Re: [Boost-users] [Serialization] Serialization of a class in a DLL

From: Cyril Picat (cpicat_at_[hidden])
Date: 2008-05-29 14:00:28

Ok, I thought that BOOST_CLASS_EXPORT will take care of instantiating it.
Actually isn't it what is explained in the doc in paragraph 'Exporting Class
Serialization'? I am a bit confused and sure I should dive into the
Boost.Serialization code to understand more what the macro is doing.

The problem with your solution is that I don't want to include any Boost header
in Example.hpp. So I have tried the solution from demo_pimpl but it still fail
to link with  vc 8.0 (there is a comment saying that it fails with vc 7.0)? Is
it expected?

So I have ended with forward declaring the archives I need in Example.hpp and it
works.
Though, I would rather but the explicit template instantiation in Example.cpp to
keep a clean implementation agnostic header. Is there any way to make this work
with VC ?

So if anybody is interested, the final Example.hpp is:

/////// Example.hpp
#if _MSC_VER > 1000
#pragma once
#endif

// Do NOT include any headers after this point
#if (defined(__COMPILING_Example_CPP__) && defined(WIN32))
#define _LIBSPEC __declspec(dllexport)
#define _EXPORT_TEMPLATE template _LIBSPEC
#else
#define _LIBSPEC
#define _EXPORT_TEMPLATE extern template _LIBSPEC
#endif

namespace boost
{
  namespace archive
  {
    class xml_oarchive;
    class xml_iarchive;
  };
};

class _LIBSPEC MyClass
{
 public:
  MyClass();
  
 private:                                                    
  friend class boost::serialization::access;
  
  template <class Archive>                                     
  void serialize(Archive & ar, const unsigned int version);
  
  std::string m_str;
  
};

_EXPORT_TEMPLATE void
MyClass::serialize<boost::archive::xml_oarchive>(boost::archive::xml_oarchive&
ar, const unsigned int version);
_EXPORT_TEMPLATE void
MyClass::serialize<boost::archive::xml_iarchive>(boost::archive::xml_iarchive&
ar, const unsigned int version);

anyway, thanks your your help and your prompt reply.

Cyril Picat

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Robert Ramey
Sent: Thursday, May 29, 2008 1:20 PM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Serialization] Serialization of a class in a DLL

In order for this to work, you have to explicitly instantiate the code in the
library/dll.  It will not be instantiated automatically as it is not called from
within the library.

For an example of this take a look at demo_pimple

Robert Ramey

Cyril Picat wrote:
> Hi everybody,
>
> I have just tried a simple example of a class serialization in a DLL 
> and did not manage to make it work. I have been using Boost 
> serialization since a while but until now I was putting all the 
> serialization code in the .hpp. By the way thanks Robert (and Boost) 
> for this great library.
>
> I am using MSVC 8.0 and Boost 1.34.1. I have tried the same with Boost 
> Serialization 1.36 (head of Boost) without any success.
>
> My test is the following. The class MyClass in declared in a DLL 
> boost-example.dll built from Example.cpp. A test program Example.t.cpp 
> linked with boost-example.dll try to serialize MyClass to an XML 
> archive.
>
> The files are the following:
>
> //////// Example.hpp
> #if _MSC_VER > 1000
> #pragma once
> #endif
>
> // Do NOT include any headers after this point #if
> (defined(__COMPILING_Example_CPP__) && defined(WIN32)) #define 
> _LIBSPEC __declspec(dllexport) #else #define _LIBSPEC #endif
>
> class _LIBSPEC MyClass
> {
> public:
>  MyClass();
>
> private:
>  friend class boost::serialization::access;
>
>  template <class Archive>
>  void serialize(Archive & ar, const unsigned int version);
>
>  std::string m_str;
>
> };

// add the folloing here

#include <boost/archive/xml_oarchive.hpp>

#include <boost/archive/xml_iarchive.hpp> ....

// instanciate the code we want to generate and add tothe library template
MyClass::serialize<boost::archive::xml_oarchive>;

template MyClass::serialize<boost::archive::xml_iarchive>;

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