Re: [Boost-users] [Serialisation] Question on shared_ptr'sand base/derived classes

From: Hughes, James (jhughes_at_[hidden])
Date: 2007-05-02 09:00:59

I checked, the base did not have a virtual destructor (I didn't write
it!!), but even adding that, the code still bus errors.

Is there anything specific I need to add for serialisation of shared_ptr
and derived classes? Currently I just have the serialise functions in
all the classes being serialised. I already call the base class
serialisation using base_obect in the derived classes serialize
functions, but I haven't added the BOOST_CLASS_EXPORT_GUID stuff
referred to in certain parts of the docs as I thought that it should
work without it - reason being it doesn't throw unregistered_class, it
bus errors.

Strangely, I have now tried to use the BOOST_CLASS_EXPORT_GUID macros in
the derived class, and they cause a compile fault along the lines of...

BOOST_CLASS_EXPORT_GUID(LCTextPanel, "TextPanel");

causes

>>whole load of template faults I don't understand then...
../boost_1_33_1/boost/archive/basic_xml_archive.hpp:66: error :
incomplete type 'boost::STATIC_ASSERTION_FAILURE< false>' used in nested
name specifier
../boost_1_33_1/boost/archive/basic_xml_archive.hpp:66: error : size of
array has non-integral type '<type error>'

So if anyone knows what that means as it might be what's causing the
other issue....??

James

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of Richard Damon
Sent: 02 May 2007 12:19
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Serialisation] Question on shared_ptr'sand
base/derived classes

One comment is that:

Class A {
}; // No virtual destructor

Class B : public A {
}

shared_ptr<A>(new B)

Should cause UB as the shared pointer will will eventually call delete
on its parameter, and since A has no virtual destructor and is NOT the
type the object was created with, you get UB.

It basically boils down to the equivalent to this

A* ptr = new B;
delete ptr;

which is a no-no.

A NEEDS to have a virtual destructor to use it the way you are.
Richard

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