Thanks for all your help.
I have decided to try to reorganize everything into small parts as you have
said, in order to better understand.
I am in the process of
doing this, but I have already some remarks about your comments.
I have chosen the
organisation principle you have said:
in the class.h, nothing
about the serialization is present
in
serialization/class_serialization.hh : I have the serialization declaration
code + some traits
in
serialization/class_serialization.cc : I have the serialization implementation code
+ BOOST_EXPORT
The only thing where I
have not followed your advice is the presence of BOOST_EXPORT on the class_serialization.hh
rather than class_serialization.cc.
If I put it on the
header, since I have to include the header on test.cc, one instantation of
something is done while encountering BOOST_EXPORT. Later while compiling class_serialization.cc,
since it encounters BOOST_EXPORT one more time another instantiation occurs and
I had problems with linking (gcc 3.4 reported multiple definitions of
something).
I have attached a small
set of code that illustrates the problem. As the code is, it will fail to
compile (at least on gcc 3.4).
If you just remove
BOOST_EXPORT from MObject_serialization.hh and put it into MObject_serialization.cc,
everything works and the test passes.
I’d like to get
feedback on this – did I get everything right ??
Jean-Noël
Ps: I now even have a
clue about why the code failed in my old design, but I am waiting until I am
more sure of myself…
De :
boost-users-bounces@lists.boost.org
[mailto:boost-users-bounces@lists.boost.org] De
la part de Robert Ramey
Envoyé : jeudi 23 février
2006 17:44
À :
Objet : Re: [Boost-users]
Serialization : unregistered_cast & otherquestions
Without actually seeing the code, its hard for me to
give intelligent advice. Lucky for
you (maybe) that's not going to inhibit me from
speculating. Here is what I recommend
for anyone making a very large program:
a) extended_type_info_no_rtti presumes that all
classes serialized as pointers
have been exported. Should this not be the case,
you'll get the error message indicated.
Double check this.
b) Serilaization traits should be in the header files
so that they are not "missed" anytime
something like "ar << x" is invoked.
Given you're situation I would recommend a file
structure like the following:
class.hpp - without seriaiization like you have now.
serialization/class.hpp - includes class.hpp. also
includes BOOST_EXPORT and any
other traits for this "class".
serialization/class.cpp c - includes
serialization/class.hpp and includes the
actual serialization code. Also this should include
code instantiation for the archives that
you use. Look at demo_pimpl to see how this is done.
All the above code should be organized into a
library. The reason is that this will generate
code for all the archives mentioned but your
application may not use all the archives so
putting the above code in a library and linking to it
will mean that your application will
always have what it actuallyuses but nothing it
doesn't - avoids "code bloat". Note that
in compiling code for the library make sure to
specify "function level linking".
Take the "least derived class" - that one
at the top of the class hierarchy. Make a small
test program similar to the tests in the
serialization library. This should be a very small
job. This code can be class_test.cpp. Run this
test on all archives you use. When
this test passes, do the same for the other classes
until something fails.
This might seem to be more work - believe me its not.
It will
a) guarentee that you make progress toward a robust
program
b) give you confidence that your program has minimum
of hidden bugs
c) permit you to re-run the tests automatically when
you make future changes.
d) should a problem arise with the serialization or
other library, it will give
a lot more information in order to be helpful.
Robert Ramey