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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 93AA1C4321D for ; Thu, 23 Aug 2018 23:31:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5481021557 for ; Thu, 23 Aug 2018 23:31:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5481021557 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=perches.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726818AbeHXDDK (ORCPT ); Thu, 23 Aug 2018 23:03:10 -0400 Received: from smtprelay0174.hostedemail.com ([216.40.44.174]:57047 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726085AbeHXDDJ (ORCPT ); Thu, 23 Aug 2018 23:03:09 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay03.hostedemail.com (Postfix) with ESMTP id 7601E83777F0; Thu, 23 Aug 2018 23:31:11 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: ants85_a0a4471a2d42 X-Filterd-Recvd-Size: 5045 Received: from XPS-9350.home (unknown [47.151.153.53]) (Authenticated sender: joe@perches.com) by omf13.hostedemail.com (Postfix) with ESMTPA; Thu, 23 Aug 2018 23:31:08 +0000 (UTC) Message-ID: <1be357c91f6469c7a9b0e857fd15bad30347fd09.camel@perches.com> Subject: Re: [PATCH] include/linux/compiler*.h: make compiler-*.h mutually exclusive From: Joe Perches To: Nick Desaulniers Cc: Kees Cook , asmadeus@codewreck.org, Linus Torvalds , Masahiro Yamada , Jonathan Corbet , Arnd Bergmann , dwmw@amazon.co.uk, LKML , Thomas Gleixner , Will Deacon , Geert Uytterhoeven , Ingo Molnar , Andrew Morton , daniel@iogearbox.net, hpa@zytor.com Date: Thu, 23 Aug 2018 16:31:07 -0700 In-Reply-To: References: <20180822233724.110454-1-ndesaulniers@google.com> <20180823002508.GA822@nautica> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2018-08-23 at 16:12 -0700, Nick Desaulniers wrote: > On Thu, Aug 23, 2018 at 2:19 PM Joe Perches wrote: > > > > On Thu, 2018-08-23 at 14:03 -0700, Nick Desaulniers wrote: > > > One reply for a bunch of the various threads, to keep the number of emails down: > > > > > > On Wed, Aug 22, 2018 at 5:20 PM Joe Perches wrote: > > > > On Wed, 2018-08-22 at 16:37 -0700, Nick Desaulniers wrote: > > > > > +/* Compiler specific macros. */ > > > > > #ifdef __clang__ > > > > > #include > > > > > > > > probably better as > > > > > > > > #if defined(__clang) > > > > > > > > to match the style of the #elif defined()s below it > > > > > > Hi Joe, > > > Thanks for the feedback. I always appreciate it. If you have some > > > cleanups, want to send them to me, and I'll bundle them up for a PR? > > > I'm ok with that change. > > > > > > > > +#ifdef __GNUC_STDC_INLINE__ > > > > > +# define __gnu_inline __attribute__((gnu_inline)) > > > > > +#else > > > > > +# define __gnu_inline > > > > > +#endif > > > > > > > > Perhaps __gnu_inline should be in compiler-gcc and this > > > > should use > > > > > > > > #ifndef __gnu_inline > > > > #define __gnu_inline > > > > #endif > > > > > > Not this case; it's how we get gnu89 semantics for `extern inline` is > > > not compiler specific (therefor should not go in a compiler specific > > > header). > > > > It's not possible to know that compilers support what > > __attribute__(()) and at what version that support > > exists unless it is specified somewhere. > > __has_attribute: > https://clang.llvm.org/docs/LanguageExtensions.html#has-attribute > > The release notes of GCC-5 mention __has_attribute. > https://gcc.gnu.org/gcc-5/changes.html So not available in the now minimum supported gcc 4.6? > The point of feature detection is that it _doesn't matter_ what > version that support exists. Either it does and you can use it, or it > doesn't and you can decide whether to stop compiling or there's a > valid work around. > > Feature detection should be preferred to explicit version checks > except in 2 specific cases: > 1. It's not possible to properly perform feature detection. Language > features should not be added unless it's possible to safely check for > them. > 2. A very specific version of a very specific compiler is broken and > needs to be explicitly guarded against. > > > As far as I can tell, gnu_inline is not recognized by clang. > > > > https://clang.llvm.org/docs/AttributeReference.html > > If that was the case, I would not have added it in commit d03db2bc26f0 > ("compiler-gcc.h: Add __attribute__((gnu_inline)) to all inline > declarations"). > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d03db2bc26f0e4a6849ad649a09c9c73fccdc656 Hard to know. That commit message does not mention clang. > Docs can sometimes fall behind, the lone source of truth is the source code. > https://github.com/llvm-mirror/clang/search?q=gnu_inline&unscoped_q=gnu_inline Which no compiler user should have to read. > Godbolt is also incredibly helpful for testing various compiler versions: > https://godbolt.org/z/uMJ-mo Thanks for that. > https://reviews.llvm.org/D51190 That too. cheers, Joe