Re: [boost] library dependencies

From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2007-05-04 15:02:35

> Emil Dotchevski wrote:
>>  If X is usable without serialization, users shouldn't be forced to also
>>> link to the serialization library, just because of this dependency.
>>> (In the particular case I have in mind this dependency was controlled
>>> by a preprocessor macro. That's not very practical, since packagers
>>> surely won't provide two sets of packages for X, one with and one 
>>> without
>>> this dependency.)
>>>
>>> Thus, I'd suggest to encapsulate the X-serialization functionality into
>>> a separate library (may be header-only), such as X_serialization.hpp
>>> etc. Then I can still use X stand-alone, and drag in the rest whenever
>>> I need it.
>>
>> This has been discussed before. You don't need X_serialization.hpp, if 
>> you
>> don't use BOOST_CLASS_EXPORT. See
>> http://www.archivesat.com/Boost_developers/thread2900871.htm.
>
> I'm not sure how relevant that is. If X.hpp contains serialization-related
> code, it surely needs to include serialization header files, too, to drag
> in any relevant declarations. Thus there is a dependency from X to 
> serialization.

You need no declarations because the serialization is implemented as a 
function template:

class foo;

template<class Archive>
void serialize(Archive & ar, foo & x, const unsigned int version)
{
    ar & x.bar;
    ....
}

The above code compiles without including any boost serialization headers.

I have not used boost serialization (I have my own serialization library), 
but as far as I can see the reason why foo.hpp that uses boost serailization 
needs to include serialization headers, is to be able to use 
BOOST_CLASS_EXPORT. For me this is good enough reason not to use 
BOOST_CLASS_EXPORT.

Emil Dotchevski