From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2512 invoked by alias); 9 Apr 2003 22:46:01 -0000 Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-prs-owner@gcc.gnu.org Received: (qmail 2495 invoked by uid 71); 9 Apr 2003 22:46:01 -0000 Date: Wed, 09 Apr 2003 22:46:00 -0000 Message-ID: <20030409224601.2494.qmail@sources.redhat.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, From: Richard Henderson Subject: Re: c/10360: __alignof__(double) answer 8 Reply-To: Richard Henderson X-SW-Source: 2003-04/txt/msg00403.txt.bz2 List-Id: The following reply was made to PR c/10360; it has been noted by GNATS. From: Richard Henderson To: Frederic De Jaeger Cc: rth@gcc.gnu.org, discuss-gnustep@gnu.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org, richard@brainstorm.co.uk, thoran@free.fr, gcc-gnats@gcc.gnu.org Subject: Re: c/10360: __alignof__(double) answer 8 Date: Wed, 9 Apr 2003 15:40:39 -0700 On Wed, Apr 09, 2003 at 11:59:58PM +0200, Frederic De Jaeger wrote: > Thus, why gcc does not align fields with respect to this *preferred* > alignment? Because the ABI says not to. > How can I compute the address of a field in a record? offsetof. > I need to do this uniformly on all the types. That means I cannot use > the trick : > offset = (char *)&foo.bla - (char *)&foo. > or the "offsetof" macro. Tough luck then. > ... and we expect it to return the alignment used by the compiler (and not > the *preferred* alignment). A meaningless number. Because "the alignment used by the compiler" is going to depend on the context in which it is used. r~