From: Jan Engelhardt <jengelh@inai.de>
To: David Howells <dhowells@redhat.com>
Cc: linux-api@vger.kernel.org, linux-kbuild@vger.kernel.org,
Coly Li <colyli@suse.de>,
Kent Overstreet <kent.overstreet@gmail.com>,
linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 04/11] UAPI: bcache: Fix use of embedded flexible array
Date: Tue, 2 Oct 2018 16:52:56 +0200 (CEST) [thread overview]
Message-ID: <nycvar.YFH.7.76.1810021622320.11696@n3.vanv.qr> (raw)
In-Reply-To: <153616290368.23468.7806230605345568524.stgit@warthog.procyon.org.uk>
On Wed, 05 Sep 2018 16:55:03 +0100, David Howells wrote:
>
>The bkey struct defined by bcache is embedded in the jset struct. However,
>this is illegal in C++ as there's a "flexible array" at the end of the struct.
>Change this to be a 0-length struct instead.
>
>- __u64 ptr[];
>+ __u64 ptr[0];
As per the C++ standard, it is _also_ illegal to declare an array of size zero.
"""it [the array size expression] shall be a converted constant expression of
type std::size_t and its value shall be greater than zero."""
—http://eel.is/c++draft/dcl.array
That makes both "__u64 ptr[]" and "__u64 ptr[0]" *implementation-specific
extensions*.
3rd party tooling (concerns both C and C++):
Coverity Scan (IIRC) treats "__u64 ptr[0]" as an array of "definitely-zero"
size. Writing to any element will outright flag an out-of-bounds violation.
That is sensible, since only "ptr[]" was standardized.
Conclusion:
So please, do never use __u64 ptr[0].
next prev parent reply other threads:[~2018-10-02 14:53 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-05 15:54 [RFC] UAPI: Check headers by compiling all together as C++ David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` [PATCH 01/11] UAPI: drm: Fix use of C++ keywords as structural members David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` [PATCH 02/11] UAPI: keys: " David Howells
2018-09-05 15:54 ` David Howells
2018-09-05 15:54 ` [PATCH 03/11] UAPI: virtio_net: " David Howells
2018-09-05 16:54 ` Greg KH
2018-09-05 16:54 ` Greg KH
2018-09-05 17:15 ` David Howells
2018-09-05 17:15 ` David Howells
2018-09-05 17:35 ` Michael S. Tsirkin
2018-09-05 17:35 ` Michael S. Tsirkin
2018-09-06 7:09 ` David Howells
2018-09-06 7:09 ` David Howells
2018-09-06 14:36 ` Michael S. Tsirkin
2018-09-06 14:36 ` Michael S. Tsirkin
2018-09-05 15:54 ` David Howells
2018-09-05 15:55 ` [PATCH 04/11] UAPI: bcache: Fix use of embedded flexible array David Howells
2018-10-02 14:52 ` Jan Engelhardt [this message]
2018-10-09 15:41 ` David Howells
2018-10-09 16:54 ` Jan Engelhardt
2018-09-05 15:55 ` [PATCH 05/11] UAPI: coda: Don't use internal kernel structs in UAPI David Howells
2018-09-05 16:54 ` Jan Harkes
2018-09-05 17:12 ` Yann Droneaud
2018-09-05 17:28 ` Jan Harkes
2018-09-05 17:28 ` Jan Harkes
2018-09-05 17:24 ` David Howells
2018-09-06 7:13 ` David Howells
2018-09-06 11:52 ` Yann Droneaud
2018-09-06 12:16 ` Jan Harkes
2018-09-06 12:16 ` Jan Harkes
2018-09-06 14:53 ` David Howells
2018-09-05 15:55 ` [PATCH 06/11] UAPI: netfilter: Fix symbol collision issues David Howells
2018-09-05 15:55 ` [PATCH 07/11] UAPI: nilfs2: Fix use of undefined byteswapping functions David Howells
2018-09-05 22:20 ` Al Viro
2018-09-05 15:55 ` [PATCH 08/11] UAPI: sound: Fix use of u32 and co. in UAPI headers David Howells
2018-09-05 15:55 ` David Howells
2018-09-06 5:59 ` Takashi Sakamoto
2018-09-06 5:59 ` Takashi Sakamoto
2018-09-06 8:17 ` David Howells
