Trouble with deriving from boost::archive

4 Oct 2005

      I posted this earlier, but I don't think it went through all the way.  I
apologize if this is a duplicate:

------------------------------------------------------------------------
--------------------

Hi All,
  Boost newbie here:  I am having problems with getting serialization to
work
with my app.  I have a top-level "environment" context that objects in
my app
need to be associated with.  I thought about various ways to accomplish
this 
and I thought the best way might be to derive an Archive class that
maintains a
reference to the context and use custom
save_construct_data/load_construct_data
overrides.

However, I am hitting a snag and I don't quite understand what is
happening.  I
derive an input and output archive from text_iarchive/text_oarchive 
respectively and I use this archive context.  However I get the
following 
error in compilation:

db.hh: In function `void
boost::serialization::load_construct_data(Archive&, 
   FlatFileDb::Db*, unsigned int) [with Archive = 
   boost::archive::text_iarchive]':
/ccase/cca/vendor/boost/boost/serialization/serialization.hpp:170:  
instantiated from `void
boost::serialization::load_construct_data_adl(Archive&,
 T*, unsigned int) 
[with Archive = boost::archive::text_iarchive, T = FlatFileDb::Db]'
/ccase/cca/vendor/boost/boost/archive/detail/iserializer.hpp:303:
instantiated
from `void boost::archive::detail::pointer_iserializer::load_object_ptr(boost::archive::detail::basic_iarchive&,
void*&,
unsigned int) const [with T = FlatFileDb::Db, Archive =
boost::archive::text_iarchive]'
/ccase/cca/vendor/boost/boost/archive/detail/iserializer.hpp:209:   
instantiated from here
db.hh:84: error: 'class boost::archive::text_iarchive' has no member
named '
   m_env'

Somehow the system is assigning <class Archive> to 'class
boost::archive::text_iarchive' even though I am creating the archive as
something derived from text_iarchive.  The weird thing is that this
happens 
even if I comment out the code the invokes the actual archiving.  Its
almost 
like there is some default value of Archive that gets assigned once I
include 
the text_iarchive.hpp file.  Any ideas on how to stop this from
happening?  
Is there a better way to accomplish my goal?

Thanks in advance!
-Greg

PS: Here are some code snippets of what I am doing.

I have a header file called "archive.hh" with

-----------------------------------------------------------

#include 
#include 

namespace FlatFileDb
{
    class Env;

    class OArchive : public boost::archive::text_oarchive_impl<OArchive>
    {
    public:

        OArchive(Env &env, std::ostream & os, unsigned int flags = 0) :
            boost::archive::text_oarchive_impl<OArchive>(os, flags),
m_env(env)
            {}
        ~OArchive(){} 

        Env &m_env;
    };  

    class IArchive : public boost::archive::text_iarchive_impl<IArchive>
    {
    public:

        IArchive(Env &env, std::istream & is, unsigned int flags = 0) :
            boost::archive::text_iarchive_impl<IArchive>(is, flags),
m_env(env)
            {}
        ~IArchive(){} 

        Env &m_env;
    };
};

--------------------------------------------------

and then I have another header file (db.hh) with:

--------------------------------------------------

<.../snip...>

namespace boost { namespace serialization {
template<class Archive>
inline void save_construct_data(
    Archive & ar, const FlatFileDb::Db *t, const unsigned int
file_version
){
    // save data required to construct instance
    ar << t->m_name;
}

template<class Archive>
inline void load_construct_data(
    Archive & ar, FlatFileDb::Db* t, const unsigned int file_version
){
    // retrieve data from archive required to construct new instance
    std::string name;
    ar >> name;
    // invoke inplace constructor to initialize instance of my_class
    ::new(t)FlatFileDb::Db(ar.m_env, name);  <-- !!! blows up here !!!y
}
}} // namespace ...

Haskins, Gregory

Robert Ramey

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