Date: Mon, 13 Nov 2006 10:18:48 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: phk@phk.freebsd.dk Cc: jkoshy@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org, bde@zeta.org.au, cvs-src@freebsd.org Subject: Re: cvs commit: src/include ar.h Message-ID: <20061113.101848.-1558770561.imp@bsdimp.com> In-Reply-To: <3801.1163410519@critter.freebsd.dk> References: <20061113173927.Q75708@delplex.bde.org> <3801.1163410519@critter.freebsd.dk>
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In message: <3801.1163410519@critter.freebsd.dk>
"Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
: In message <20061113173927.Q75708@delplex.bde.org>, Bruce Evans writes:
: >On Mon, 13 Nov 2006, Joseph Koshy wrote:
: >
: >> jkoshy 2006-11-13 04:28:29 UTC
: >>
: >> FreeBSD src repository
: >>
: >> Modified files:
: >> include ar.h
: >> Log:
: >> Attempt to improve application portability by marking `struct ar_hdr'
: >> as `packed'.
: >>
: >> The C standard leaves the alignment of individual members of a C
: >> struct upto the implementation, so pedantically speaking portable
: >> code cannot assume that the layout of a `struct ar_hdr' in memory
: >> will match its layout in a file. Using a __packed attribute
: >> declaration forces file and memory layouts for this structure to
: >> match.
: >>
: >> Submitted by: ru
: >
: >I don't see how this can be more portable.
:
: I agree with bruce that __packed is not the way to go.
:
: For things that represent communication protocols, even if
: they happen through files, I advocate using the functions
: in sys/endian.h to explicitly decode and encode fields into
: bytestrings.
Until that happens, __packed is the only way to get correct code on
the arm.
Warner
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