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Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c

From: Florian Weimer <fweimer at redhat dot com>
To: John David Anglin <dave dot anglin at bell dot net>, Andreas Schwab <schwab at suse dot de>
Cc: GNU C Library <libc-alpha at sourceware dot org>, "Carlos O'Donell" <carlos at redhat dot com>, Mike Frysinger <vapier at gentoo dot org>
Date: Wed, 15 Jun 2016 16:43:39 +0200
Subject: Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
Authentication-results: sourceware.org; auth=none
References: <5E7CF115-219A-4260-BE53-19B5A8D1D7F3 at bell dot net> <d18a20fa-d486-7db4-e0bc-d6961a4499c2 at redhat dot com> <mvm60tazlxv dot fsf at hawking dot suse dot de> <5a20f0ea-0133-a380-0629-d377dc1c290c at bell dot net>

On 06/15/2016 04:40 PM, John David Anglin wrote:

On 2016-06-15 8:16 AM, Andreas Schwab wrote:

Florian Weimer<fweimer@redhat.com>  writes:

>On 06/15/2016 01:42 PM, John David Anglin wrote:

>>The attached patch fixes BZ 20243.  The HEADER struct needs to be
packed so that
>>byte accesses are used.  Tested using glibc 2.22-11on hppa.
Please install if okay.

>>-} HEADER;
>>+} __attribute__ ((packed)) HEADER;

I don't think the packed derivative affects the layout of HEADER given
the way the fields are
arranged.

I verified that it changes alignment, even on x86_64. That's theintent, and it results in a layout change (if this struct is used as apart of other structs, for example).


Florian

Follow-Ups:
- Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
  - From: John David Anglin

References:
- [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
  - From: John David Anglin
- Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
  - From: Florian Weimer
- Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
  - From: Andreas Schwab
- Re: [PATCH] Fix misaligned access accessing HEADER struct in res_query.c
  - From: John David Anglin

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