Re: Stack size limit?

2002-09-12 Thread David Kastrup 

   Date: Wed, 11 Sep 2002 18:58:39 +0200
   From: Thomas Esser [EMAIL PROTECTED]

I found that the following ditty which in earlier incarnations of my
system just died almost immediately with a Segmentation Fault, will
under current 2.4 Linux kernels under, say, RedHat's (null) beta,
cause the machine to more or less freeze:

tex '\def~{\if~}~'

   My system (linux with 2.4.19 kernel) get slower, but tex is stopped with
 ! TeX capacity exceeded, sorry [main memory size=251].
   after a few seconds.

Which is very much harmless, no issue with that.  For small settings
of the stack ulimit, this might also have segfaulted fast, what I
experienced previously and with which I don't have a problem, either.
But if you write \number instead of \if you should get to see the
unmitigated original problem, as I checked now.  Please pass this on
to the web2c maintainer, I had just reported this from memory, and \if
seems to have another brake built in.  With \number, on _this_ system
(not the one I am writing this mail on, logged in there remotely), the
Linux OOM killer got active and pulled the plug on the TeX process --
good decision.  But it might also have decided to pull the plug on the
X Server instead.  This will not cause any problem unless the stack
size ulimit is rather large or unlimited, which unfortunately seems to
be the default on my Laptop (newest RedHat).

That's bad.  So perhaps one should let TeX automatically set a stack
size limit, roughly what
ulimit -s 1024 or so would do.

   There are always ways to do weired things and to bring the system down
   unless you set up limits that make the system unusable.  I don't think
   that adding such a system dependency is worth the trouble.

Well, I would consider it worth the trouble in cases where this may
affect system stability.

   Anyway, the maintainer of web2c should decide that (since I aim to
   follow him as closely as possible), so I'll forward him your
   request.

I agree.  Please pass on this letter as well, if it is not too much
trouble and if he is not reading the pretest list.

-- 
David Kastrup Phone: +49-234-32-25570
Email: [EMAIL PROTECTED]   Fax: +49-234-32-14209
Institut für Neuroinformatik, Universitätsstr. 150, 44780 Bochum, Germany

Re: Stack size limit?

2002-09-12 Thread Paul Vojta 

 Date: Thu, 12 Sep 2002 11:41:30 +0200 (MEST)
 From: David Kastrup [EMAIL PROTECTED]
 To: [EMAIL PROTECTED]
 Subject: Re: Stack size limit?
 
There are always ways to do weired things and to bring the system down
unless you set up limits that make the system unusable.  I don't think
that adding such a system dependency is worth the trouble.
 
 Well, I would consider it worth the trouble in cases where this may
 affect system stability.

If TeX can bring down the operating system, then it's a bug in the O/S,
not in TeX.

--Paul Vojta, [EMAIL PROTECTED]

Re: Stack size limit?

2002-09-11 Thread Thomas Esser 

Dear David,

 I found that the following ditty which in earlier incarnations of my
 system just died almost immediately with a Segmentation Fault, will
 under current 2.4 Linux kernels under, say, RedHat's (null) beta,
 cause the machine to more or less freeze:
 
 tex '\def~{\if~}~'

My system (linux with 2.4.19 kernel) get slower, but tex is stopped with
  ! TeX capacity exceeded, sorry [main memory size=251].
after a few seconds.

 That's bad.  So perhaps one should let TeX automatically set a stack
 size limit, roughly what
 ulimit -s 1024 or so would do.

There are always ways to do weired things and to bring the system down
unless you set up limits that make the system unusable. I don't think
that adding such a system dependency is worth the trouble. Anyway,
the maintainer of web2c should decide that (since I aim to follow him
as closely as possible), so I'll forward him your request.

Thomas