Implementation two interfaces in one class

[venkatesh52867]

Hi, Problem is this || IID_ICredentialProviderSetUserArray when i call IID_ICredentialProviderSetUserArray interface through Quareyinterface dll is crashing without implementing ICredentialProviderSetUserArray interface dll is working is fine . thanks

[Lost User]

I'm sorry, but no one can guess what your code is doing to cause the crash. As I said before, use your debugger to trace through it and identify exactly what is happening.

Use the best guess

[venkatesh52867]

Hi, please check this code.i am highlighted with bold that code add then it is crashing. #pragma once #include #include #include #include "PasswordResetCredential.h" #include "helpers.h" class CSampleProvider : public ICredentialProvider,public ICredentialProviderSetUserArray { public: // IUnknown STDMETHOD_(ULONG, AddRef)() { return _cRef++; } STDMETHOD_(ULONG, Release)() { LONG cRef = _cRef--; if (!cRef) { delete this; } return cRef; } STDMETHOD (QueryInterface)(REFIID riid, void** ppv) { HRESULT hr; if (IID_IUnknown == riid || IID_ICredentialProvider == riid ||IID_ICredentialProviderSetUserArray==riid) { *ppv = this; reinterpret_cast(*ppv)->AddRef(); hr = S_OK; } else { *ppv = NULL; hr = E_NOINTERFACE; } return hr; } public: IFACEMETHODIMP SetUsageScenario(CREDENTIAL_PROVIDER_USAGE_SCENARIO cpus, DWORD dwFlags); IFACEMETHODIMP SetSerialization(const CREDENTIAL_PROVIDER_CREDENTIAL_SERIALIZATION* pcpcs); IFACEMETHODIMP Advise(__in ICredentialProviderEvents* pcpe, UINT_PTR upAdviseContext); IFACEMETHODIMP UnAdvise(); IFACEMETHODIMP GetFieldDescriptorCount(__out DWORD* pdwCount); IFACEMETHODIMP GetFieldDescriptorAt(DWORD dwIndex, __deref_out CREDENTIAL_PROVIDER_FIELD_DESCRIPTOR** ppcpfd); IFACEMETHODIMP GetCredentialCount(__out DWORD* pdwCount, __out DWORD* pdwDefault, __out BOOL* pbAutoLogonWithDefault); IFACEMETHODIMP GetCredentialAt(DWORD dwIndex, __out ICredentialProviderCredential** ppcpc); IFACEMETHODIMP SetUserArray (__in ICredentialProviderUserArray * users); friend HRESULT CSampleProvider_CreateInstance(REFIID riid, __deref_out void** ppv); protected: CSampleProvider(); __override ~CSampleProvider(); private: void _CleanUpAllCredentials(); private: LONG _cRef; CSampleCredential **_rgpCredentials; // Pointers to the credentials which will be enumerated by this // Provider. ICredentialProvider *_pWrappedProvider; // Our wrapped provider.

[Lost User]

Please format your code properly between <pre> tags, like:

STDMETHOD_(ULONG, Release)()
{
LONG cRef = _cRef--;
if (!cRef)
{
delete this;
}
return cRef;
}

Use the best guess

[Lost User]

if (IID_IUnknown == riid ||
IID_ICredentialProvider == riid ||
IID_ICredentialProviderSetUserArray)
{

Do you see something missing here?

Use the best guess

[venkatesh52867]

hi, ok but that is not problem when i called ICredentialProviderSetUserArray ==riid probblem is occurring if (IID_IUnknown == riid || IID_ICredentialProvider == riid || IID_ICredentialProviderSetUserArray ==riid) { Thanks

[Lost User]

You really need to do this[^]. Without a lot more information about what is actually happening at the time of the crash it's anyone's guess.

Use the best guess

[Lost User]

www.163.com

[ExcellentOrg]

Richard, Venkatesh Are you certain that the old object is not getting out of scope when you create new. When you create multiple objects, chances are that you are not maintaining reference counts correctly so there is a small chance that object is actually removed or marked for removal when client attempts to access ... As Richard quotes, this is my best guess :)

[Lost User]

It's been over a month; one can only assume OP fixed their code.

Use the best guess

[H Pham]

The issue might lie in this statement: *ppv = this; Because you use a C-cast to type void*, type information is lost. The pointer does not point to the correct virtual table of the interface that you want to return. Try the following instead:

STDMETHOD (QueryInterface)(REFIID riid, void** ppv)
{
HRESULT hr;
if (IID_ICredentialProviderSetUserArray == riid)
{
*ppv = dynamic_cast<ICredentialProviderSetUserArray>( this );
reinterpret_cast<IUnknown*>(*ppv)->AddRef();
hr = S_OK;
}
else if (IID_IUnknown == riid ||
IID_ICredentialProvider == riid )
{
*ppv = dynamic_cast<ICredentialProvider>( this );
reinterpret_cast<IUnknown*>(*ppv)->AddRef();
hr = S_OK;
}
else
{
*ppv = NULL;
hr = E_NOINTERFACE;
}
return hr;
}

[DriveByCoder]

If you have a C++ class

class Z : public X, public Y
{
};

then you may be surprised to find that

this

is not a pointer to Y. Basic C++. But

static_cast(this)

is. You need a separate

if(riid == IID_...){...}

for each IID