Re: The Function Order in vtable
annamalai ha scritto:
Hi. I have been going through the following article (titled, "Runtime
Polymorphic Generic Programming?Mixing Objects and Concepts in ConceptC
++") on the poly<> library.
http://homepages.fh-regensburg.de/~mpool/mpool07/proceedings/5.pdf
In section 3.2 "Refinement", the authors are explaining about the use
of dynamic_cast to determine the most refined concept the particular
object models. During this explanation they mention the following:
(begin-quote)
For example, PlaceableHandle?s place() operation is implemented in
terms of PlaceableInterface by jumping to the fourth entry in the
vtable.
(end-quote)
This suggests that there is a specific guaranteed order in which the
member functions can be accessed via the vtable. Is this guaranteed
by the C++ language? And is the order based on the name of the member
function or the order of declaration? Can anybody explain this
further to me?
The C++ language does not even guarantee that virtual functions are
implemented using a vtable, so definitely a specific order is *not*
guaranteed! The use of reinterpret_cast<> makes the code in section 3.2
implementation-specific. It's very strange to see such a low-level trick
used together with concepts, which are inherently a high-level construct...
HTH,
Ganesh
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