Re: [boost] warning C4275 with VC++ (non dll-interface class...) (again)

From: Luke Elliott (luke_elliott_at_[hidden])
Date: 2005-08-24 11:17:27

Nigel Stewart wrote:
>>>>>However, the warnings can be removed by exporting only members which 
>>>>>truly need to be exported
> 
> 
>>>>	I would be a bit reluctant about "pollution"
> 
> 
>>>Have you seen the boost header files?!  :)
> 
> 
>>There are some other benefits: smaller binaries, the optimizer seems to 
>>do a better job...
> 
> 
> Sounds interesting, any further information available?
> 
> Nigel

Whoops! Try again...

With:

class MY_LIB_API my_class
{
public:
        void some_fn();

        void some_inline_fn()
        {
                ++m_i;
        }

        int get()
        {
                return m_i;
        }

private:
        int	m_i;
};

dumpbin /exports exports.dll

Microsoft (R) COFF/PE Dumper Version 7.10.3077
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file exports.dll

File Type: DLL

   Section contains the following exports for exports.dll

     00000000 characteristics
     430C9B5E time date stamp Wed Aug 24 11:07:58 2005
         0.00 version
            1 ordinal base
            4 number of functions
            4 number of names

     ordinal hint RVA      name

           1    0 00001020 ??4my_class@@QAEAAV0_at_ABV0@@Z
           2    1 00001010 ?get_at_my_class@@QAEHXZ
           3    2 00001000 ?some_fn_at_my_class@@QAEXXZ
           4    3 00001000 ?some_inline_fn_at_my_class@@QAEXXZ

So the "inline" functions are actually exported from the dll. Whereas:

class my_class
{
public:
        MY_LIB_API void some_fn();

        void some_inline_fn()
        {
                ++m_i;
        }

        int get()
        {
                return m_i;
        }

private:
        int	m_i;
};

dumpbin /exports exports.dll
Microsoft (R) COFF/PE Dumper Version 7.10.3077
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file exports.dll

File Type: DLL

   Section contains the following exports for exports.dll

     00000000 characteristics
     430C9BA8 time date stamp Wed Aug 24 11:09:12 2005
         0.00 version
            1 ordinal base
            1 number of functions
            1 number of names

     ordinal hint RVA      name

           1    0 00001000 ?some_fn_at_my_class@@QAEXXZ

You only get the explicitly exported methods. All makes sense, I suppose.

As far as optimizations go, I've seen that a client of a dll may not use 
an inline method and may make an actual dll call if the inline method is 
declspeced. I just tried that with a simple example and of course 
couldn't demonstrate it...

Luke.