Re: [Boost-users] Serialization: docs regarding abstract base class

From: Robert Ramey (ramey_at_[hidden])
Date: 2006-03-01 21:48:30

Note that the tutorial programs do use BOOST_IS_ABSTRACT so I've always 
assumed that
it functions as advertised.  Since the demo doesn't use BOOST_EXPORT, I 
suspect that
that there is some sort of problem related to instantiation of abstract base 
class code
for exported types.  I'lll look into it.

Robert Ramey

"RIVASSEAU Jean Noel" <JN.RIVASSEAU_at_[hidden]> wrote in message 
news:87F60F7FA02FF749AFB02BD9FCAA6B04DE1BE3_at_naserv31.nanterre.oberthurcs.com...
I quote the Boost serialization docs:

When serializing an object through a pointer to its base class and that base 
class is abstract (i.e. has at least one virtual function assigned a value 
of 0), A compile error will be emitted. This is addressable in one over 
several ways:
remove the =0 in the base classes so that the base class is no longer 
abstract.
implement is_abstract for your compiler. (code written according to the C++ 
standard is included with this library. But it is known to fail on several 
compilers.

If the compiler suports "is_abstract" type trait - use that.
Otherwise assume a class is NOT abstract
unless BOOST_IS_ABSTRACT has been set for the class.
use the macro BOOST_IS_ABSTRACT(my_class) to indicate that the class is an 
abstract base class. This will cause the compiler to avoid generating code 
that causes this error.
I still do not understand part 2 of this advice, Robert. Could you explain?

Jean-Noël

Ps: as already mentioned, part 3 does not change anything for me, and I'd 
like to avoid the solution of part 1 since I do want the base class to be 
abstract.

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