From: Matt Coster <Matt.Coster@imgtec.com>
To: "linux-sparse@vger.kernel.org" <linux-sparse@vger.kernel.org>
Subject: [BUG] Alignment of structure members does not always propagate
Date: Thu, 3 Jul 2025 11:19:28 +0000 [thread overview]
Message-ID: <ea14a74d-2da3-480e-bb84-33904aaeb10b@imgtec.com> (raw)
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Hi,
I started investigating this in response to [1], where it appears an
aligned attribute on a structure member is not being propagated out to
the containing structure by Sparse.
Removing the explicit alignment on the containing structure appears to
resolve this issue, suggesting to me that Sparse *can* correctly
evaluate the overall structure alignment, but that this value is
overridden by the explicit alignment attribute rather than (correctly)
being coerced upwards.
Here's a minimal reproduction, which compiles just fine with gcc/clang
but fails both assertions with Sparse (which considers the "correct"
size and alignment to be 8).
struct outer_struct {
int member __attribute__((__aligned__(64)));
} __attribute__((__aligned__(8)));
_Static_assert(sizeof(struct outer_struct) == 64, "bad size");
_Static_assert(_Alignof(struct outer_struct) == 64, "bad align");
I don't really have time myself to dig into this any further, but I
wanted to share what I'd discovered so far in case somebody far more
knowledgeable than myself can easily identify the issue within Sparse.
Cheers,
Matt
[1]: https://lore.kernel.org/r/20250606-sprase-reasoning-comments-v1-1-433c0ff11a09@imgtec.com
--
Matt Coster
E: matt.coster@imgtec.com
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reply other threads:[~2025-07-03 11:19 UTC|newest]
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