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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: constant expression rules
Message-ID: <6471@brl-smoke.ARPA>
Date: Sat, 26-Sep-87 23:00:28 EDT
Article-I.D.: brl-smok.6471
Posted: Sat Sep 26 23:00:28 1987
Date-Received: Sun, 27-Sep-87 11:58:27 EDT
References: <3018@ulysses.homer.nj.att.com>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 11
Keywords: portability

In article <3018@ulysses.homer.nj.att.com> ggs@ulysses.homer.nj.att.com (Griff Smith) writes:
>The question is - what is a reasonable level of constant folding that
>I can assume when trying to write portable code?

The practical answer is, if you need to anticipate the actual behavior
of a wide range of existing C compilers, you cannot count on very much!
Generally, constant expressions involving just integers and the simple
arithmetic operations are handled correctly by C compilers.  Constant
expressions involving much more, for example floating-point and casts,
are only handled correctly by some implementations, although the
forthcoming C standard promises that they are valid in initializers.