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 697D971 for ; Tue, 26 Jul 2016 11:48:44 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 062F31EF for ; Tue, 26 Jul 2016 11:48:43 +0000 (UTC) Message-ID: <1469533716.120686.281.camel@infradead.org> From: David Woodhouse To: Hannes Reinecke , Julia Lawall Date: Tue, 26 Jul 2016 12:48:36 +0100 In-Reply-To: References: <87inw1skws.fsf@x220.int.ebiederm.org> <25598.1469113525@warthog.procyon.org.uk> <18158a39-1297-7368-3c0e-3e9b3ce2c3ab@suse.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-iXXjXMGijvcU5WIG3Rrn" Mime-Version: 1.0 Cc: 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: , --=-iXXjXMGijvcU5WIG3Rrn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2016-07-22 at 15:57 +0200, Hannes Reinecke wrote: >=20 > > I guess that almost all functions return only a few possible error code= s? >=20 > Precisely. If we had a way of specifying "the return value is an errno > with the possible values '0', '-EIO', and '-EINVAL'" that would be > _so_ cool. And perpetually out of date. Because functions call through to *other* functions which might return an errno outside the 'known' set. Any why would you *want* to know the precise set of errnos that a function might return, if not to deliberately code your error handling non-defensively? I can understand wanting to distinguish between errors and non-errors and ensure that the ranges cannot overlap. But IS_ERR_VALUE() typically reserves the whole range to -4095 (-MAX_ERRNO) for that. And I don't think we'd ever want to do anything different. In particular I don't want anyone ever saying "oh, -123 is a valid non- error return but no other negative numbers are. But that's OK because it'll never *actually* return an error of -ENOMEDIUM so there's no ambiguity." Of course, that's a silly example... but it's precisely where it sounds like you're going, from the above citation :) --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-iXXjXMGijvcU5WIG3Rrn Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEeAw ggXiMIIDyqADAgECAhBrp4p9CteI1lEK+Vnk57ThMA0GCSqGSIb3DQEBCwUAMH0xCzAJBgNVBAYT AklMMRYwFAYDVQQKEw1TdGFydENvbSBMdGQuMSswKQYDVQQLEyJTZWN1cmUgRGlnaXRhbCBDZXJ0 aWZpY2F0ZSBTaWduaW5nMSkwJwYDVQQDEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTAeFw0xNTEyMTYwMTAwMDVaFw0zMDEyMTYwMTAwMDVaMHUxCzAJBgNVBAYTAklMMRYwFAYDVQQK Ew1TdGFydENvbSBMdGQuMSkwJwYDVQQLEyBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0 eTEjMCEGA1UEAxMaU3RhcnRDb20gQ2xhc3MgMSBDbGllbnQgQ0EwggEiMA0GCSqGSIb3DQEBAQUA 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