compilation error when using CComPtr w/ CUnknown-derived objects

Windows XP Pro SP2
VC++ 2005 Pro SP1
Microsoft Platform SDK for Windows Server 2003 R2

Hello,

In my project I've got many classes derived from CUnknown. With some I have
no problem and with some others I get a compilation error when I attempt a
simple assignment. The compilation error occurs when the CComPtr declaration
is either global or on a different line from the class instantiation. See a
sample class below and two examples, the first example compiles OK while the
second gives the error message below.

There may be something obvious but I'm blind. I cannot see a difference
between the classes that work and the ones that fail. Can you figure out why
I get this compilation error? Any idea would be very welcome! Thank you.
No?l

// Sample class

class CTest : public CUnknown
{
public:
DECLARE_IUNKNOWN

CTest(void) :
CUnknown(_T("CTest"), NULL)
{
}

CTest(LPUNKNOWN pUnk, HRESULT* phr) :
CUnknown(_T("CTest"), pUnk, phr)
{
}

CUnknown * WINAPI CreateInstance(LPUNKNOWN punk, HRESULT *phr)
{
ASSERT(phr);
CTest *pNewObject = new CTest(punk, phr);
if (pNewObject == NULL) {
if (phr)
*phr = E_OUTOFMEMORY;
}

return pNewObject;
}

....

};

// Example 1: compilation succeeds
// CComPtr and CreateInstance in the same line

void Instantiate(void)
{
HRESULT hr = S_OK;
CComPtr<CTest> pTest = reinterpret_cast<CTest*>(CTest::CreateInstance(NULL,
&hr));
....
}

// Example 2: compilation fails
// CComPtr and CreateInstance on the different lines, CComPtr global

CComPtr<CTest> pTest;

void Instantiate(void)
{
HRESULT hr = S_OK;
pTest = reinterpret_cast<CTest*>(CTest::CreateInstance(NULL, &hr));
....
}

// Example 2 -compilation error in VC++ 2005:

1>c:\program files\microsoft visual studio
8\vc\atlmfc\include\atlcomcli.h(278) : error C2664: 'ATL::AtlComPtrAssign' :
cannot convert parameter 2 from 'CTest *' to 'IUnknown *'
1> Types pointed to are unrelated; conversion requires reinterpret_cast,
C-style cast or function-style cast
1> c:\program files\microsoft visual studio
8\vc\atlmfc\include\atlcomcli.h(275) : while compiling class template member
function 'CTest *ATL::CComPtr<T>::operator =(T *) throw()'
1> with
1> [
1> T=CTest
1> ]
1> d:\sources\test\test.h(94) : see reference to class template
instantiation 'ATL::CComPtr<T>' being compiled
1> with
1> [
1> T=CTest
1> ]

--
No?l
http://noeld.com/