Re: [boost] [BOOST_CLASS_EXPORT+export.hpp] multiple link error - gcc3.4

From: Robert Ramey (ramey_at_[hidden])
Date: 2007-06-28 11:46:14

I would recommend re-organizing the code slightly as below.

***TcpEndpoint.h***
 ...
// remove archive headers as they are not an attribute of the class 
TcpEndpint
 class TcpEndpoint : public I_Endpoint
 { ... };

 #include <boost/serialization/export.hpp>
 BOOST_CLASS_EXPORT_GUID(RCF::TcpEndpoint, "RCF::TcpEndpoint")

> ------------------------------------------------------
> ***a.cpp***
> ...
> #include "./TcpEndpoint.hpp"
> ...
> ------------------------------------------------------
> ***b.cpp***
> ...
> #include "./TcpEndpoint.hpp"
> ...
>
> ------------------------------------------------------
> ***c.cpp***
> ...
> #include "./TcpEndpoint.hpp"
> ...

> "A.h"
> #include <boost/serialization/export.hpp>
> class A : public Base {};
> BOOST_CLASS_EXPORT_GUID(A, "A")
>
....

 "main.cpp"

#include <boost/archive/text_oarchive.hpp>
 #include <boost/archive/text_iarchive.hpp>
#inlcude "A.h"
 #inlcude "B.h"
 #inlcude "C.h"

> int main() {...}

This should do it.   To summarize.

EXPORT should be considered an attribute of the class so it can/should be in 
the class header.

#include <...archive.hpp> is not an attribute of the class so it should NOT 
be in the class header.  It is used to emit code for each EXPORT ed type for 
each archive used.  So the combination of and exported type and and archive 
should be in one and only one module.  If you want to encapsulate the 
serialization code - e.g. you're making a library of all the code for all 
the types, make a module:

a.cpp

#include <boost/serialization/text_oarchive.hpp>
#include <boost/serialization/text_iarchive.hpp>
...// other archive types here.

#include "a.hpp" // includes EXPORT

template<class Archive>
void a:serialize(Archive ar, const unsigned int version){
    ar & ..;
    ....
}

Now you'll have the serialization code generated for type a and related to 
its export key.

Note that the code will be generated regardless of whether its called or 
not.  SOOOO
I would recommend that you organize your application as a library of 
modules.  One module
for each non-trivial type you use.  The then link your main module against 
the library.  This
will get you what you want, produce the smallest usable executables, and 
minimize compile
and link time.

Good Luck

Robert Ramey