From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD58AC7618B for ; Wed, 24 Jul 2019 07:49:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D1DF21BF6 for ; Wed, 24 Jul 2019 07:49:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726379AbfGXHtf (ORCPT ); Wed, 24 Jul 2019 03:49:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49420 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725776AbfGXHte (ORCPT ); Wed, 24 Jul 2019 03:49:34 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3266F83F51; Wed, 24 Jul 2019 07:49:34 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-49.rdu2.redhat.com [10.10.120.49]) by smtp.corp.redhat.com (Postfix) with ESMTP id D378919C58; Wed, 24 Jul 2019 07:49:31 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <1563914986-26502-1-git-send-email-cai@lca.pw> References: <1563914986-26502-1-git-send-email-cai@lca.pw> To: Qian Cai Cc: dhowells@redhat.com, akpm@linux-foundation.org, davem@davemloft.net, arnd@arndb.de, jakub@redhat.com, ndesaulniers@google.com, morbo@google.com, jyknight@google.com, natechancellor@gmail.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] asm-generic: fix -Wtype-limits compiler warnings MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <31572.1563954571.1@warthog.procyon.org.uk> Date: Wed, 24 Jul 2019 08:49:31 +0100 Message-ID: <31573.1563954571@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 24 Jul 2019 07:49:34 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Qian Cai wrote: > Fix it by moving almost all of this multi-line macro into a proper > function __get_order(), and leave get_order() as a single-line macro in > order to avoid compilation errors. The idea was that you could compile-time initialise a global variable with get_order(): int a = get_order(SOME_MACRO); This is the same reason that ilog2() is a macro: int a = ilog2(SOME_MACRO); See the banner comment on get_order(): * This function may be used to initialise variables with compile time * evaluations of constants. If you're moving the constant branch into __get_order(), an inline function, then we'll no longer be able to do this and you need to modify the comment too. In fact, would there still be a point in having the get_order() macro? Also, IIRC, older versions of gcc see __builtin_constant_p(n) == 0 inside an function, inline or otherwise, even if the passed-in argument *is* constant. David