Re: ATL com server can pass interface as parameters?
ceasar.tw@gmail.com wrote:
Server side
========
class CMy2 : IMy2
{
// IUnknown
HRESULT STDMETHODCALLTYPE QueryInterface(const IID& iid, void**
ppv) { return S_OK; }
You never set *ppv to anything, and yet you return S_OK. After the call
to QueryInterface, the client would try to use the value in *ppv (that's
why they called QI in the first place, after all), and would crash.
ULONG STDMETHODCALLTYPE AddRef() { return 1; }
ULONG STDMETHODCALLTYPE Release() { return 1;
// IDispatch
HRESULT STDMETHODCALLTYPE GetTypeInfoCount(UINT *pctinfo){ return
S_OK; };
HRESULT STDMETHODCALLTYPE GetTypeInfo(UINT iTInfo, LCID lcid,
ITypeInfo **ppTInfo){ return S_OK; };
HRESULT STDMETHODCALLTYPE GetIDsOfNames(REFIID riid, LPOLESTR
*rgszNames, UINT cNames, LCID lcid, DISPID *rgDispId){ return S_OK; };
HRESULT STDMETHODCALLTYPE Invoke(DISPID dispIdMember, REFIID riid,
LCID lcid, WORD wFlags, DISPPARAMS *pDispParams, VARIANT *pVarResult,
EXCEPINFO *pExcepInfo, UINT *puArgErr){ return S_OK; };
};
CMy2 csMy2;
STDMETHODIMP CMy1::GetInterface(IMy2 **pVal)
{
CMy2 *p = &csMy2;
*pVal = (IMy2 *)&p;
Your GetInterface ends up returning an address of the local variable p,
not the address of csMy2. As soon as the function returns, the address
becomes garbage. If you insist on abusing COM this way, at least make it
*pVal = &csMy2;
--
With best wishes,
Igor Tandetnik
With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925