multiple type_info objects for same class in dynamic library
toon.knapen@femtown.org
toon.knapen@femtown.org
Sun Oct 17 08:38:00 GMT 2004
Inside a dynamic library (which is actually an extension module of
python and thus loaded by means of the import command in python), I have
a Base and Derived class. In following code inside this library
1) Derived* d = new Derived ;
2) std::cout << &typeid(*d) << ":" << typid(*d).name()<<'\n';
3) std::cout << &typeid(Derived) << ":" << typid(Derived).name()<<'\n';
line 2 and 3 shows that the type_info objects obtained are different
although the 'name()' member function provide the exact same name.
I'm using gcc 3.2 and python 2.3.3, the executable is linked with the
'-E' option (although I'm not sure if this is relevant since the Derived
class is only known in dynamic libraries but not to the executable), the
-Bsymbolic option is not used when linking.
My question now is: how can I analyse what happens with the different
weak symbols corresponding to the type_info object of the Derived class?
Since line 2 and 3 print different addresses, there must be multiple
type_info objects in the loaded program for the Derived class. In
multiple libraries, I can see a weak symbol _ZTSDerived (using nm it has
the symbol type 'V'). But all libraries have this same weak symbol so
why does the loaded program end up with multiple of these symbols (since
I obtain multiple addresses)?
Any idea would be very much appreciated. Thanks in advance.
Toon Knapen
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