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From: Florian Weimer <fweimer@redhat.com>
To: Simon Chopin <simon.chopin@canonical.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] libquadmath: printf: fix misaligned access on args
Date: Tue, 02 Apr 2024 14:38:38 +0200	[thread overview]
Message-ID: <87a5mcx7ld.fsf@oldenburg3.str.redhat.com> (raw)
In-Reply-To: <20240312190352.3455451-1-simon.chopin@canonical.com> (Simon Chopin's message of "Tue, 12 Mar 2024 20:03:52 +0100")

* Simon Chopin:

> On x86, this compiles into movdqa which segfaults on unaligned access.
>
> This kind of failure has been seen when running against glibc 2.39,
> which incidentally changed the printf implementation to move away from
> alloca() for this data to instead append it at the end of an existing
> "scratch buffer", with arbitrary alignement, whereas alloca() was
> probably more likely to be naturally aligned.

This glibc change appears to be incorrect.  I think we need to preserve
ABI alignment for types than can be passed through the vararg interface.
I'm not sure if this easily possible, though.  Certainly needs a
discussion on libc-alpha.

Thanks,
Florian


  reply	other threads:[~2024-04-02 12:38 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-12 19:03 Simon Chopin
2024-04-02 12:38 ` Florian Weimer [this message]
2024-04-03  8:16 ` [committed] libquadmath: Don't assume the storage for __float128 arguments is aligned [PR114533] Jakub Jelinek

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