From: Arnd Bergmann <arnd@arndb.de>
To: "Måns Rullgård" <mans@mansr.com>
Cc: "David S. Miller" <davem@davemloft.net>,
linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/9] net: nb8800: avoid uninitialized variable warning
Date: Wed, 27 Jan 2016 16:21:54 +0100 [thread overview]
Message-ID: <8558854.EA4z9rFkjX@wuerfel> (raw)
In-Reply-To: <yw1xsi1jjekj.fsf@unicorn.mansr.com>
On Wednesday 27 January 2016 14:13:16 Måns Rullgård wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
>
> > The nb8800_poll() function initializes the 'next' variable in the
> > loop looking for new input data. We know this will be called at
> > least once because 'budget' is a guaranteed to be a positive number
> > when we enter the function, but the compiler doesn't know that
> > and warns when the variable is used later:
> >
> > drivers/net/ethernet/aurora/nb8800.c: In function 'nb8800_poll':
> > drivers/net/ethernet/aurora/nb8800.c:350:21: warning: 'next' may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> Which gcc version is this? 4.9 doesn't warn here, presumably because
> it's clever enough to notice that the offending use of 'next' is under a
> condition that can only be true if the first one was. Of course fixing
> the code so older compilers don't warn is a good idea.
This was with gcc-5.2.1, but possibly in an unusual kernel configuration.
The only time I see it in my logs was with CONFIG_ARCH_IXP4XX=y, which
has its own mach/io.h and other headers that sometimes override generic
functions with a more elaborate version.
I have another patch for ixp4xx that simplifies its mach/io.h in order to
get rid of other false 'uninitialized use' warnings, but this one still
shows up with that other patch.
> > Changing the 'while() {}' loop to 'do {} while()' makes it obvious
> > to the compiler what is going on so it no longer warns.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Acked-by: Mans Rullgard <mans@mansr.com>
Thanks,
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 8/9] net: nb8800: avoid uninitialized variable warning
Date: Wed, 27 Jan 2016 16:21:54 +0100 [thread overview]
Message-ID: <8558854.EA4z9rFkjX@wuerfel> (raw)
In-Reply-To: <yw1xsi1jjekj.fsf@unicorn.mansr.com>
On Wednesday 27 January 2016 14:13:16 M?ns Rullg?rd wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
>
> > The nb8800_poll() function initializes the 'next' variable in the
> > loop looking for new input data. We know this will be called at
> > least once because 'budget' is a guaranteed to be a positive number
> > when we enter the function, but the compiler doesn't know that
> > and warns when the variable is used later:
> >
> > drivers/net/ethernet/aurora/nb8800.c: In function 'nb8800_poll':
> > drivers/net/ethernet/aurora/nb8800.c:350:21: warning: 'next' may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> Which gcc version is this? 4.9 doesn't warn here, presumably because
> it's clever enough to notice that the offending use of 'next' is under a
> condition that can only be true if the first one was. Of course fixing
> the code so older compilers don't warn is a good idea.
This was with gcc-5.2.1, but possibly in an unusual kernel configuration.
The only time I see it in my logs was with CONFIG_ARCH_IXP4XX=y, which
has its own mach/io.h and other headers that sometimes override generic
functions with a more elaborate version.
I have another patch for ixp4xx that simplifies its mach/io.h in order to
get rid of other false 'uninitialized use' warnings, but this one still
shows up with that other patch.
> > Changing the 'while() {}' loop to 'do {} while()' makes it obvious
> > to the compiler what is going on so it no longer warns.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> Acked-by: Mans Rullgard <mans@mansr.com>
Thanks,
Arnd
next prev parent reply other threads:[~2016-01-27 15:22 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-27 14:04 [PATCH 0/9] network driver fixes Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 1/9] net: davinci_cpdma: use dma_addr_t for DMA address Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 2/9] net: hp100: remove unnecessary #ifdefs Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 3/9] net: bgmac: clarify CONFIG_BCMA dependency Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 16:11 ` Paul Gortmaker
2016-01-27 16:11 ` Paul Gortmaker
2016-01-27 16:11 ` Paul Gortmaker
2016-01-28 8:49 ` Arnd Bergmann
2016-01-28 8:49 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 4/9] net: moxart: use correct accessors for DMA memory Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-28 12:36 ` David Laight
2016-01-28 12:36 ` David Laight
2016-01-28 16:53 ` Arnd Bergmann
2016-01-28 16:53 ` Arnd Bergmann
2016-01-28 16:58 ` Arnd Bergmann
2016-01-28 16:58 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 5/9] net: fddi/defxx: avoid warning about uninitialized variable use Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 15:15 ` Maciej W. Rozycki
2016-01-27 15:15 ` Maciej W. Rozycki
2016-01-27 14:04 ` [PATCH 6/9] net: vxge: avoid unused function warnings Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 7/9] net: macb: avoid uninitialized variables Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 15:51 ` Nicolas Ferre
2016-01-27 15:51 ` Nicolas Ferre
2016-01-27 16:04 ` Nicolas Ferre
2016-01-27 16:04 ` Nicolas Ferre
2016-01-28 16:32 ` Arnd Bergmann
2016-01-28 16:32 ` Arnd Bergmann
2016-01-28 13:27 ` Sergei Shtylyov
2016-01-28 13:27 ` Sergei Shtylyov
2016-01-27 14:04 ` [PATCH 8/9] net: nb8800: avoid uninitialized variable warning Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-27 14:13 ` Måns Rullgård
2016-01-27 14:13 ` Måns Rullgård
2016-01-27 15:21 ` Arnd Bergmann [this message]
2016-01-27 15:21 ` Arnd Bergmann
2016-01-27 14:04 ` [PATCH 9/9] net: tg3: " Arnd Bergmann
2016-01-27 14:04 ` Arnd Bergmann
2016-01-29 0:14 ` [PATCH 0/9] network driver fixes David Miller
2016-01-29 0:14 ` David Miller
2016-01-29 12:56 ` Arnd Bergmann
2016-01-29 12:56 ` Arnd Bergmann
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