From: Jeff Garland (jeff_at_[hidden])
Date: 2007-05-04 20:11:55
Hartmut Kaiser wrote:
> Stefan,
>
>> Appologies from me, too, as now we are getting even further
>> from the original topic.
>>
>> I have seen at least one case where it was indeed X.hpp that
>> introduced the dependency to serialization code. However,
>> this generates another
>> problem:
>>
>> 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.
>
> I'm not sure, if this is always possible.
This isn't a new debate, but I believe a separate user specified header is the
correct solution. This is how date-time is done and others should be as well.
As I recall prior discussions, not all libraries have been factored that way
-- I think multi-index isn't -- Joaquin had some good reasons. Anyway, it's a
bit more effort, but because of the serialization design it should always be
possible do have external serialization functions. In general serialization
requires a pile of extra includes that should be avoided if possible.
>> PS: the library I'm thinking of is boost.wave, and there serialization
>> was dragged in whenever BOOST_WAVE_SERIALIZATION is defined.
>
> As far as Wave is concerned, the mentioned macro has no influence on the
> code generated for the library. You always can define
> BOOST_WAVE_SERIALIZATION to zero when compiling your code, even if the
> library was compiled with BOOST_WAVE_SERIALIZATION=1. The generated library
> has no dependency on Boost.Serialization.
Seems to me that unless it's essential to library function serialization
support should always be turned off by default.
Jeff