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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.sources.bugs
Subject: Re: Compress  error messages
Message-ID: <26845@sun.uucp>
Date: Sat, 29-Aug-87 03:42:45 EDT
Article-I.D.: sun.26845
Posted: Sat Aug 29 03:42:45 1987
Date-Received: Sun, 30-Aug-87 08:47:31 EDT
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> Most of the time I see this message seems to be the case where someone
> tries to port a program to something like microport system 5 which has
> no "sysexits.h".  They then run off to the closest vax runing BSD and
> swipe the file from there.  All well and file except that the maping of
> the error messages to the numeric codes passed as arguments to perror()
> are not the same in BSD as they are in microport.  Hence the bizare
> messages (fine debuging aid they make).
> 
> All of this is a theory based on having seen many an error message apear
> out of context on microport in programs that like compress and RCS were
> written originaly on BSD systems.

This theory requires a pretty impressive deductive leap to get from "I see
these messages on Microport systems but not BSD systems" to "it must be
"sysexits.h".  Unfortunately, that leap will drop you in a canyon; it's bogus
as hell.  The error codes in <sysexits.h> have NOTHING WHATSOEVER to do with
the system call error codes in <errno.h>.  <errno.h> is present on Microport
System V and any other system that 1) supports program development and 2) can
justifiably claim to be UNIX or derived therefrom.

Furthermore, most of those numeric codes are generated from *system library
routines*; this means that the values in the include files on *your* machine
are totally irrelevant - the only values that are relevant there are the ones
defined on the machine on which the system was built, and the chances are good
that this value did not change between the time "perror" was compiled and the
time the routine returning the error code was compiled.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com