linux-kernel - Re: [PATCH][RFC] Sparc: Remove trigraph in die_if

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Date:	Fri, 10 Jun 2011 09:51:22 +0200 (CEST)
From:	Jesper Juhl <jj@...osbits.net>
To:	David Miller <davem@...emloft.net>
cc:	viro@...IV.linux.org.uk, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] Sparc: Remove trigraph in die_if_kernel()
 message.

On Thu, 9 Jun 2011, David Miller wrote:

> From: Al Viro <viro@...IV.linux.org.uk>
> Date: Fri, 10 Jun 2011 00:03:22 +0100
> 
> > On Thu, Jun 09, 2011 at 03:59:43PM -0700, David Miller wrote:
> >> > If I'm not mistaken, that "??!" will be taken as a trigraph for "|" by the 
> >> > preprocessor, so the final string will end up either as
> >> >   "Penguin instruction from Penguin mode|?!"
> > 
> > Not without -trigraphs, which is not on by default...
> 
> Oh, in that case I'll rever this.
> 

Well, my gcc warns about it. It seems that -Wtrigraphs is enabled by 
default:

[jj@...gon src]$ gcc --version
gcc (GCC) 4.6.0 20110603 (prerelease)
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO                                                                                    
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR 
PURPOSE.

[jj@...gon src]$ cat test.c
#include <stdio.h>

int main()
{
  printf("Penguin instruction from Penguin mode??!?!");
  return 0;
}
[jj@...gon src]$ gcc test.c
test.c: In function ‘main’:
test.c:5:48: warning: trigraph ??! ignored, use -trigraphs to enable [-Wtrigraphs]

Which was why I wrote in my original submission mail :

"... which I assume is not what we want, or as the correct string but with 
a warning about an ignored trigraph which I assume we don't want either."

So either we get the wrong string (if someone enables -trigraphs) or we 
get a warning (at least with newer gcc's). Which is why I felt the patch 
made sense as a way to avoid both unfortunate results.

-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
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