Prev: std::vector error
Next: Who Know How To set Windows password without old one -- VC Or C#
From: Stephen Howe on 15 Dec 2009 15:02
Hi

Using VS2005 Professional

I have bog-standard Win32 DLL, and it has an export header file like so

#ifdef MOD_EXPORTS
#define MOD_API __declspec(dllexport)
#else
#define MOD_API __declspec(dllimport)
#endif

class MOD_API CObj1
{

private:
CObj2 m_Obj2;
};


Now CObj2 resides in a proper library file (not an import library but a real library)
Both the Win32 DLL and the proper library use the RTL in DLL form yet I am getting

warning C4251: 'CObj1::m_Obj2 : class 'CObj2' needs to have dll-interface to be used by clients of class 'CObj1'

How do I eliminate this warning correctly (I dont mean shut the compiler up with a pragma, but I do if the warning is spurious)?
For that matter, how do I give CObj2 a DLL interface?

Thanks

Stephen Howe
From: Igor Tandetnik on 15 Dec 2009 15:26
Stephen Howe <sjhoweATdialDOTpipexDOTcom> wrote:
> I have bog-standard Win32 DLL, and it has an export header file like
> so
>
> #ifdef MOD_EXPORTS
> #define MOD_API __declspec(dllexport)
> #else
> #define MOD_API __declspec(dllimport)
> #endif
>
> class MOD_API CObj1
> {
>
> private:
> CObj2 m_Obj2;
> };
>
>
> Now CObj2 resides in a proper library file (not an import library but
> a real library)
> Both the Win32 DLL and the proper library use the RTL in DLL form yet
> I am getting
>
> warning C4251: 'CObj1::m_Obj2 : class 'CObj2' needs to have
> dll-interface to be used by clients of class 'CObj1'
>
> How do I eliminate this warning correctly (I dont mean shut the
> compiler up with a pragma, but I do if the warning is spurious)? For
> that matter, how do I give CObj2 a DLL interface?

You give it a DLL interface the same way you gave it to CObj1:

class MOD_API CObj2 {...};

The compiler probably could have realized that m_Obj2 is private and inaccessible to clients of CObj1, but it doesn't. It assumes that, if a class is exported to a DLL, all its members' types should also be exported.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

From: Stephen Howe on 16 Dec 2009 06:50
>> How do I eliminate this warning correctly (I dont mean shut the
>> compiler up with a pragma, but I do if the warning is spurious)? For
>> that matter, how do I give CObj2 a DLL interface?
>
>You give it a DLL interface the same way you gave it to CObj1:
>
>class MOD_API CObj2 {...};
>
>The compiler probably could have realized that m_Obj2 is private and inaccessible to clients of CObj1, but it doesn't. It assumes that, if a class is exported to a DLL, all its members' types should also be exported.

So that means the warning is spurious Igor?
I hope MS updates the warning so it is issued under more restricted circumstances (i.e. when relevant)

The class is internal to the main class. It is actually a wrapper around FILE * (so that it if the destructor is called and the
file is still open, it is closed).

Thanks

Stephen Howe
From: Igor Tandetnik on 16 Dec 2009 08:07
Stephen Howe wrote:
>>> How do I eliminate this warning correctly (I dont mean shut the
>>> compiler up with a pragma, but I do if the warning is spurious)? For
>>> that matter, how do I give CObj2 a DLL interface?
>>
>> You give it a DLL interface the same way you gave it to CObj1:
>>
>> class MOD_API CObj2 {...};
>>
>> The compiler probably could have realized that m_Obj2 is private and inaccessible to clients of CObj1, but it doesn't. It
>> assumes that, if a class is exported to a DLL, all its members' types should also be exported.
>
> So that means the warning is spurious Igor?

If CObj2 is not accessible to external clients by any means, then yes it is.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925
 | 
Pages: 1
Prev: std::vector error
Next: Who Know How To set Windows password without old one -- VC Or C#