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Date:	Fri, 24 Dec 2004 13:48:44 -0500
Message-Id:	<200412241848.iBOImiRM013524@envy.delorie.com>
From:	DJ Delorie <dj AT delorie DOT com>
To:	djgpp AT delorie DOT com
In-reply-to:	<KpSdnePxHo9G_VHcRVn-oQ@comcast.com> (message from Joe Wright on
	Fri, 24 Dec 2004 13:33:07 -0500)
Subject:	Re: CTYPE stuff for Eli or DJ
References:	<KpSdnePxHo9G_VHcRVn-oQ AT comcast DOT com>
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> 'Splain me Batman. In ctypes.ha we have the macro..
> 
>     #define isspace(c) (__dj_ctype_flags[(int)(c)+1] & __dj_ISSPACE)
> 
> __dj_ctype_flags is an array 257 of unsigned short.
> 
> What assumptions are you making about '(int)(c)+1' that might ensure 
> the required index range of 0..256 ?

The ANSI C specification requires that applications pass only unsigned
chars, or the value EOF, to the ctype functions.  Values that meet
those requirements will not exceed the ctype array boundary.  Values
outside those requirements indicate that your application is faulty.

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