From: Joseph Myers <joseph@codesourcery.com>
To: Kees Cook <keescook@chromium.org>
Cc: Alejandro Colomar <alx.manpages@gmail.com>, GCC <gcc@gcc.gnu.org>,
Alejandro Colomar <alx@nginx.com>,
Andrew Clayton <a.clayton@nginx.com>,
Andrew Clayton <andrew@digital-domain.net>,
<linux-hardening@vger.kernel.org>
Subject: Re: [wish] Flexible array members in unions
Date: Thu, 11 May 2023 20:53:52 +0000 [thread overview]
Message-ID: <74ee73d2-04e-ea8-9430-93929446e925@codesourcery.com> (raw)
In-Reply-To: <202305111158.C78642624@keescook>
On Thu, 11 May 2023, Kees Cook via Gcc wrote:
> On Thu, May 11, 2023 at 06:29:10PM +0200, Alejandro Colomar wrote:
> > On 5/11/23 18:07, Alejandro Colomar wrote:
> > [...]
> > > Would you allow flexible array members in unions? Is there any
> > > strong reason to disallow them?
>
> Yes please!! And alone in a struct, too.
>
> AFAICT, there is no mechanical/architectural reason to disallow them
> (especially since they _can_ be constructed with some fancy tricks,
> and they behave as expected.) My understanding is that it's disallowed
> due to an overly strict reading of the very terse language that created
> flexible arrays in C99.
Standard C has no such thing as a zero-size object or type, which would
lead to problems with a struct or union that only contains a flexible
array member there.
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2023-05-11 20:55 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <ac2550e0-2f5c-3680-08e6-0c224d043036@gmail.com>
[not found] ` <44940599-7b43-99f6-5b09-4f050d645c7b@gmail.com>
2023-05-11 19:07 ` [wish] Flexible array members in unions Kees Cook
2023-05-11 20:53 ` Joseph Myers [this message]
2023-05-11 21:13 ` Kees Cook
2023-05-11 21:43 ` Joseph Myers
2023-05-11 22:16 ` Kees Cook
2023-05-11 22:52 ` Joseph Myers
2023-05-12 0:25 ` Alejandro Colomar
2023-05-12 6:16 ` Richard Biener
2023-05-15 19:58 ` Qing Zhao
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