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=-7.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 B74E4C433DF for ; Sat, 15 Aug 2020 22:28:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A098020657 for ; Sat, 15 Aug 2020 22:28:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729028AbgHOW2i (ORCPT ); Sat, 15 Aug 2020 18:28:38 -0400 Received: from smtprelay0035.hostedemail.com ([216.40.44.35]:48322 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726598AbgHOW2i (ORCPT ); Sat, 15 Aug 2020 18:28:38 -0400 Received: from smtprelay.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by smtpgrave03.hostedemail.com (Postfix) with ESMTP id 8175C181CB2AE; Sat, 15 Aug 2020 03:42:39 +0000 (UTC) Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay01.hostedemail.com (Postfix) with ESMTP id 4721B100E7B6F; Sat, 15 Aug 2020 03:42:39 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: cry93_3b1331b27002 X-Filterd-Recvd-Size: 2703 Received: from XPS-9350.home (unknown [47.151.133.149]) (Authenticated sender: joe@perches.com) by omf13.hostedemail.com (Postfix) with ESMTPA; Sat, 15 Aug 2020 03:42:36 +0000 (UTC) Message-ID: Subject: Re: [PATCH v2] lib/string.c: implement stpcpy From: Joe Perches To: Nick Desaulniers , Andrew Morton Cc: =?ISO-8859-1?Q?D=E1vid_Bolvansk=FD?= , Eli Friedman , stable@vger.kernel.org, Arvind Sankar , Sami Tolvanen , Vishal Verma , Dan Williams , Andy Shevchenko , "Joel Fernandes (Google)" , Daniel Axtens , Kees Cook , Ingo Molnar , Yury Norov , Alexandru Ardelean , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Date: Fri, 14 Aug 2020 20:42:35 -0700 In-Reply-To: <20200815020946.1538085-1-ndesaulniers@google.com> References: <20200815014006.GB99152@rani.riverdale.lan> <20200815020946.1538085-1-ndesaulniers@google.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.4-0ubuntu1 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 Fri, 2020-08-14 at 19:09 -0700, Nick Desaulniers wrote: > LLVM implemented a recent "libcall optimization" that lowers calls to > `sprintf(dest, "%s", str)` where the return value is used to > `stpcpy(dest, str) - dest`. This generally avoids the machinery involved > in parsing format strings. Calling `sprintf` with overlapping arguments > was clarified in ISO C99 and POSIX.1-2001 to be undefined behavior. > > `stpcpy` is just like `strcpy` except it returns the pointer to the new > tail of `dest`. This allows you to chain multiple calls to `stpcpy` in > one statement. [] > diff --git a/include/linux/string.h b/include/linux/string.h [] > @@ -31,6 +31,9 @@ size_t strlcpy(char *, const char *, size_t); > #ifndef __HAVE_ARCH_STRSCPY > ssize_t strscpy(char *, const char *, size_t); > #endif > +#ifndef __HAVE_ARCH_STPCPY > +extern char *stpcpy(char *__restrict__, const char *__restrict__); If __restrict__ is used, perhaps it should follow the kernel style used by attributes like __iomem and __user extern char *stpcpy(char __restrict *dest, const char __restrict *src); (though I would lose the extern too) char *stpcpy(char __restrict *dest, const char __restrict *src);