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From: Michael D. Crawford (crawford_at_[hidden])
Date: 2005-11-02 17:50:38

Peter Dimov saved me from a collosal blunder by correcting my impression
that shared_ptr wasn't thread-safe. I've posted a revised draft here:

I hadn't previously understood that thread-safety is not an all or
nothing proposition, that is, that one can only guarantee that certain
kinds of simultaneous operations will work. My revised text points that
out and quotes the first paragraph of shared_ptr's doc on thread safety.

I *did* know that there are different degrees of exception safety, so I
compare thread-safety guarantees to that. When I cover exception safety
in a week or so I'll discuss what that means; sometimes for reasons of
performance or memory conservation, one must choose not to be completely

Sermon at the Soup Kitchen

It's going to be about three hours before I post the final section and
submit to Kuro5hin. My first try at "The Right Tool for the Job" in my
Kuro5hin diary was characterized by one K5 member as "Utterly
incomprehensible", and I realize now he's absolutely correct, so I need
to address that.

I'm going to add a small section to it that I think I'll call "Every
Engineer's Solemn Duty" that exhorts the reader to do the right thing
when his company plows ahead with a disastrous engineering decision,
even if one risks losing one's job, getting blacklisted, sued or even
imprisoned. I don't think most engineers ever spend much time thinking
about such things until they are suddenly faced with actually making the
awful decision to issue an ultimatum, as I did, or blow the whistle, as
I still might.

I'm lucky I only lost my job. Think of the poor Morton Thiokol engineer
who didn't trust his conscience when he knew the Space Shuttle's O-rings
had frozen. He settled for reporting the risk of explosion through
company channels, and trusted that Morton Thiokol would do the right
thing. By not raising Hell and going directly to NASA when he realized
the launch hadn't been canceled, he allowed seven people to lose their
lives, a billion dollar spacecraft to be destroyed, and the US space
program to be set back several years.

If I can find a good web page about it, I'm also going to mention the
Ford Pinto's exploding gas tank. It came out in a lawsuit that Ford's
engineers made a calculated decision to let the gas tank go ahead and
explode because they didn't think the cost of paying the inevitable
lawsuit damages would be as much as the added manufacturing costs of a
safer tank.

Before quitting it to run "Yoyodyne" full time, "Jack's" last job was
managing a team designing a novel, experimental new medical device, the
failure of which would doom the patient to certain death within minutes.
  I might send a link to "Sermon at the Soup Kitchen" to his
ex-employer, along with an explanation of just who Jack and Yoyodyne
really are.

And yes, I'm well aware that if Jack ever reads my sermons he might try
to drag me into court. At least I can sleep soundly at night. You
should see all the emails I *don't* post online.


Michael D. Crawford

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