Path: utzoo!attcan!uunet!husc6!cmcl2!brl-adm!umd5!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: trap causes longjmp botch
Keywords: command line argument, Cshell, trap, longjmp
Message-ID: <11933@mimsy.UUCP>
Date: 13 Jun 88 07:18:10 GMT
References: <497@slb-sdr.UUCP> <534@unh.UUCP> <11820@mimsy.UUCP> <502@philmds.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 22
Xref: utzoo comp.unix.questions:7540 comp.unix.wizards:9277

In article <502@philmds.UUCP> leo@philmds.UUCP (Leo de Wit) writes:
>    Used to [use trap 'action' 0] myself that way too ... until one
>day the sh (/bin/sh; the Bourne shell on an Ultrix machine) complained
>about a 'longjmp botch'; I don't remember if there was a core dump.

Unless it was otherwise disabled (file `core' in current directory
unwritable, `limit coredumpsize 0', etc), there was.

>    What is the problem with this trap?  [explanation deleted]

The problem is that there is a bug in the 4.2BSD /bin/sh such that
`trap 0' outside of a script sometimes causes a longjmp to a stack
context that is no longer around.  Most likely this bug has been around
since V7, but is only caught now that longjmp unwinds the stack and
aborts if the frame is gone.

The bug does not occur when the trap is inside a script.

The bug remains in the 4.3BSD /bin/sh.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris