From: Arnd Bergmann <arnd@arndb.de>
To: James Bottomley <jejb@linux.ibm.com>
Cc: John Garry <john.garry@huawei.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Bottomley <James.Bottomley@steeleye.com>,
Hannes Reinecke <hare@suse.com>,
linux-scsi <linux-scsi@vger.kernel.org>
Subject: Re: [PATCH 13/15] scsi: sas: avoid gcc-10 zero-length-bounds warning
Date: Fri, 1 May 2020 19:36:55 +0200 [thread overview]
Message-ID: <CAK8P3a2nTi6AOf-4xJN3wurCXC52mLPBVbjgvcv6Cz=8A05X0A@mail.gmail.com> (raw)
In-Reply-To: <1588344818.3428.18.camel@linux.ibm.com>
On Fri, May 1, 2020 at 4:53 PM James Bottomley <jejb@linux.ibm.com> wrote:
> On Fri, 2020-05-01 at 09:54 +0200, Arnd Bergmann wrote:
> > On Fri, May 1, 2020 at 9:48 AM John Garry <john.garry@huawei.com>
> > wrote:
> > I found one hack that would work, but I think it's too ugly and
> > likely not well-defined either:
> >
> > struct ssp_response_iu {
> > ...
> > struct {
> > u8 dummy[0]; /* a struct must have at least one
> > non-flexible member */
>
> If gcc is now warning about zero length members, why isn't it warning
> about this one ... are unions temporarily excluded?
It does not warn about all zero-length arrays, but it does warn when you
try to access an array with an out-of-range index, and this apparently
got extended in gcc-10 to any index for zero-length arrays.
> > u8 resp_data[]; /* allowed here because it's at
> > the one of a struct */
> > };
> > u8 sense_data[];
> > } __attribute__ ((packed));
>
> Let's go back to what the standard says: we want the data beyond the
> ssp_response_iu to be addressable either as sense_data if it's an error
> return or resp_data if it's a real response. What about trying to use
> an alias attribute inside the structure ... will that work on gcc-10?
I think alias attributes only work for functions and variables, but not
for struct members.
A "#define sense_data resp_data" would obviously work, but it's
rather error-prone when other code uses the same identifiers.
Another option would be an inline helper like
static inline u8 *ssp_response_data(struct ssp_response_iu *iu)
{
return iu.resp_data;
}
Arnd
next prev parent reply other threads:[~2020-05-01 17:37 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 21:30 [PATCH 00/15] gcc-10 warning fixes Arnd Bergmann
2020-04-30 21:30 ` [PATCH 01/15] crypto - Avoid free() namespace collision Arnd Bergmann
2020-05-08 6:06 ` Herbert Xu
2020-04-30 21:30 ` [PATCH 02/15] iwlwifi: mvm: fix gcc-10 zero-length-bounds warning Arnd Bergmann
2020-06-10 12:18 ` Luciano Coelho
2020-04-30 21:30 ` [PATCH 03/15] mwifiex: avoid -Wstringop-overflow warning Arnd Bergmann
2020-05-06 8:43 ` Kalle Valo
2020-04-30 21:30 ` [PATCH 04/15] ath10k: fix gcc-10 zero-length-bounds warnings Arnd Bergmann
2020-04-30 21:45 ` Gustavo A. R. Silva
2020-04-30 21:44 ` Arnd Bergmann
2020-05-04 11:54 ` Kalle Valo
2020-05-04 16:09 ` Gustavo A. R. Silva
2020-05-05 4:56 ` Kalle Valo
2020-04-30 21:30 ` [PATCH 05/15] bpf: avoid gcc-10 stringop-overflow warning Arnd Bergmann
2020-05-04 21:06 ` Daniel Borkmann
2020-04-30 21:30 ` [PATCH 06/15] netfilter: conntrack: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-05-10 21:48 ` Pablo Neira Ayuso
2020-04-30 21:30 ` [PATCH 07/15] drop_monitor: work around gcc-10 stringop-overflow warning Arnd Bergmann
2020-05-01 11:28 ` Neil Horman
2020-04-30 21:30 ` [PATCH 08/15] usb: ehci: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-05-01 2:42 ` Alan Stern
2020-05-01 20:06 ` Arnd Bergmann
2020-05-01 20:10 ` Alan Stern
2020-04-30 21:30 ` [PATCH 09/15] udf: avoid gcc-10 zero-length-bounds warnings Arnd Bergmann
2020-04-30 21:54 ` Pali Rohár
2020-05-01 20:30 ` Arnd Bergmann
2020-05-01 20:48 ` Jan Kara
2020-05-01 20:57 ` Pali Rohár
2020-04-30 21:30 ` [PATCH 10/15] hpfs: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-04-30 21:30 ` [PATCH 11/15] omfs: avoid gcc-10 stringop-overflow warning Arnd Bergmann
2020-04-30 21:30 ` [PATCH 12/15] media: s5k5baf: avoid gcc-10 zero-length-bounds warning Arnd Bergmann
2020-04-30 21:46 ` Gustavo A. R. Silva
2020-04-30 21:30 ` [PATCH 13/15] scsi: sas: " Arnd Bergmann
2020-05-01 7:47 ` John Garry
2020-05-01 7:54 ` Arnd Bergmann
2020-05-01 14:53 ` James Bottomley
2020-05-01 17:36 ` Arnd Bergmann [this message]
2020-04-30 21:30 ` [PATCH 14/15] isci: " Arnd Bergmann
2020-04-30 21:30 ` [PATCH 15/15] nvme: " Arnd Bergmann
2020-05-01 7:32 ` Christoph Hellwig
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