runtime error when setting pointer to interface to NULL

From:

"Daniel" <newsonly@cableone.net>

Newsgroups:

microsoft.public.vc.language

Date:

Fri, 25 Jul 2008 23:31:17 -0500

Message-ID:

<eV$rzht7IHA.5596@TK2MSFTNGP02.phx.gbl>

I am getting an error when I try to run the following code when I set the
variable to NULL?

#import "..\Orchestra\Orchestra\Debug\Orchestra.dll"

using namespace OrchestraLib;

DWORD WINAPI ThreadFunction(LPVOID lpvParameter);

int _tmain(int argc, _TCHAR* argv[])

{

::CoInitializeEx(NULL,COINIT_APARTMENTTHREADED);

IClarinetPtr spIClarinet;

spIClarinet.CreateInstance(__uuidof(Clarinet));

spIClarinet->Sound(1000, 1000);

spIClarinet->Release();

spIClarinet = NULL;

The error happens in comip.h at the point below:

template<> _com_ptr_t& operator=(Interface* pInterface) throw()

{

if (m_pInterface != pInterface) {

Interface* pOldInterface = m_pInterface;

m_pInterface = pInterface;

_AddRef();

if (pOldInterface != NULL) {

pOldInterface->Release();
<---------------------------------------------------||||||||||||

}

}

return *this;

}

The error happens when I debug the code. It's a runtime error. Here's the
message it gives me:

Unhandled exception at 0x00412076 in Test.exe: 0xC0000005: Access violation
reading location 0xfeeefef6.

If anyone could tell me anything, I would really appreciate it. The .dll
file is one that I created with ATL 8. I use VS2008.

Daniel