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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.windows.x
Subject: Re: Fixes to paint and xedit in V11.2
Message-ID: <24248@sun.uucp>
Date: Mon, 27-Jul-87 15:25:49 EDT
Article-I.D.: sun.24248
Posted: Mon Jul 27 15:25:49 1987
Date-Received: Tue, 28-Jul-87 07:32:17 EDT
References: <4477@jade.BERKELEY.EDU> <7439@diamond.BBN.COM>
Sender: news@sun.uucp
Lines: 26

> I fixed the toolkit by replacing all the calls to the various string
> functions with versions called XtStrCmp, XtStrCpy, etc. that handle
> NULL pointer arguments as would a VAX.

More correctly, as certain C and operating-system implementations do
on a VAX.  Unless the VMS versions of those routines waste time
checking for NULL arguments beforehand, they will blow up too, since
by default VMS does not map location 0 into a process' address space.

Furthermore, there are VAX UNIX implementations that permit you to
take location 0 out of a process' address space; the paging System V
implementations do, and John Bruner has made changes to 4BSD to
permit it to as well.  If somebody wants to link their programs on
such a system with the "disallow null pointer references" option,
they're going to be screwed unless the toolkit is fixed.  Not only
that, but the Berkeley people may very well decide to make no-page-0
the default if they rewrite the VM system in some future release.

If the people doing X development intend to continue doing it on
VAXes running 4BSD, they are hereby advised to try to get a hold of
John Bruner's changes, put them into their OS, and link *all* their
programs with the "no page 0" option, and catch more of these
problems before the software goes out the door.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	s tr329idssh