[TUHS] Unix stories

Nick Downing downing.nick at gmail.com
Sun Jan 1 16:48:24 AEST 2017

I can never emphasize enough how much damage it does to just get people in
on a contract and let them scribble all over the company's valuable IP.
Soon they are gone but the damage lives on making the real programmers'
lives very difficult. Luckily the thing that took the contract programmer
months to do can usually be redone by the real programmer in a day or two,
but if it's been released it takes careful planning and opportunism to get
all the breakage out of the system. This was my life when I worked on cash
registers since software was basically a pimple on the side of hardware, my
bosses didn't understand software (or worse, thought they understood it and
hence trivialized it) so this would happen a lot, the software was seen as
more of a vehicle to get the hardware where it needed to go, rather than an
end in itself. Working there and dealing with customer complaints and
overseeing the expansion of what was originally a few BASIC programs to
print a report of the day's transactions on the receipt printer... to a
thousands and thousands of lines of code so the cash registers could
participate in multiple networks, download software and price updates,
report on takings and performances of different categories, order stock,
track till balances etc etc etc... really taught me a MASSIVE respect for
code quality, I almost never meet anyone who cares as much about code
quality and careful analysis of the system's assumptions and invariants
(like the assumption about drivers modifying a process' s signal mask in
your example)... as I do.

I can remember a conversation I had with a new hire in my research group
later on (not cash registers this time)... this dude had a PhD and had
written a hugely successful open source package that is still standard
today for a lot of courses etc in our field... and was hired to rewrite
some similar stuff created by our research group that was a bit of a dogs
breakfast but nevertheless was in daily use and publicly disseminated. Well
I had hacked on this dude's code a lot and I hated it, way overcomplicated
and using a very awkward structure of millions of interdependent C++
templates and what-have-you. He showed me his progress after some months
and I showed him a competing implementation (very immature) that I had put
together in my summer holiday using Python. So I tried to sell him the idea
of doing it in Python and structuring it all for simplicity and
maintainability... he was not having it. I could see his code would rapidly
descend into a dogs breakfast as soon as it was used to solve any real
world problem, because he was repeating all the same mistakes as in his
open source package.

So fast forward 5 years or so and he has a useable system, it is in daily
use and is being publicly disseminated. It is not too bad, until one looks
under the hood. I used it as a module in one of my major research tools and
it is great that it's available, BUT, it falls over miserably when you
stray away from the normal standard use cases that his group have tested
and made to work by extensive layers of band-aid fixes, leaving the code in
an incomprehensible state. I would spend days debugging and then send him a
comprehensive report on my investigation including several proposals for
short and long term fixes, he was initially enthusiastic about this but
lately my reports get labelled "won't fix" with weak excuses about it being
outside the common use cases. "Can't fix" would be more accurate. In the
process of all this I looked at the changelogs for the releases. In the
past 3 years there were a couple of feature releases and about 30 bugfix
releases, each accompanied by a release note which just kind of casually
passes this off as no big deal and implies the code is approaching a
reliable state. Ha!!

By contrast in May/June this year I decided to enter my tool in a
competition run by my research group and open to outside entrants, I think
about 20 groups entered including 3 or 4 internal entries like mine. Well
my tool was far from perfect since I had embarked on a major rewrite of the
frontend some months earlier and it was hard to produce anything working at
all, let alone competition quality. Luckily I had help from the competition
organizer, since internal entries are not eligible for prizes he was happy
to alert me to any problems he found and let me submit fixes if it did not
mess up his schedule. Well he found quite a few issues and I fixed them and
ended up having the fastest and best tool in the competition even though it
was not eligible for prizes. But now to the point of the story: The
CHARACTER of the problems he found. So much do I care about code quality
that it turns out most of the problems amounted to basically an oversight,
a misplaced comma that was hard to see, a pointer violation that occurred
because a realloc had moved some data during the evaluation of an
expression, that sort of thing. The fix never required any significant
restructuring of the code, except in one case where it was basically caused
by my using that other broken software as a module and I had to work around
it. I am so happy that my basic asusumptions and algorithms turned out to
be robust, because this means that after some period of getting all the
typos and minor oversights out, I will have a tool that is close to perfect
despite its complexity and the things I still plan to refactor and rewrite.
The guys who do not understand code quality will never experience this.

cheers, Nick

On 01/01/2017 4:00 PM, "Larry McVoy" <lm at mcvoy.com> wrote:

> Inspired by:
> > Stephen Bourne after some time wrote a cron job that checked whether an
> > update in a binary also resulted in an updated man page and otherwise
> > removed the binary. This is why these programs have man pages.
> I want to tell a story about working at Sun.  I feel like I've sent this
> but I can't find it in my outbox.  If it's a repeat chalk it up to old
> age.
> I wanted to work there, they were the Bell Labs of the day, or as close
> as you could get.
> I got hired as a contractor through Lachman (anyone remember them?) to do
> POSIX conformance in SunOS (the 4.x stuff, not that Solaris crap that I
> hate).
> As such, I was frequently the last guy to touch any file in the kernel,
> my fingerprints were everywhere.  So when there was a panic, it was
> frequently laid at my doorstep.
> So here is how I got a pager and learned about source management.
> Sun had two guys, who will remain nameless, but they were known as
> "the SCSI twins".  These guys decided, based on feedback that "people
> can interrupt sun install", to go into the SCSI tape driver and disable
> SIGINT, in the driver.  The kernel model doesn't allow for drivers messing
> with your signal mask so on exit, sometimes, we would get a "panic: psig".
> Somehow, I sure was because of the POSIX stuff, I ended up debugging this
> panic.  It had nothing to with me, I'm not a driver person (I've written
> a few but I pretty much suck at them), but it landed in my lap.
> Once I figured it out (which was not easy, you had to hit ^C to trigger it
> so unless you did that, and who does that during an install) I tracked down
> the code to SCSI twins.
> No problem, everyone makes mistakes.  Oh, wait.  Over the next few months
> I'm tracking down more problems, that were blamed on me since I'm all over
> the kernel, but came from the twins.
> Suns integration machines were argon, radon, and krypton.  I wrote
> scripts, awk I think, that watched every update to the tree on all
> of those machines and if anything came from the SCSI twins the script
> paged me.
> That way I could go build and test that kernel and get ahead of the bugs.
> If I could fix up their bugs before the rest of the team saw it then I
> wouldn't get blamed for them.
> I wish I could have figured out something like Steve did that would have
> made them not screw up so much but this was the next best thing.  I
> actually
> got bad reviews because of their crap.  My boss at the time, Eli Lamb, just
> said "you are in kadb too much".
> --lm
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