Microsoft KB Archive/168009

= FIX: Smartptr Property in Interface Causes C2512 Error =

Article ID: 168009

Article Last Modified on 10/24/2003

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APPLIES TO


 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition

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This article was previously published under Q168009



SYMPTOMS
The compiler may incorrectly issue error C2512 when a class has a _declspec(property) member. Having a _declspec(property) member is common when you import type-libraries with #import. In addition to error C2512, warnings C4510, C4511, C4512, C4513 and C4610 may also be generated.



RESOLUTION
This can be avoided when doing #import by using the attributes raw_interfaces_only or no_native_types. Unfortunately, this also turns off major functionality.



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97, Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why



MORE INFORMATION
The first sample below causes the compiler to give the following messages when compiled at warning level 4:

warning C4510: 'B' : default constructor could not be generated

warning C4610: struct 'B' can never be instantiated - user defined

constructor required

error C2512: 'B' : no appropriate default constructor available

Sample Code A
// Compile option needed /W4 class A  {  A; };  struct B   {  __declspec( property (get=getA)) A a;      A getA; };  void f {     B b;   } The second sample generates the following errors:

warning C4510: 'IA' : default constructor could not be generated

warning C4511: 'IA' : copy constructor could not be generated

warning C4512: 'IA' : assignment operator could not be generated

warning C4513: 'IA' : destructor could not be generated

warning C4610: struct 'IA' can never be instantiated - user defined constructor required

warning C4510: 'CA' : default constructor could not be generated

warning C4511: 'CA' : copy constructor could not be generated

warning C4512: 'CA' : assignment operator could not be generated

warning C4513: 'CA' : destructor could not be generated

warning C4610: class 'CA' can never be instantiated - user defined constructor required

error C2512: 'CA' : no appropriate default constructor available

Sample Code B
// custom.idl // MIDL options: #include   #include    #ifndef DO_NO_IMPORTS import "objidl.idl"; import "oleidl.idl"; import "oaidl.idl"; import "ocidl.idl"; #endif interface IB; [ object, uuid(27979FD1-E576-11cf-BFAC-00A02437A6A0) ] interface IA : IUnknown {      [propput, id(1)] HRESULT Interface([in] IB* pB); [propget, id(1)] HRESULT Interface([out, retval] IB** ppB); }  [ object, uuid(27979FD0-E576-11cf-BFAC-00A02437A6A0) ] interface IB : IUnknown {      [id(5)] HRESULT Method([in] int in1); }  [ uuid(596DBF82-2F2D-11D0-A537-00A02437A6A0), version(1.0) ] library Custom {      importlib(STDOLE_TLB); importlib(STDTYPE_TLB); interface IA; interface IB; }

// test.cpp // compile options: /GX /W4 /c #import "Custom.tlb" no_namespace class CA : IA  { STDMETHOD_(ULONG, AddRef) { return 0; } STDMETHOD_(ULONG, Release) { return 0; } STDMETHOD(QueryInterface)(REFIID, LPVOID* ) { return E_NOTIMPL; } // ICustom methods STDMETHOD(put_Interface)(IB *) { return E_NOTIMPL; } STDMETHOD(get_Interface)(IB **) { return E_NOTIMPL; } };  class CB   { CB{ CA* pA = new CA; if (pA) delete pA; }  };

Keywords: kbbug kbfix kbvs97sp1fix kbvs97sp2fix KB168009

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