From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 2744B2C for ; Fri, 12 Aug 2016 05:38:54 +0000 (UTC) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 94C3311D for ; Fri, 12 Aug 2016 05:38:52 +0000 (UTC) Date: Fri, 12 Aug 2016 08:38:49 +0300 From: "Michael S. Tsirkin" To: Alexey Dobriyan Message-ID: <20160812083512-mutt-send-email-mst@kernel.org> References: <87inw1skws.fsf@x220.int.ebiederm.org> <25598.1469113525@warthog.procyon.org.uk> <18158a39-1297-7368-3c0e-3e9b3ce2c3ab@suse.com> <20160811154429.GB4134@mwanda> <20160812040155.kvw5322jqshtmljb@x> <20160812052919.GB2289@p183.telecom.by> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160812052919.GB2289@p183.telecom.by> Cc: Dan Carpenter , ksummit-discuss@lists.linuxfoundation.org Subject: Re: [Ksummit-discuss] [CORE TOPIC] More useful types in the linux kernel List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, Aug 12, 2016 at 08:29:20AM +0300, Alexey Dobriyan wrote: > On Fri, Aug 12, 2016 at 12:07:11AM -0400, Matthew Wilcox wrote: > > On Aug 11, 2016 9:02 PM, "Josh Triplett" wrote: > > > On Thu, Aug 11, 2016 at 11:51:52PM -0400, Matthew Wilcox wrote: > > > > Can we introduce types for this? We have a number of different return > > type > > > > conventions in the kernel: > > > > > > > > bool > > > > errno_t (-4095 to 0 are valid) > > > > count_t (-4095 to INT_MAX) > > > > long_count_t (-4095 to LONG_MAX) > > > > ulong_count_t (-4095 to -4096) > > > > struct foo _err* > > > > > > > > I think this is good programmer documentation in addition to being > > > > potentially useful to smatch. > > > > > > I'd love to see an explicit type distinct from "int" for "potentially an > > > errno". And if any code uses "potentially an errno *or* a non-errno > > > non-zero return value", that should ideally use a distinct type as well. > > > > I think the biggest problem is coming up with good names for the types. And > > the churn of introducing them, particularly converting function pointers > > and all occurrences. > > Names are easy part (errno_t is perfect actually). The problem is that > once error is cleared, variable doesn't change to regular type anymore: > > errno_t rv; > > rv = f(); > if (rv < 0) > return rv; > int rv = rv; > > which agains boils down to a language with real type system. We could maybe do errno_t rv; rv = f(); if (IS_ERR(rv)) return rv; int r = CHECKED(rv); Tools could maybe verify that all paths to CHECKED are actually going through an IS_ERR test as well. > _______________________________________________ > Ksummit-discuss mailing list > Ksummit-discuss@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/ksummit-discuss