Re: Multiple inheritance virtual abstract method disambiguation

From:
xKubo <peter.kubini@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Mon, 15 Aug 2011 11:05:39 CST
Message-ID:
<64886fde-4e2e-4cff-9839-8454daf7d565@fv14g2000vbb.googlegroups.com>
On Aug 15, 5:59 am, Seungbeom Kim <musip...@bawi.org> wrote:

On 2011-08-13 19:45, xKubo wrote:

Or you can qualify the function call with the class name:

   x.ITest::Close();
   x.ITest2::Close();


Sorry, this will give link errors, unless ITest{,2}::Close() are
explicitly defined (despite they are pure virtual). I meant:

   x.XITest1::Close();
   x.XITest2::Close();

(based upon the code posted by Gerhard Menzl).
XITest{1,2}::Close() override ITest{,2}::Close(), respectively,
but they are not really meant to be overridden further.

The meaning of the x.ITest::Close() is to call ITest::Close explicitly
(not as a virtual method). I tried it and if I add implementation
of the pure virtual method ITest::Close() like this:

struct ITest
{
   virtual void Close() = 0
   {
           cout << "XX";
   }
};

your line calls this method regardless of the fact that it is
overriden in class X. I think this is in accordance with C++ standard.


Indeed. Except that you cannot add a definition to the declaration of
a pure virtual function like that; there's no syntax supporting such.
You should write:

struct ITest
{
        virtual void Close() = 0;

};

virtual void ITest::Close()
{
        cout << "XX";

}


Yes, you're right. Once again - VS non-standard behavior. Actually, I
got used to it, and frankly I'm a bit lazy to write the method
twice ;-) especially when writing pure virtual destructors. Weird,
that there ale already 2 cases, in which VS with disabled language
extensions doesn't conform. I thought it should make VS compiler
standard compliant, at least it could spit a warning that it is
nonstandard.

P.

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