From owner-cvs-all  Tue May 14 11:41:37 2002
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To: Brian Somers <brian@FreeBSD.org>
Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/usr.sbin/ppp cbcp.c
References: <200205141332.g4EDWUG59102@freefall.freebsd.org>
From: Dag-Erling Smorgrav <des@ofug.org>
Date: 14 May 2002 20:41:26 +0200
In-Reply-To: <200205141332.g4EDWUG59102@freefall.freebsd.org>
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Brian Somers <brian@FreeBSD.org> writes:

> brian       2002/05/14 06:32:30 PDT
>=20
>   Modified files:
>     usr.sbin/ppp         cbcp.c=20
>   Log:
>   Avoid a rather bizarre warning from gcc 3.1:
>=20=20=20
>   /usr/src/usr.sbin/ppp/cbcp.c:566:61: warning: trigraph ??! ignored

It's not bizarre at all - trigraphs are possibly the most reviled
feature of C89, meant to provide alternatives to some characters such
as [ ] { } ~ | which in some character sets common on PCs at that time
were replaced with national characters (for instance, [ ] looked like
=C6 =C5 on computers using "Norwegian ASCII", before we got codepage 865).
'??!'  is the trigraph sequnce for '|'.  Here's the full set:

       5.2.1.1  Trigraph sequences

       [#1]  All  occurrences  in  a  source  file of the following
       sequences of three characters (called trigraph sequences11))
       are replaced with the corresponding single character.

            ??=3D     #         ??)     ]         ??!     |
            ??(     [         ??'     ^         ??>     }
            ??/     \         ??<     {         ??-     ~

       No other trigraph sequences exist.  Each ?   that  does  not
       begin one of the trigraphs listed above is not changed.

       [#2] EXAMPLE  The following source line

               printf("Eh???/n");

       becomes (after replacement of the trigraph sequence ??/)

               printf("Eh?\n");

Trigraphs are so unpopular (and useless on modern systems) that GCC
just warns about them, without converting them to the corresponding
single character.

DES
--=20
Dag-Erling Smorgrav - des@ofug.org

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