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From: guy@rlgvax.UUCP (Guy Harris)
Newsgroups: net.unix-wizards
Subject: Re:  4.2 signals broken?
Message-ID: <1470@rlgvax.UUCP>
Date: Mon, 12-Dec-83 20:05:57 EST
Article-I.D.: rlgvax.1470
Posted: Mon Dec 12 20:05:57 1983
Date-Received: Thu, 15-Dec-83 01:48:07 EST
References: <14475@sri-arpa.UUCP> <1126@pur-phy.UUCP>
Organization: CCI Office Systems Group, Reston, VA
Lines: 23


	I don't have access to a System III/V machine, so correct me if I'm
	wrong, but isn't Sys III/V non-backward compatible to V7?  The tty
	driver, the fcntl() call, and changing the names of some library
	routines comes to mind (index, rindex, strn???).  Is it possible to
	completely emulate V7 behavior in Sys III/V?  If not, then what 4.2
	did to signals seems to be analogous.

Yes, S3/S5 are not 100% backward compatible with V7, but are about 98-99%
backward compatible.  Most of the changes needed to make V7 programs run on
S3/S5 or vice versa are trivial ("index" <-> "strchr" and "rindex" <-> "strrchr"
are commonly done with #defines or -Dindex=strchr; "strn???" didn't change
between V7 and S3 - it changed between some VERY old versions of UNIX and V7/
UNIX/TS 1.0, which changed "strcpyn" and the like to "strncpy").  However,
completely emulating V7/4.1BSD/S3/S5/... signals under 4.2BSD is trickier
(although note that if you used the "-ljobs" library under 4.1BSD "read",
"write", and "wait" got restarted like they do under 4.2); the "easiest" way
is probably to grab the code used by the binary compatibility with 4.1
feature, which turns on a "using old signal mechanism" bit, and use that.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy