Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!husc6!rice!sun-spots-request
From: aarons%cogs.sussex.ac.uk@nsfnet-relay.ac.uk (Aaron Sloman)
Newsgroups: comp.sys.sun
Subject: Obscure SunOS bug
Keywords: SunOS
Message-ID: <6265.8904230228@csuna.cogs.susx.ac.uk>
Date: 5 May 89 23:24:29 GMT
Sender: usenet@rice.edu
Organization: Sun-Spots
Lines: 36
Approved: Sun-Spots@rice.edu
Original-Date: Sun, 23 Apr 89 03:28:59 BST
X-Sun-Spots-Digest: Volume 7, Issue 268, message 17 of 21

Some of us were finding that in certain circumstances running our Poplog
system on a Sun4 with SunOS4.0 produced "illegal instruction", and that
this could be cured either by defining an extra environment variable or by
using unsetenv to remove one. We thought it was a Poplog bug, till our
chief programmer, John Gibson, showed that the symptom could be produced
in C.

Here is his analysis:

The Poplog bug that Aaron was getting on csunb (illegal instruction) turns
out to be a OS bug on the Sun-4 (something to do with paging on the
stack).

The following little C program exhibits the bug, but to do so it must be
run from csh without ANY environment variables defined (i.e. login without
a .login and then "unsetenv" on all the standard ones so that "printenv"
prints nothing).

f7() { ; }
f6() { f7();}
f5() { f6();}
f4() { f5();}
f3() { f4();}
f2() { f3();}
f1() { f2();}

main() { char a[12112]; f1(); }

Aaron Sloman,
School of Cognitive and Computing Sciences,
Univ of Sussex, Brighton, BN1 9QN, England
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