From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Victoria Dye via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, derrickstolee@github.com,
Victoria Dye <vdye@github.com>
Subject: Re: [PATCH] read-cache: avoid misaligned reads in index v4
Date: Fri, 23 Sep 2022 15:04:10 -0700 [thread overview]
Message-ID: <xmqqtu4xsq79.fsf@gitster.g> (raw)
In-Reply-To: <Yy4nkEnhuzt2iH+R@coredump.intra.peff.net> (Jeff King's message of "Fri, 23 Sep 2022 17:39:28 -0400")
Jeff King <peff@peff.net> writes:
> Here (and elsewhere), you can assume that the offsetof() "sec" in
> cache_time is 0, for two reasons:
>
> - I didn't look up chapter and verse, but I'm pretty sure the standard
> does guarantee that the first field of a struct is at the beginning.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf
6.7.2.1 #13 (page 103)
Within a structure object, the non-bit-field members and the
units in which bit-fields reside have addresses that increase in
the order in which they are declared. A pointer to a structure
object, suitably converted, points to its initial member (or if
that member is a bit-field, then to the unit in which it
resides), and vice versa. There may be unnamed padding within a
structure object, but not at its beginning.
As an initial padding is forbidden, the first member's offset is zero.
next prev parent reply other threads:[~2022-09-23 22:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 19:43 [PATCH] read-cache: avoid misaligned reads in index v4 Victoria Dye via GitGitGadget
2022-09-23 21:39 ` Jeff King
2022-09-23 22:04 ` Junio C Hamano [this message]
2022-09-26 15:39 ` Victoria Dye
2022-09-26 17:35 ` Jeff King
2022-09-26 19:08 ` Jeff King
2022-09-26 19:31 ` Jeff King
2022-09-26 23:02 ` Junio C Hamano
2022-09-25 8:25 ` Phillip Wood
2022-09-26 17:54 ` Junio C Hamano
2022-09-28 17:19 ` [PATCH v2] " Victoria Dye via GitGitGadget
2022-09-28 17:34 ` Junio C Hamano
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