Date: Mon, 13 Nov 2006 09:35:19 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Bruce Evans <bde@zeta.org.au> Cc: Joseph Koshy <jkoshy@FreeBSD.org>, src-committers@FreeBSD.org, cvs-all@FreeBSD.org, cvs-src@FreeBSD.org Subject: Re: cvs commit: src/include ar.h Message-ID: <3801.1163410519@critter.freebsd.dk> In-Reply-To: Your message of "Mon, 13 Nov 2006 19:30:11 %2B1100." <20061113173927.Q75708@delplex.bde.org>
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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. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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