Re: [boost] [serialization] BOOST_CLASS_EXPORT worries

From: Vladimir Prus (ghost_at_[hidden])
Date: 2005-07-08 00:41:24

Robert Ramey wrote:

>> Now assume that we don't have plugins and applications written by the
>> same developer, but just a shared library. Say, I want to write a
>> library for manipulating EBNF grammar and want to add serialization.
>> Client applications are not written by me at all. Now if that
>> application defines a new archive type, nothing will work. Not to
>> mention that I'm not happy with bloating my library with code for 5
>> archive types (binary, text, xml + wide variants of the latter two).
>>
> 
> For this we have the polymorphic_ archives.  Compile once with the
> polymorphic archive headers.  Now your code is compatible with all
> archives
> past and future.  At least that is my intent.  Is there some reason this
> doesn't work as intended?  Note that your serialization code contains code
> for only one archive - the polymorphic archive.  There is no instantiation
> of code for the other archive classes.  The only cost is a teensy bit of
> execution time as as archive calls are redirected through a vtable.

Exactly. Now consider that I have a .cpp file that has BOOST_CLASS_EXPORT. I
don't know what kinds of archives will be used to serialize classes defined
in .cpp. So, I need to *always* #include polymorphic_archive headers. If I
don't include polymorphic archive, I'd need to include all standard archive
types (again, I have no idea which archive type will be actually used), and
that will instantiate a lot of code.

Why not make include polymorphic_archive automatic? And make other archive
types resort to polymorphic_archive when no serialization for that archive
type was BOOST_CLASS_EXPORTED. As you say, the only cost is a "teensy bit
of execution time", in most cases users won't even notice, but the code
size will be reduced.

- Volodya