Re: [Boost-users] [serialization] problem using BOOST_CLASS_EXPORT macro in a static library

10 Feb 2009

      BOOST_CLASS_EXPORT relies on global objects' constructors to register
the necessary types, however the C++ standard allows a compiler to
strip away such objects unless they are actually used.

The C++ standard guarantees that all global objects contained in a
compilation unit (a CPP file) are initialized by the time execution
enters a function from that compilation unit. So, if execution never
enters a function from that compilation unit, the compiler is allowed
to deadstrip it.

You have 2 options:

1) tinker with your code to trick the compiler into leaving in (not
deadstripping) the automatic BOOST_CLASS_EXPORT registration (which is
usually possible), or

2) register the classes explicitly (not automatic, but guaranteed to work)

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode

On Tue, Feb 10, 2009 at 9:19 AM, Renaud Lepere  wrote:
...
I have some problems with BOOST_CLASS_EXPORT macro, it
seems that this macro have no effect if i put it in
a separate .cpp file of a static library.
I have a simple class Element that contains a pointer to a
curve that can be of different types (geom2d.hpp).
struct Curve
{
   Curve() {};
   virtual ~Curve() {};
};
struct Line : public Curve
{
   Line(int y = 0): m_y(y) {};
   int m_y;
};
typedef boost::shared_ptr< Curve > CurvePtr;
struct Element
{
   Element(const CurvePtr & curve):
       m_curve(curve) {}
   boost::shared_ptr< Curve > m_curve;
};
I would like to be able to serialize Element, so i
wrote a serialize.hpp file (attached) containing code for
serializing those structures.
I also wrote export.cpp using
#include "geom2d.hpp"
#include 
#include 
#include "serialize.hpp"
#include 
#include <iostream>
BOOST_CLASS_EXPORT(Curve);
BOOST_CLASS_EXPORT(Line);
I put the export.cpp file in a library named geom2d,
but when trying to serialize my structures using something
(attached main.cpp).
CurvePtr c(new Line(10));
       const Element e(c);
       std::ofstream ofs("filename");
       {
           boost::archive::text_oarchive oa(ofs);
           oa << e;
       }
I received an exception "unregistered class". If i dont
put export.cpp in a library but in the same compilation unit
as main.cpp, the error disappear (visual studio 8.0 and 9.0).
What is the good way of doing this, should i wrote an export.hpp file
containing the macros and include this file in a .cpp of the main
compilation unit ?
Thanks,
Renaud
_______________________________________________
Boost-users mailing list
Boost-users@lists.boost.org
http://lists.boost.org/mailman/listinfo.cgi/boost-users