Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!usc!snorkelwacker!spdcc!mirror!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: How to write an 8-bit clean program
Message-ID: <15945@haddock.ima.isc.com>
Date: 14 Feb 90 22:42:50 GMT
References: <1990Feb10.151053.16702@is.uu.no> <1990Feb11.012110.2338@utzoo.uucp>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 16

In article <1990Feb11.012110.2338@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes:
>Most of the time, cleanly-written code does not care.  Using chars as
>characters -- rather than small integers -- seldom runs into sign issues

The problem is that getc() and the <ctype.h> functions deal with a type which
should have been "char" but in fact is a certain subrange of "int", namely the
union of {EOF} and the values of "unsigned char".  Thus, even cleanly-written
code has to be sprinkled with casts to convert "plain char" to "unsigned char"
before handing it to "isprint()".  (I'm assuming ANSI C semantics here, so
there's no isascii() nonsense.)

Fixing this (by which I mean doing it *right*, not slapping on a backward-
compatible patch) would involve getting rid of the constant EOF entirely.  Of
course, it's too late to change it now.

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint