From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751543AbcEYKHD (ORCPT ); Wed, 25 May 2016 06:07:03 -0400 Received: from mout.kundenserver.de ([217.72.192.73]:53573 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751109AbcEYKHA (ORCPT ); Wed, 25 May 2016 06:07:00 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Sudip Mukherjee , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, Herbert Xu , Maxime Coquelin , Matt Mackall Subject: Re: [PATCH] hwrng: stm32 - fix build warning Date: Wed, 25 May 2016 12:06:24 +0200 Message-ID: <7211115.EdoBLRGZ1i@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-22-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: <5745085D.6000104@gmail.com> References: <1464007448-25395-1-git-send-email-sudipm.mukherjee@gmail.com> <6297051.TAxtzW5OIB@wuerfel> <5745085D.6000104@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:HOd//QV5G/PPW5/j8vVwOMZ4iJrO3Y0i4wT1jdonAnHxT6Nbmcz n8Bplqh8A8AZi7BV30OORFMZsfCjkng5L+3qnc9eQj5PJFadx8T23raKkLCgjy40ogTLj1f DuDjdNJPFttjO3QHI9PgMLRbkExOvyIxq+g0k4R3zcW5146T0jWG+s6pTcL8M6aSF3gj9y8 eGMwV4FNWkyZ4cbx+OMlQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:R3e5UBAopYU=:MYG29ljTZJKjSy6XkynIjD 7xUfxHeMqbMp/568Gj4ilglH2OyGKjNq/HrKPOreNodqrKE8oZCvi7dPLEFLY/tLRJm7q8Wqf /Y99xreLsne3Wg0XsPba+Gtr9L83fJOBXpn//ToU9Pkym87B/Q5oEbtOpWCYrxrTlsPet8gRb tLwi0iM5yd3R/FbWPFnSvjO4+QOci3GB42Q+nFwqBhp6HbIi8sOoIM4/8pD/AZreNK4ZPm4/d vmA7rXWDfrV9c8CAudw4yfQVOVSTAhIpRJSzTWZJE6pwVkd7eOC5lGNNVM5X9eJEDY0niEx6y PCdN00+kNJzwTG7qwwYv029hbw3LZ4IZEpIZ1obCeVxERpGzEh2jLGmp3HFkwNOKsULJ35wOo jPBybE5T0az5VhNc2ZXJfaubjYGQCKX8ZaZU3B5PXnY42shZ4kBszgThqlxQ9BmKakkrzq+02 Ve1g2ishrqrNPa940vbQCEEZAHXnIzRAvrjjZL+DVk18hfrwjE7OPl2tM6WHT15E7UiK0nfeF ZJ1Y5UBTwxixa8uJVeG3V4KMX3fgH4yfGP3d9WdEeUelifO+FwFBJ4JYpf65n3eiRKWoI2rxR 4ZiiNzvdTTlEucEi+WzG7Jie2Rk+tJr5rh8H6Sh67NVi61Xx3vLNhJRPZqjlmBhTWSg98Kqbg laTA0sWEenNpFNu0lT0wtoiZAfu9pU6IWw9t3/ecMrWPESoGJU8JlwnaU53HCUK1LwkG3CKk1 2wa0sMDH1/xrM14T Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, May 25, 2016 7:35:17 AM CEST Sudip Mukherjee wrote: > On Tuesday 24 May 2016 02:05 AM, Arnd Bergmann wrote: > > On Monday, May 23, 2016 6:14:08 PM CEST Sudip Mukherjee wrote: > >> We have been getting build warning about: > >> drivers/char/hw_random/stm32-rng.c: In function 'stm32_rng_read': > >> drivers/char/hw_random/stm32-rng.c:82:19: warning: 'sr' may be used > >> uninitialized in this function > >> > >> On checking the code it turns out that sr can never be used > >> uninitialized as sr is getting initialized in the while loop and while > >> loop will always execute as the minimum value of max can be 32. > >> So just initialize sr to 0 while declaring it to silence the compiler. > >> > >> Signed-off-by: Sudip Mukherjee > >> --- > > > > I notice that you are using a really old compiler. While this warning > > seems to be valid in the sense that the compiler should figure out that > > the variable might be used uninitialized, please update your toolchain > > before reporting other such problems, as gcc-4.6 had a lot more false > > positives that newer ones (5.x or 6.x) have. > > yes, i need to upgrade gcc in my travis bot. But in my local system I am > having gcc-4.8.4 and there also I am having this error and i am sure > 4.8.4 is still being used by many people. Right, the change from gcc-4.8 to 4.9 is what drastically changed hte maybe-uninitialized warnings, introducing a number of additional warnings (many of them correct) but removing many others (mostly false positives). I tend to care only about the ones in 4.9+ for this reason. I haven't run statistics on this in a while, but I guess we could consider turning off this warning for 4.8 and earlier (though IIRC the switch to turn it off only appeared in 4.9). BTW, regarding your build infrastructure, I'd also recommend building with 'make -s' to make the output more compact. Arnd