HRESULT CDemo::Div(/*[in]*/ LONG a, /*[in]*/LONG b, /*[out,retval]*/ LONG* pRet)
{
    if (pRet == NULL)
        return E_POINTER;

    if (b == 0)
    {
        *pRet = 0; // is this redundant?
        return E_INVALIDARG;
    }

    *pRet = a/b;
    return S_OK;
}

ISmth *pSmth = NULL;
pObj->GetSmth(&pSmth); // HRES is ignored
if (pSmth) // Assumes that if GetSmth failed then pSmth is still NULL
{
    pSmth->Foo();
    pSmth->Release();
}

HRESULT GetSmth( [out] ISmth** );