COM problem between Unmanaged C++ and Delphi - c++

Question

I have a DLL in unmanaged C++ :
EditArticleManagerFactory.h:
class __declspec(dllexport) EditArticleManagerFactory : public NamedClassFactory<SCEditArticleManager>,
public SCBLEditArticle:ICOMEditArticleManagerFactory
{
public:
STDMETHODIMP CreateManager(BSTR bstrName, SCBLEditArticle::ICOMEditArticleManager** pEditArticleManager);
}
interface ICOMEditArticleManagerFactory : IUnknown
{
HRESULT CreateManager([in]BSTR bstrName, [out]ICOMEditArticleManager** pEditArticleManager);
}
EditArticleManagerFactory.cpp:
STDMETHODIMP EditArticleManagerFactory::CreateManager(BSTR bstrName, SCBLEditArticle::ICOMEditArticleManager** pEditArticleManager)
{
manager = factory->createManager(bstrName);
return manager->QueryInterface(__uuidof(SCBLEditArticle::ICOMEditArticleManager), (void**)&pEditArticleManager);
}
I'd like to call this method from Delphi and it should return an interface to a created manager.
Delphi:
function CreateManager(bstrName: wideString; pEditArticleManager: ICOMEditArticleManager): HResult; stdcall; external 'SCBLEditArticle.dll';
procedure CreateManager;
var
hr:HResult;
mCOMEditArticleManager: ICOMEditArticleManager;
begin
hr := CreateManager('MANAGER1', mCOMEditArticleManager);
end;
The problem is I get an access violation when it reaches the end; in this delphi method.
Do you have any ideea what could be wrong?
Thx, rufusz
Edit:
But I'm using a macro for implementing Release and
EditArticleManagerFactory.h :
IMPLEMENT_UNKNOWN_NODELETE(EditArticleManagerFactory) BEGIN_INTERFACE_TABLE(EditArticleManagerFactory) IMPLEMENTS_INTERFACE(SCBLEditArticle::ICOMEditArticleManagerFactory) END_INTERFACE_TABLE()
Inttable.cpp:
define IMPLEMENT_UNKNOWN_NODELETE(ClassName) \
STDMETHODIMP QueryInterface(REFIID riid, void **ppv) \ { \ HRESULT hr = InterfaceTableQueryInterface(this, GetInterfaceTable##ClassName(), riid, ppv);\ __if_exists(InheritedQueryInterface##ClassName) { if ( FAILED(hr) ) hr = InheritedQueryInterface##ClassName(riid, ppv); } \ return hr; \ }\ STDMETHODIMP_(ULONG) AddRef(void) { return 2; } \ STDMETHODIMP_(ULONG) Release(void) { return 1; }
Furthermore :
When I debug from Delphi, I get the access violation in the UnsetExceptionHandler
004046F7 3901 cmp [ecx],eax.
Maybe this can help to diagnose the problem.
Also if I declared an external function outside my C++ class, and called that from Delphi, I didn't get the access violation, but didn't get the interface pointer neither.
Also:
If I do nothing in the C++ method, I still get the AccessViolation.

Answer 1

Should be
function CreateManager(bstrName: wideString; OUT pEditArticleManager: ICOMEditArticleManager): HResult; stdcall; external 'SCBLEditArticle.dll';
Notice the "OUT", you somehow dropped a indirection. (an interface is only one *, not two)

Answer 2

It's odd you try to declare STDMETHODIMP CreateManager within your class in C++, this may be causing trouble.
Also COM provides a standard way of having an object-factory (class-object), which responds to CoCreateInstance calls, you may want to have a look at that.

Answer 3

Most likely there's something wrong with the reference counting.
When the function exists, the reference count to all interfaces is decremented. The Delphi compiler automatically creates the necessary code to call ICOMEditArticleManager::Release.
Either its implementation is flawed or you are not returning a valid IUnknown interface.
You can try the following:
In VC++ set a breakpoint at the implementation of ICOMEditArticleManager::Release
In Delphi switch to the CPU mode and single-step through the disassembled code.
That way you should find the cause or at least narrow it down.