From: "Joseph S. Myers" <jsm28@cam.ac.uk>
To: Mark Mitchell <mark@codesourcery.com>
Cc: <gcc@gcc.gnu.org>
Subject: Re: C ABI: struct/union inconsistency
Date: Fri, 27 Sep 2002 09:33:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.33.0209271715380.29516-100000@kern.srcf.societies.cam.ac.uk> (raw)
In-Reply-To: <200209252358.g8PNwBG01380@localhost.localdomain>
On Wed, 25 Sep 2002, Mark Mitchell wrote:
> Accepting empty structures in C is an extension, but structures like S
> (i.e., with a single zero-width bitfield) are part of the language.
They are not; a structure with no named members is undefined behavior
(6.7.2.1#7), and a zero-width bit-field may not be named (6.7.2.1#3).
> might be. I also do not know if some piece of code in the Linux
> kernel is going to depend on the current behavior; we might want to
> have a switch for the old behavior.
Linux uses size 0 empty structures for efficiency (types that only need be
nonempty in SMP kernels), but only with sufficiently recent GCC; with
older GCC nonempty dummy structures are used because of compiler bugs.
--
Joseph S. Myers
jsm28@cam.ac.uk
next prev parent reply other threads:[~2002-09-27 16:21 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-27 8:59 Mark Mitchell
2002-09-27 9:33 ` Joseph S. Myers [this message]
2002-09-27 10:09 ` Richard Henderson
2002-09-27 10:31 ` Mark Mitchell
2002-09-27 11:41 ` Richard Henderson
2002-09-27 11:54 ` Gabriel Dos Reis
2002-09-27 13:44 ` Mark Mitchell
2002-09-27 15:11 ` Richard Henderson
2002-09-27 15:18 ` Mark Mitchell
2002-09-27 16:26 ` Richard Henderson
2002-09-27 17:53 ` Mark Mitchell
2002-09-27 18:51 ` David S. Miller
2002-09-27 19:01 ` Mark Mitchell
2002-09-27 19:54 ` Richard Henderson
2002-09-28 10:38 ` Tim Hollebeek
2002-09-28 12:56 ` Mark Mitchell
2002-09-28 13:00 ` Richard Henderson
2002-09-28 13:52 ` Mark Mitchell
2002-09-30 9:20 ` Gabriel Paubert
2002-09-30 10:22 ` Gabriel Dos Reis
2002-09-28 16:55 ` Per Bothner
2002-09-29 2:40 ` Tim Hollebeek
2002-09-27 20:02 ` Michael S. Zick
2002-09-28 9:01 ` Fergus Henderson
2002-09-27 20:43 ` Hans-Peter Nilsson
2002-09-28 16:55 ` Alexandre Oliva
2002-09-28 7:02 Robert Dewar
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