linux-kernel - Re: [PATCH] scsi: lpfc: avoid false-positive gcc-8 warning

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Date:   Wed, 23 Aug 2017 09:20:52 -0700
From:   James Smart <james.smart@...adcom.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Dick Kennedy <dick.kennedy@...adcom.com>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Hannes Reinecke <hare@...e.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: lpfc: avoid false-positive gcc-8 warning

On 8/23/2017 8:01 AM, Arnd Bergmann wrote:
> This is an interesting regression with gcc-8, showing a harmless
> warning for correct code:
>
> In file included from include/linux/kernel.h:13:0,
>                   ...
>                   from drivers/scsi/lpfc/lpfc_debugfs.c:23:
> include/linux/printk.h:301:2: error: 'eq' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>    printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
>    ^~~~~~
> In file included from drivers/scsi/lpfc/lpfc_debugfs.c:58:0:
> drivers/scsi/lpfc/lpfc_debugfs.h:451:31: note: 'eq' was declared here
>
> I tried to come up with a reduced test case for gcc here
> a few times, but every time ended up with code that is actually
> wrong with older gcc versions missing the bug and gcc-8 finding
> it. As this is the only false-positive -Wmaybe-uninitialized
> warnign I got with gcc-8 randconfig builds, I'd suggest we
> work around it.
>
> Making the index variable 'unsigned' is enough to shut up
> the warning, as gcc can then see that comparing eqidx to
> phba->io_channel_irqs is fine here.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   drivers/scsi/lpfc/lpfc_debugfs.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
>
looks good. Thanks

Signed-off-by: James Smart <james.smart@...adcom.com>

-- james