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Ian Boyd · Guest

i have a COM object written in Delphi, that we can instantiate fine from an
app:

procedure TForm1.Button1Click(Sender: TObject);
var
ClassID: TGUID;
o: IUnknown;
s: IExam;
const
IID_IExam: TGUID = '{7A794786-7C05-4EB4-A071-3D9B170B663A}';
CLSID_TestPaper: TGUID = '{4A75D28A-BCD3-46BF-BE91-361F2F207A10}';
begin
ClassID := CLSID_TestPaper;

o := CreateComObject(ClassID);

// s := o as IExam;
// if Failed(o.QueryInterface(IID_IExam, s) then
// if not Supports(o, IID_IExam, s) then

if Supports(o, IExam, s) then

ShowMessage(' Smile

')
else
ShowMessage(' Sad

');
end;

But if similar code is done from a service, then a call to Supports fails,
as does "as", and using QueryInterface directly returns 0x80004002
(E_NOINTERFACE)

i think the problem has to do with differing apartment models, and so COM is
trying to find some IMarshall interface, but it cannot. But before you think
about that, i'll confuse you with two other theories.

1. You just can't use Delphi COM dll's from a service. Maybe Delphi and it's
global variables (which make accessing visual controls from anything but the
main thread make impossible) make construcing COM objects from a service
impossible. There are global unit level routines, and singleton class
factories.

2. i create my objects during TService.OnStart event. i don't take advantage
of the OnExecute event and spawn worker threads. So, my service is single
threaded; and i STILL call CoInitialize/CoUninitialize during
OnStart/OnStop. So there's no problem there - but at least it can serve to
distract you from what the real problem probably is.

Now back to trying to figure it out. Overriding TComObject's
ObjQueryInterface method, i get to see all the interfaces being asked for by
COM when i try to load the object:

{00000000-0000-0000-C000-000000000046}: SUCCEEDED
{00000003-0000-0000-C000-000000000046}: FAILED
{0000001B-0000-0000-C000-000000000046}: FAILED
{00000000-0000-0000-C000-000000000046}: SUCCEEDED
{00000018-0000-0000-C000-000000000046}: FAILED
{00000019-0000-0000-C000-000000000046}: FAILED
{4C1E39E1-E3E3-4296-AA86-EC938D896E92}: FAILED
{7A794786-7C05-4EB4-A071-3D9B170B663A}: SUCCEEDED

Well that's quite a hodge-podge, but in the end it asks for my own IID, and
it returns.

So what's the rest?

IUnknown: SUCCEEDED
IMarshall: FAILED
"IdentityUnmarshal?": FAILED
IUnknown: SUCCEEDED
IStdMarshallInfo: FAILED
IExternalConnection: FAILED
???: FAILED
IExam: SUCCEEDED

So obviously COM is trying to do some cross apartment stuff. So my question
is, what do i have to do to my COM object so that it is compatible with the
apartment setup by a service?

My COM object is registered with Delphi as:

initialization
ComObjectFactory.Create(ComServer,
TTestPaper, CLSID_TestPaper, 'EyeExam', 'Dummy values changed for
the newgroup post',
ciMultiInstance,
tmApartment);

The last two are of course my concern. Also, my dll has no type library;
which has not been a problem when there was no marshalling. Does Delphi need
me to make a type library in order to automatically support marshalling? Can
Delphi EVER automtically support marshalling? Does TComObject ever get
marshalling ability? Should i be descending from some other type?

Or, more to the point, how can i get my DLL to be truly loaded into the
process space of the service application calling it? What specifically is
the cross-apartment issue?

Dennis Passmore · Guest

I have been using Delphi COM dlls in Delphi NT services for years. I have one Delphi NT Service
project that loads and uses a Delphi COM object that in itself loads and uses MsSql OLEDB as a COM
object and uses QueryInterface with no problems at all.

Dennis Passmore

"Think it might be a new experience and
if you can not Pull then at least Push
the job will get done"

Ian Boyd · Guest

Do your dll's have type libraries?

"Dennis Passmore" <dennisp (AT) nospam_dpassmore (DOT) com> wrote in message
news:g2k8e25hf4g8ab5atr2ujup1osqg06q14u (AT) 4ax (DOT) com...

Dennis Passmore · Guest

Ian Boyd · Guest

Dennis Passmore · Guest

Ian Boyd · Guest