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From: peter@sugar.UUCP (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: Does ANSI C have lengthof() ?
Message-ID: <662@sugar.UUCP>
Date: Sun, 6-Sep-87 09:05:05 EDT
Article-I.D.: sugar.662
Posted: Sun Sep  6 09:05:05 1987
Date-Received: Wed, 9-Sep-87 05:45:31 EDT
References: <9154@brl-adm.ARPA> <1265@mhres.mh.nl>
Organization: Sugar Land UNIX - Houston, TX
Lines: 37

> I think there is more need for these functions in the pre-processor:
> 
>     # if sizeof (char*) == sizeof (int)
>     typedef int numptr;
>     # else
>     # if sizeof (char*) == sizeof (long)
>     typedef long numptr;
>     # endif
>     # endif
>     # if unknown (typeof (numptr))
>     .... error ....
>     # endif

Well, first of all the preprocessor doesn't know the first thing about
typedef, other than it's a character string it's copying and ignoring.
The preprocessor doesn't know a type from a keyword. It probably doesn't
know from sizeof, either... it only knows about constants that have been
defined to it with #define. Even if it knows sizeof(int), it shouldn't
know about (for example) sizeof(numptr) or sizeof(struct foo).

Secondly:

     # if sizeof (char*) == sizeof (int)
     #  define NUMPTR int
     # else
     # if sizeof (char*) == sizeof (long)
     #  define NUMPTR long
     # endif
     # endif
     # if !defined(NUMPTR)
     .... error ....
     # endif

Finally, I do think typeof would be a great addition to the language.
-- 
-- Peter da Silva `-_-' ...!seismo!soma!uhnix1!sugar!peter
--                 'U`  <-- Public domain wolf.