Re: Interfaces in C++

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 7 Oct 2008 04:37:29 -0700 (PDT)

Message-ID:

<25182dbe-bfd2-41b8-858d-a8d49eee1f8d@x41g2000hsb.googlegroups.com>

On Oct 7, 8:07 am, anon <a...@no.invalid> wrote:

Maik wrote:

On 6 Okt., 21:12, "A.Gallus" <u...@rz.uni-karlsruhe.de> wrote:

Bingo, that did the job, thx!

class A
{
virtual void myfunc() = 0;
};

class B : public A
{

You should consider to prefer
class B : public virtual A
to avoid being bitten by:
http://www.parashift.com/c++-faq-lite/multiple-inheritance.html#faq-25=

..8

which will most likely happen if one uses the interface pattern.

I think that is worse performance wise then just this:
class B : public A
At least thats what I read
here:http://www.agner.org/optimize/#optimize

Another site to avoid. If you have a performance problem,
measure and see. Until then, using virtual inheritance when
inheriting from an interface is probably a good idea; in
general, virtual inheritance should probably be the default.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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