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From: Joe Perches <joe@perches.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Kees Cook <keescook@chromium.org>,
	Martin Kletzander <mkletzan@redhat.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Maurizio Lombardi <mlombard@redhat.com>,
	Tejun Heo <tj@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 04/14] lib/vsprintf.c: expand field_width to 24 bits
Date: Thu, 03 Dec 2015 16:03:02 -0800	[thread overview]
Message-ID: <1449187382.17296.16.camel@perches.com> (raw)
In-Reply-To: <20151203153407.85761faeab07e7c2fed84e81@linux-foundation.org>

On Thu, 2015-12-03 at 15:34 -0800, Andrew Morton wrote:
> I've been fiddling with a BUILD_BUG_ON which works outside functions
> using gcc's __COUNTER__ - something like
> 
> #define BBO(expr) typedef char __bbo##__COUNTER__[1-2*(!!expr)]

nit:  you need another parenthesis around expr

> BBO(1 == 1);
> BBO(2 == 2);
> 
> but that comes out as
> 
> typedef char __bbo__COUNTER__[1-2*(!!1 == 1)];
> typedef char __bbo__COUNTER__[1-2*(!!2 == 2)];
> 
> instead of
> 
> typedef char __bbo0[1-2*(!!1 == 1)];
> typedef char __bbo1[1-2*(!!2 == 2)];
> 
> There's some trick here but I've forgotten what it is.

I believe it's something like:

#define __stringify_2(a, b)	a##b
#define __stringify2(a, b)	__stringify_2(a, b)

#define BBO(expr) typedef char __stringify2(bbo, __COUNTER__)[1 - 2*(!!(expr))]

  reply	other threads:[~2015-12-04  0:03 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-03 20:50 [PATCH v3 00/14] printf stuff for 4.5 Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 01/14] lib/vsprintf.c: pull out padding code from dentry_name() Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 02/14] lib/vsprintf.c: move string() below widen_string() Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 03/14] lib/vsprintf.c: eliminate potential race in string() Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 04/14] lib/vsprintf.c: expand field_width to 24 bits Rasmus Villemoes
2015-12-03 20:54   ` Joe Perches
2015-12-03 21:28     ` Andy Shevchenko
2015-12-03 23:34       ` Andrew Morton
2015-12-04  0:03         ` Joe Perches [this message]
2015-12-04  8:59           ` Rasmus Villemoes
2015-12-04  9:02         ` Rasmus Villemoes
2015-12-03 23:41       ` Joe Perches
2015-12-03 20:51 ` [PATCH v3 05/14] lib/vsprintf.c: help gcc make number() smaller Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 06/14] lib/vsprintf.c: warn about too large precisions and field widths Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 07/14] lib/kasprintf.c: add sanity check to kvasprintf Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 08/14] lib/test_printf.c: don't BUG Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 09/14] lib/test_printf.c: check for out-of-bound writes Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 10/14] lib/test_printf.c: test precision quirks Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 11/14] lib/test_printf.c: add a few number() tests Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 12/14] lib/test_printf.c: account for kvasprintf tests Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 13/14] lib/test_printf.c: add test for large bitmaps Rasmus Villemoes
2015-12-03 20:51 ` [PATCH v3 14/14] lib/test_printf.c: test dentry printing Rasmus Villemoes
2015-12-04  0:19   ` Andrew Morton
2015-12-04  8:16     ` Rasmus Villemoes
2015-12-04  8:46       ` Andrew Morton

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