From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 8/9] net: nb8800: avoid uninitialized variable warning Date: Wed, 27 Jan 2016 16:21:54 +0100 Message-ID: <8558854.EA4z9rFkjX@wuerfel> References: <1453903507-3427225-1-git-send-email-arnd@arndb.de> <1453903507-3427225-9-git-send-email-arnd@arndb.de> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "David S. Miller" , linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= Return-path: Received: from mout.kundenserver.de ([212.227.17.10]:65204 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932740AbcA0PWa convert rfc822-to-8bit (ORCPT ); Wed, 27 Jan 2016 10:22:30 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wednesday 27 January 2016 14:13:16 M=E5ns Rullg=E5rd wrote: > Arnd Bergmann writes: >=20 > > 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] >=20 > 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 unde= r a > condition that can only be true if the first one was. Of course fixi= ng > 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 configuratio= n. The only time I see it in my logs was with CONFIG_ARCH_IXP4XX=3Dy, whic= h 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 >=20 > Acked-by: Mans Rullgard Thanks, Arnd