From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: [PATCH] Proposed removal of IS_ERR_OR_NULL() (was: Re: [PATCH 1/4] gpiolib: introduce descriptor-based GPIO interface) Date: Wed, 9 Jan 2013 15:04:28 +0000 Message-ID: <20130109150427.GL3931@n2100.arm.linux.org.uk> References: <1357629535-26033-1-git-send-email-acourbot@nvidia.com> <201301081259.29839.arnd@arndb.de> <201301091035.23206.arnd@arndb.de> <20130109104414.GF3931@n2100.arm.linux.org.uk> <20130109111055.GG3931@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:42814 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932073Ab3AIPEq (ORCPT ); Wed, 9 Jan 2013 10:04:46 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Nicolas Pitre Cc: Arnd Bergmann , linux-arch@vger.kernel.org, Linus Walleij , Linux Kernel Mailing List , Grant Likely , Alexandre Courbot , Guenter Roeck , "devicetree-discuss@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" So, it seems there's some concensus building here, and it seems that I've become the chosen victi^wvolunteer for this. So, here's a patch. It's missing a Guns-supplied-by: tag though. From: Russell King Subject: Mark IS_ERR_OR_NULL() deprecated IS_ERR_OR_NULL() attracts a lot of abuse: people use it without much thought about it's effects. Common errors include: 1. checking the returned pointer for functions defined as only returning errno-pointer values, rather than using IS_ERR(). This leads to: ptr = foo(); if (IS_ERR_OR_NULL(ptr)) return PTR_ERR(ptr); 2. using it to check functions which only ever return NULL on error, thereby leading to another zero-error value return. In the case of debugfs functions, these return errno-pointer values when debugfs is configured out, which means code which blindly checks using IS_ERR_OR_NULL() ends up returning errors, which is rather perverse for something that's not implemented. Therefore, let's schedule it for removal in a few releases. Nicolas Pitre comments: > I do agree with Russell here. Despite the original intentions behind > IS_ERR_OR_NULL() which were certainly legitimate, the end result in > practice is less reliable code with increased maintenance costs. > Unlike other convenience macros in the kernel, this one is giving a > false sense of correctness with too many people falling in the trap > of using it just because it is available. > > I strongly think this macro should simply be removed from the source > tree entirely and the code reverted to explicit tests against NULL > when appropriate. Suggested-by: David Howells Tape-measuring-service-offered-by: Will Deacon Victim-for-firing-sqad: Russell King Signed-off-by: Russell King --- Ok, so I'm in the firing line for suggesting this, but it appears several people wish this to happen. I'm not intending to push this patch forwards _just_ yet: we need to sort out the existing users _first_ to prevent the kernel turning into one hell of a mess of warnings. include/linux/err.h | 17 ++++++++++++++++- 1 files changed, 16 insertions(+), 1 deletions(-) diff --git a/include/linux/err.h b/include/linux/err.h index f2edce2..d5a85df 100644 --- a/include/linux/err.h +++ b/include/linux/err.h @@ -34,7 +34,22 @@ static inline long __must_check IS_ERR(const void *ptr) return IS_ERR_VALUE((unsigned long)ptr); } -static inline long __must_check IS_ERR_OR_NULL(const void *ptr) +/* + * IS_ERR_OR_NULL() attracts a lot of abuse: people use it without much + * thought about it's effects. Common errors include: + * 1. checking the returned pointer for functions defined as only returning + * errno-pointer values, rather than using IS_ERR(). + * This leads to: ptr = foo(); if (IS_ERR_OR_NULL(ptr)) return PTR_ERR(ptr); + * 2. using it to check functions which only ever return NULL on error, + * thereby leading to another zero-error value return. + * In the case of debugfs functions, these return errno-pointer values when + * debugfs is configured out, which means code which blindly checks using + * IS_ERR_OR_NULL() ends up returning errors, which is rather perverse for + * something that's not implemented. + * + * Therefore, let's schedule it for removal in a few releases. + */ +static inline long __must_check __deprecated IS_ERR_OR_NULL(const void *ptr) { return !ptr || IS_ERR_VALUE((unsigned long)ptr); }