Re: [Boost-users] [serialization] Difficulties with shared_ptr andexport.hpp

Deane Yang wrote:

First, I am trying to figure out how to use BOOST_CLASS_EXPORT. I am trying to do it using the following advice from the documentation:

"As noted in the comments, this would work. But #include <.../export.hpp> can't be used without conflicting with other modules which use #include <.../*archive.hpp>. In this case we can move the export to an implementation file:

Where did you find this in the documentation? I know its in there but I can't find it when I look for it in the HEAD.

// A.cpp #include "A.hpp" ... // export.hpp header should be last; #include ... BOOST_CLASS_EXPORT(A) ..."

In fact, my implementation file contains *only* BOOST_CLASS_EXPORT statements.

Then no code will be instantiated - as you have indeed found.

Code like this seems to compile only if I also include archive headers like: #include #include

correct.

If these directives are omitted, then my code does not compile.

Hmmm - the required code to export class x to archive xml_?archive.hpp will not be instantiated. I would expect that to show up as a missing symbol during linking.

Is this correct? (I didn't see anything about this in the documentation)

In the section: Exporting Class Serialization ... "we have described BOOST_CLASS_EXPORT. This is used to make the serialization library aware that code should be instantiated for serialization of a given class even though the class hasn't been otherwise referred to by the program. This functionality is necessary to implement serialization of pointers through a virtual base class pointer. That is, a polymorphic pointer." maybe that explanation should be made more complete. The usage of BOOST_CLASS_EXPORT will ensure that appropriate code to serialize the indicated type is generated for all archive types (and only those archive types) included when BOOST_CLASS_EXPORT is used.

But now if a class that is being exported contains a boost::shared_ptr<..> member (so I have to #include boost/serialization/shared_ptr.hpp), then I get the following compilation errors (in MSVC8.0express):

..\..\..\vendor\boost\boost/serialization/shared_ptr.hpp(134) : error C2039: 'reset' : is not a member of 'boost::archive::naked_xml_iarchive' ..\..\..\vendor\boost\boost/archive/xml_iarchive.hpp(91) : see declaration of 'boost::archive::naked_xml_iarchive' ..\..\..\vendor\boost\boost/serialization/split_free.hpp(58) : see reference to function template instantiation 'void boost::serialization::load(Archive &,boost::shared_ptr<T> &,const unsigned int)' being compiled

Can someone tell from this what I'm doing wrong?

Send me a little code that reproduces the problem. Robert Ramey