Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!ucbcad!ucbvax!cbosgd!clyde!watmath!rbutterworth
From: rbutterworth@watmath.waterloo.edu (Ray Butterworth)
Newsgroups: comp.lang.c
Subject: Re: Ansi C -- no system-specific pre-#defines
Message-ID: <16050@watmath.waterloo.edu>
Date: 29 Dec 87 14:52:50 GMT
References: <8712260015.AA01517@decwrl.dec.com>
Organization: U of Waterloo, Ontario
Lines: 19

In article <8712260015.AA01517@decwrl.dec.com>, minow@thundr.dec.com (Martin Minow THUNDR::MINOW ML3-5/U26 223-9922) writes:
> In a recent posting, watmath!rbutterworth suggests that noalias could
> be replaced by a compiler-specific _noalias keyword and a user writing
> portable code should addd something like
>   #if !defined(_XYZ_COMPILER)
>   #   define _noalias /*nothing*/
>   #endif
> Unfortunately, the Ansi committee doesn't seem to allow vendor-specific
> pre-defined variables.  I asked specifically for this in my comments
> to the November '86 Draft Standard and was rejected.  The August '87
> Draft (section 3.8.8) seems somewhat ambiguous in this matter, however.

What am I missing?
The standard allows the compiler and library maintainers to use
any names they like as long as they begin with a leading underscore.
User code that uses such leading underscore names is of course non-
portable, but in this case it can easily be made portable by the
above #define.  And all ANSI standard code willl still compile
correctly on this compiler since it is guaranteed not to contain
the identifier _noalias.