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Date: Sat, 09 Oct 2004 07:05:00 -0000
From: Jamie Lokier <jamie@shareable.org>
To: Joe Buck <Joe.Buck@synopsys.COM>, Nick Ing-Simmons <nick@ing-simmons.net>,
   gcc@gcc.gnu.org, "'Morten Welinder'" <terra@gnome.org>,
   Dave Korn <dk@artimi.com>
Subject: Re: signed vs unsigned pointer warning
Message-ID: <20041008205912.GA16038@mail.shareable.org>
References: <20040922161751.B4F6A1422D53@darter.rentec.com> <NUTMEGODkUqESudbgsy00000021@NUTMEG.CAM.ARTIMI.COM> <20040926192142.GA29842@mail.shareable.org> <20040926192142.GA29842@mail.shareable.org> <20041008130623.9516.4@llama.elixent.com> <20041008091714.A1695@synopsys.com> <m3d5zttbu6.fsf@multivac.cwru.edu> <20041008100853.A2207@synopsys.com> <m3mzyxgkil.fsf@multivac.cwru.edu>
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Paul Jarc wrote:
> > No, (unsigned)-1 does not turn into 255, it turns into a very large
> > number.
> 
> But character 255, as a signed char, is also -1, and so will also
> become the same large number.  The caller must cast char to unsigned
> char to ensure that EOF is distinct.  *Only* the caller can make the
> distinction reliably, since only the caller knows whether this
> particular -1 is supposed to be EOF.

Is it necessary for them to be distinct?

I didn't see any rule in "man isalpha" saying anything about EOF
other than it's accepted as an argument value.

In particular, is it ok if isalpha(EOF) == isalpha(255), whatever the
value of isalpha(255)?

Or is there a rule that is*(EOF) must return 0?

-- Jamie