Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c++
Subject: Re: Ansi C compatibility
Message-ID: <6961@brl-smoke.ARPA>
Date: 6 Jan 88 09:42:41 GMT
References: <590@PT.CS.CMU.EDU>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 19

In article <590@PT.CS.CMU.EDU> dld@F.GP.CS.CMU.EDU (David Detlefs) writes:
>We're operating under the assumption that any ANSI-C compiler will
>define "_ansi_c_", and will modify any of those (as well as CC)
>locally to do this.  Does anyone have a better idea?

Yes, how about using the symbol __STDC__ that an ANSI C implementation
is required to provide a predefinition for?

>P.S.  Can someone explain to me the rationale behind the ANSI
>decision?  I understand that it has something to do with varargs, but
>I don't know what.  The ANSI restriction that there must be at least
>one fixed argument seems obviously artificial.

Some implementations would much prefer to pass "normal" non-variadic
arguments in a different, more efficient way than what they would have
to use for variadic arguments.  The fixed argument is for an "anchor"
to help va_start locate the first variadic argument; this could be
done with the help of compiler intrinsics, but it was felt that many
implementations would not need such kludges if an anchor were present.