paco->OnRouteUpdate = FUpdateRouteInfo;
}
...
}
At the start of the application we first get a message that 'V43Lib.lib' is
not a valid windows image and if we click ok the whole thing runs smoothly
without problems. The first message is correct of course because
'V43Lib.lib' is not a dll but the result of Implib.
The question is how to get rid of this message.
We expected that in Delphi5 we should have written:
function InitNavigation(AOwner:TComponent):TNsNavigation; stdcall;
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF}
procedure FreeNavigation(); stdcall;
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF}
But this results in the same errors as decribed above with the dialogs and
access errors.
In Delphi we have the following situation:
in the interface section of a unit we have:
TNavigatie = class(TComponent)
private
FOnRouteUpdate :TNotifyEvent;
FRouteUpdateEventEnable :boolean;
FOnObstructionsFound :TNotifyEvent;
FObstructionsFoundEventEnable:boolean;
FOnCalculationFail :TNotifyEvent;
...
public
Captions : TCaptions;
MemoStrings : TMemoStrings;
RouteTrack : TRouteTrack;
...
// Main functions/procedures
constructor Create(AOwner:TComponent); override;
destructor Destroy; override;
function MainObstructionsFileDate():string;
function MainObstructionsCreationDate():string;
function MainDownLoadObstructions():boolean;
...
published
// Main Properties
property OnMainObsDownLoadProgres :TFtpProgresEvent read
FOnMainObsDownLoadProgres write FOnMainObsDownLoadProgres;
property MainSelectedRoute :integer read FSelectedRoute;
// Route Properties
property OnRouteUpdate :TNotifyEvent read FOnRouteUpdate
write FOnRouteUpdate;
property OnRouteObstructionsFound :TNotifyEvent read
FOnObstructionsFound write FOnObstructionsFound;
...
end;
To export this class we've written
a wrapper in wich we wrap the properties and methods we want to export:
{$Define V43Lib}
TNsNavigation = class(TObject)
private
//MAIN
FOnMainObsDownLoadProgres:TFtpProgresEvent;
//SHIPS
FOnShipsListUpdate :TNotifyEvent;
FOnShipsShipUpdate :TNotifyEvent;
//ROUTE
FOnRouteUpdate :TNotifyEvent;
...
public
{$IFDEF V43Lib}
Constructor Create();
{$ENDIF}
//MAIN
function MainGetCopyright: string; virtual;
stdcall; {$IFNDEF V43Lib} abstract; {$ENDIF}
Function MainDownLoadObstructions():Boolean; virtual;
stdcall; {$IFNDEF V43Lib} abstract; {$ENDIF}
procedure MainApplyDownloadedObstructions(); virtual;
stdcall; {$IFNDEF V43Lib} abstract; {$ENDIF}
procedure MainCancelDownloadedObstructions(); virtual;
stdcall; {$IFNDEF V43Lib} abstract; {$ENDIF}
...
published
//MAIN
property OnMainObsDownLoadProgres :TFtpProgresEvent read
FOnMainObsDownLoadProgres write FOnMainObsDownLoadProgres;
//SHIPS
property OnShipsListUpdate :TNotifyEvent read
FOnShipsListUpdate write FOnShipsListUpdate;
end;
function InitNavigation(AOwner:TComponent):TNsNavigation;
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF}
procedure FreeNavigation();
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF}
//according to the rules this should be:
{function InitNavigation(AOwner:TComponent):TNsNavigation; stdcall;
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF}}
{procedure FreeNavigation(); stdcall;
{$IFNDEF V43Lib} external 'V43lib.dll' {$ENDIF} }
// now we declare 2 vars
Var
GNavigatie : TNavigatie;
GNsNavigation : TNsNavigation;
// In the implementation section we do this:
implementation
// Internal
constructor --------------------------------------------------------
constructor TNsNavigation.Create();
begin
inherited Create();
// Definitions of the event properties:
GNavigatie.OnMainObsDownLoadProgres := FSendMainObsDownLoadProgresEvent;
GNavigatie.OnRouteUpdate := FSendRouteUpdateEvent;
...
end;
...
function TNsNavigation.MainGetCopyright: string;
Begin
Result:=CopyRight
end;
Function TNsNavigation.MainDownLoadObstructions():Boolean;
Begin
Result:=GNavigatie.MainDownLoadObstructions();
end;
procedure TNsNavigation.MainApplyDownloadedObstructions();
Begin
GNavigatie.MainApplyDownloadedObstructions();
end;
...
// Finally we do this:
// External
constructor --------------------------------------------------------
function InitNavigation(AOwner:TComponent):TNsNavigation;
begin
...
if Assigned(GNavigatie) then
GNsNavigation := nil
else
begin
GNavigatie := TNavigatie.Create(AOwner);
GNsNavigation := TNsNavigation.Create();
end;
result := GNsNavigation
end;
// External
destructor --------------------------------------------------------
procedure FreeNavigation();
begin
...
if Assigned(GNavigatie) then
begin
GNavigatie.Free;
GNsNavigation.Free;
end;
end;
// In the library unit we do this
uses
ShareMem,
SysUtils,
Classes,
unitAsDecribedAvove,
...
;
{$R *.RES}
Exports
InitNavigation,
FreeNavigation;
begin
end.
I hope someone can help us out of this problem.
Thanks in advance,
Peter Feenstra
 

Peter Feenstra wrote:
important information: what's the type of TFtpProgresEvent ?
Anyway in these situations the most important thing is to keep dll and exe
code completely isolated. Don't use sharemem (are they the same for builder
4 and Delphi 5 ?), don't pass "AnsiString"s, pass "char *"s (is the
implementation of AnsiString of Builder 4 compatible with the implementation
of Delphi 5 ?) and in general never allow anything allocated from the dll
code to be deallocated from the exe code and vise versa.
Also some other questions:
Is the internal structure of TObject the same for builder 4 and delphi 5 ?
Is TComponent the same ? ... and all the components you seem you are using
from both sides?
Cheers.
Sam.
--
Please remove "sam_" from email address.