Re: The Function Order in vtable

From:

=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?= <Erik-wikstrom@telia.com>

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comp.lang.c++.moderated

Date:

Sun, 31 Aug 2008 02:58:52 CST

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<LAduk.1926$U5.1204@newsb.telia.net>

On 2008-08-30 17:28, annamalai wrote:

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?

No, the C++ standard does not even guarantee that there is a vtable, the
standard just describes how things should work not how to implement it.
On the other hand I believe that the authors discusses the
implementation of their ideas in a modified version of g++ called
ConceptC++, so the inclusion of implementation details does not surprise me.

--
Erik Wikstr?m

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