2018-09-05 15:55 ` [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers David Howells
2018-09-05 15:55 ` David Howells
2018-09-05 15:55 ` David Howells
2018-09-05 15:55 ` [PATCH 10/11] UAPI: ndctl: Remove use of PAGE_SIZE David Howells
2018-09-05 15:55 ` David Howells
2018-09-05 15:55 ` [PATCH 11/11] UAPI: Check headers build for C++ David Howells
2018-09-05 16:55 ` [RFC] UAPI: Check headers by compiling all together as C++ Greg KH
2018-09-05 16:55 ` Greg KH
2018-09-05 16:55 ` Greg KH
2018-09-05 16:55 ` Greg KH
2018-09-05 16:55 ` Greg KH
2018-09-05 17:33 ` Yann Droneaud
2018-09-05 17:33 ` Yann Droneaud
2018-09-05 17:33 ` Yann Droneaud
2018-09-05 17:33 ` Yann Droneaud
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-05 17:42 ` Michael S. Tsirkin
2018-09-06 7:12 ` Yann Droneaud
2018-09-06 7:12 ` Yann Droneaud
2018-09-06 7:12 ` Yann Droneaud
2018-09-06 7:12 ` Yann Droneaud
2018-09-05 19:22 ` Jan Engelhardt
2018-09-05 19:22 ` Jan Engelhardt
2018-09-05 19:22 ` Jan Engelhardt
2018-09-05 19:22 ` Jan Engelhardt
2018-09-05 19:22 ` Jan Engelhardt
2018-09-05 17:50 ` David Howells
2018-09-05 17:50 ` David Howells
2018-09-05 17:50 ` David Howells
2018-09-06 9:18 David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` David Howells
[not found] ` <153622549721.14298.8116794954073122489.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2018-09-06 9:18 ` [PATCH 01/11] UAPI: drm: Fix use of C++ keywords as structural members [ver #2] David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` [PATCH 02/11] UAPI: keys: " David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` [PATCH 03/11] UAPI: virtio_net: " David Howells
2018-09-06 15:02 ` Michael S. Tsirkin
2018-09-06 15:02 ` Michael S. Tsirkin
2018-09-06 9:18 ` David Howells
2018-09-06 9:18 ` [PATCH 04/11] UAPI: bcache: Fix use of embedded flexible array " David Howells
2018-09-06 9:18 ` [PATCH 05/11] UAPI: coda: Move kernel internals out of public view " David Howells
2018-09-06 9:18 ` David Howells
2018-09-06 9:19 ` [PATCH 06/11] coda: Move internal defs out of include/linux/ " David Howells
2018-09-06 9:19 ` [PATCH 07/11] UAPI: netfilter: Fix symbol collision issues " David Howells
2018-09-10 17:32 ` kbuild test robot
2018-09-10 17:32 ` kbuild test robot
2018-09-10 17:32 ` kbuild test robot
2018-09-28 13:07 ` [netfilter-core] " Pablo Neira Ayuso
2018-10-09 15:35 ` David Howells
2018-09-06 9:19 ` [PATCH 08/11] UAPI: nilfs2: Fix use of undefined byteswapping functions " David Howells
2018-09-06 9:19 ` [PATCH 09/11] UAPI: ndctl: Fix g++-unsupported initialisation in headers " David Howells
2018-09-06 9:19 ` David Howells
2018-09-06 9:19 ` David Howells
2018-09-25 20:22 ` Dan Williams
2018-09-25 20:22 ` Dan Williams
2018-09-25 20:22 ` Dan Williams
2018-09-06 9:19 ` [PATCH 10/11] UAPI: ndctl: Remove use of PAGE_SIZE " David Howells
2018-09-06 9:19 ` David Howells
2018-09-06 9:19 ` David Howells
2018-09-25 20:17 ` Dan Williams
2018-09-25 20:17 ` Dan Williams
2018-09-25 20:17 ` Dan Williams
2018-10-09 15:36 ` David Howells
2018-10-09 15:36 ` David Howells
2018-09-06 9:19 ` [PATCH 11/11] UAPI: Check headers build for C++ " David Howells
2018-09-10 16:26 ` kbuild test robot
2018-09-10 16:26 ` kbuild test robot
2018-09-10 16:26 ` kbuild test robot
2018-09-10 17:02 ` kbuild test robot
2018-09-10 17:02 ` kbuild test robot
2018-09-10 17:02 ` kbuild test robot
2018-09-14 9:10 ` Arnd Bergmann
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