From: Paul Eggert <eggert@cs.ucla.edu>
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] dlfcn: Avoid one-element flexible array in Dl_serinfo
Date: Fri, 24 May 2019 16:47:44 -0700 [thread overview]
Message-ID: <d8732d23-4ebc-1530-bc37-1945778d05fe@cs.ucla.edu> (raw)
In-Reply-To: <8736l4utui.fsf@oldenburg2.str.redhat.com>
On 5/24/19 1:42 AM, Florian Weimer wrote:
> This changes the size of the type and is not source-code-compatible. I
> have not investigated whether the change is still reasonably safe, but
> usually, wo do not make such changes.
OK, in that case I suggest adding a comment explaining the situation,
since it is a bit of a sore thumb. Something like the following perhaps?
Or if this problem is likely to occur elsewhere, we could package the
situation up into a macro and just use the macro here.
/* An array of dls_cnt elements, each of type Dl_serpath. */
#if 0
/* With no backward-compatibility concerns we’d use the following
C99 flexible array member. However, as this data structure
predates C99 it had to contain a one-element array here, and we
don't want to change the struct's size now. */
Dl_serpath dls_serpath[];
#elif defined __GNUC__
/* Avoid an unwanted array subscript check by the compiler, while
preserving the size of the type. */
__extension__ union
{
Dl_serpath dls_serpath[0]; /* Actually longer, dls_cnt elements. */
Dl_serpath __dls_serpath_pad[1];
};
#else
Dl_serpath dls_serpath[1];
#endif
next prev parent reply other threads:[~2019-05-24 23:47 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-23 9:34 [PATCH] dlfcn: Avoid one-element flexible array in Dl_serinfo Florian Weimer
2019-05-23 22:42 ` Paul Eggert
2019-05-23 22:50 ` Joseph Myers
2019-05-24 8:42 ` Florian Weimer
2019-05-24 23:47 ` Paul Eggert [this message]
2019-05-27 19:04 ` Florian Weimer
2019-06-01 8:48 ` Paul Eggert
2019-06-03 7:59 ` Florian Weimer
-- strict thread matches above, loose matches on Subject: below --
2019-06-03 15:37 Florian Weimer
2019-06-18 14:27 ` Florian Weimer
2019-06-18 22:17 ` Paul Eggert
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