Re: [Boost-users] [Serialization] 1.33 RC1 nvp.hpp gotcha

From: Richard Jennings (Richard.Jennings_at_[hidden])
Date: 2005-08-10 04:00:20

I am a bit baffled why you can get the example to compile!  I can't try
it on VC7.1 today, though I will tomorrow, however I can't see anything
compiler specific about it:

Serialization/nvp.hpp includes serialization/traits.hpp that defines
BOOST_SERIALIZATION_TRAITS_HPP.
Serialization/vector.hpp includes collections_save_imp.hpp that includes
archive/basic_archive.hpp that checks for BOOST_SERIALIZATION_TRAITS_HPP
being defined and thereby says #error.

Therefore it appears that whenever vector.hpp is included after nvp.hpp
that basic_archive will choke.

BTW When I said that perhaps it only worked by luck before I meant that
my application worked by luck as I was not overly careful about header
inclusion order or what went in the precompiled headers and what didn't.
I did _not_ mean that it's lucky the serialization library works!  I
have found it very simple to use and very powerful.

Richard

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Robert Ramey
Sent: 09 August 2005 17:11
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Serialization] 1.33 RC1 nvp.hpp gotcha

Richard Jennings wrote:
> I have found that the requirement that no serialization headers can be

> included before any archive headers means that you have to be careful 
> which serialization headers you include in your class headers and 
> indeed in what order you include them.

It is my intention that this issue be addressed with the simple rule:

"all headers from the serialization directory should follow and headers
from the archive directory"

I believe that this rule should be very easy to follow.

As a beneficial side-effect of flagging any usage of "archive" headers
in include modules for classes.  This would accidently link a
serialization definition with implementation of a specific archive.

>
> In particular if you include serialization/nvp.hpp before
> serialization/vector.hpp and you use that class in another module that
> does not use archiving at all then that module will hit the error
> directive, example below.

This would surprise me. Your example looks good to me.  So I built on my
own 
machine.  Both main.cpp and B.cpp compiled without problems with VC 7.1
. 
So we're out of sync somehow.

> A solution would seem to be that serialization/nvp.hpp should only be
> included in the module that includes archive headers.

This wouldn't work and shouldn't be necessary.  Lets beat upon your
example 
some more until we get the same results.

> I guess what I would like is some guidance on using serialization as
> it's become a bit more tricky in my experience.

I would hope that its not too tricky.  The system is designed to be as 
tricky as necessary - but no trickier.

> At least you can't willy-nilly include serialization headers in any
order 
> in any headers
> and expect the application to compile.

True

>Perhaps it only worked by luck before!

LOL - well I do consider myself a lucky person !!! But

A very small observation on your code:

#include <vector> // note this is superflous - but harmless
#include <boost/serialization/vector.hpp> // as the above is included by

this module

Robert Ramey

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