[fpc-pascal] Poss FPC Bug

[Justin Smyth]

Guys I need some help here , can some shed some light on this issue  ?


I've got my own test dll with this function declared as an export


function GetCLSID(clsid:TGUID):Integer;stdcall;
begin
  clsid := TESTGUID;
  Result := S_OK;
end;

My testguid  = '{3F5A62E1-1112-1100-A075-CC7364CAE42A}'

and in my test application i have DLL call to this function

function GetGuid(var MyGuidTest: TGUID): Integer;
var
  Res:Integer;
begin
  Load;
  Res := PGetGuid(MyGuidTest);
  if Res = S_OK then
  begin
    Result := res;
  end;
  Unload;
end;

and PGetGuid is defined as

PGetGuid    : TFunctionGetGUID; which TFunctionGetGUID = function 
(MyGuid:TGUID):Integer;StdCall;

I call this function above

 MyGUid := GUID_NULL;
 GetGuid(MyGuid);
 LabelResult1.Caption := GUIDToString(MyGuid);


The Result of GetGuid is ALLWAYS GUID_NULL unless i change the DLL call to 
be like this

function GetCLSID(out clsid:TGUID):Integer;stdcall;
begin
  clsid := TESTGUID;
  Result := S_OK;
end;


This relates to Ipersist.GetClassID which needs to be defined like this

Function GetClassId(Out clsid:TClsId):HResult; StdCall;

but its defined as

Function GetClassId(clsid:TClsId):HResult; StdCall;

which is a show stopper in my app it work work because the DeskBand.DLL cant 
see which CSLID it is because the value never gets returned....


Delphian
----- Original Message ----- 
From: "Flávio Etrusco" <flavio.etrusco at gmail.com>
To: "Justin Smyth" <delphian at smythconsulting.net>; "FPC-Pascal users 
discussions" <fpc-pascal at lists.freepascal.org>
Sent: Tuesday, April 06, 2010 9:56 AM
Subject: Re: [fpc-pascal] Poss FPC Bug.


On Mon, Apr 5, 2010 at 8:29 PM, Justin Smyth
<delphian at smythconsulting.net> wrote:
> guys i've been working on a port of an application that uses the Com
> IPersist Interface , one of its procedures seems to be wrong ,
>
>
> Function GetClassId(clsid:TClsId):HResult; StdCall;
>
> yet i believe it should be
>
> Function GetClassId(out clsid:TClsId):HResult; StdCall
>
> i've checked the MSDN and it says it should be returning a value -
>
> its defined in C++ as
>
> HRESULT GetClassID([out]  CLSID *pClassID);
>
> pClassID [out]
>
> A pointer to the location that receives the CLSID on return. The CLSID is 
> a
> globally unique identifier (GUID) that uniquely represents an object class
> that defines the code that can manipulate the object's data.
>
> Delphian
>
> Ps if i change this in the code , its the FPC that needs to be re complied 
> ?
>

I've fallen victim of the same 'trap' on a similar function. Arrays
are passed "by reference" automatically in 'stdcall' calling
convention.

Flávio