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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,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 AE15EC433E1 for ; Sat, 15 Aug 2020 22:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83A56205CB for ; Sat, 15 Aug 2020 22:04:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bI9yTul+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729840AbgHOWE1 (ORCPT ); Sat, 15 Aug 2020 18:04:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728556AbgHOVvC (ORCPT ); Sat, 15 Aug 2020 17:51:02 -0400 Received: from mail-qt1-x831.google.com (mail-qt1-x831.google.com [IPv6:2607:f8b0:4864:20::831]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CCDCC06134C; Fri, 14 Aug 2020 18:33:15 -0700 (PDT) Received: by mail-qt1-x831.google.com with SMTP id e5so8359915qth.5; Fri, 14 Aug 2020 18:33:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=vJ/jVWhGTXG1e9E+PiLPXFME4LoN6xMadImJ1YD9YHU=; b=bI9yTul+XenFvqeVlqilZ/1PwJ1K3UFEioFw2tHq8PaWt4T8LWxVgwRJSMMkhCUE6S Mhk+1TtNGS6OWGrlFWUOTVc0gMvTT5rGsqPSPF7y7J9R5EjAKpFUxmIDn1hRIQ/wtohD h7ryjmhJ5t+sRCgBkpOsNhDqwsFM230xxiBOLSfm+c/bPJD3fF/amzVpL35ZoJJDtLUI yPPUOToH6zKsZZ56/pzJ3TtCqrkDl5KRjH98qkAEoQJehZkYfRWLA6mKX6g7SAAlM2p+ hM1RQv8oPv1ZMBB3K1KLvw53CeRFVuV+sLMvOML/8vh1qbpqShRfnoqCIec5DNVLUsfr Eb2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=vJ/jVWhGTXG1e9E+PiLPXFME4LoN6xMadImJ1YD9YHU=; b=rw635h449WWyb2LdxXwhLh6f64LaB/PGG829ylZXHG7wbg42YpTQR4jvlJDrDXhEzp 1SogV3Ph9t+bxew3WgQxmyt4KwUNq0fLDl92SOTzzLnj3eJ4tuwyGSZUZyz9EnFvANPK fWvB8RVa63Q+WHO7l9zS/RmCbE1vnr2AFXJlvQ6hXpxc/atZh1lkrpMDYkxFMDO5wwg2 pkEmKCPzXZi2wqvWKwrDd78Ta/hJ9mBOwxsM3bIzeZIUKhbtYaj2ENTvqTsBWlp5XYjx JpaUeN/ykWSk1vJLkYdN1rPR6ZtliiGz3BvOAcJZr9VY63vsgICUgwR0XBY7U1b0evt3 ROnQ== X-Gm-Message-State: AOAM531s2W0jywcll4pKZ6C8x19MKcPUaWOBCJ3YbP161lqYt8R9kO7B jMoOuxzxD4ZoRbKVkoVg01CGxoz2IoY= X-Google-Smtp-Source: ABdhPJzT7OzYhDt4EGcOfivsmmvRSIEn2XltAWy/5uJNgRq1XLSKbN6URmiVpoEPnEgK3HsV7HyH9Q== X-Received: by 2002:ac8:7405:: with SMTP id p5mr4604950qtq.308.1597455192803; Fri, 14 Aug 2020 18:33:12 -0700 (PDT) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id t69sm10061523qka.73.2020.08.14.18.33.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Aug 2020 18:33:12 -0700 (PDT) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Fri, 14 Aug 2020 21:33:10 -0400 To: Nick Desaulniers Cc: Andrew Morton , =?utf-8?B?RMOhdmlkIEJvbHZhbnNrw70=?= , Eli Friedman , stable@vger.kernel.org, Sami Tolvanen , Joe Perches , Tony Luck , Yury Norov , Daniel Axtens , Arvind Sankar , Dan Williams , "Joel Fernandes (Google)" , Andy Shevchenko , Kees Cook , Alexandru Ardelean , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Subject: Re: [PATCH] lib/string.c: implement stpcpy Message-ID: <20200815013310.GA99152@rani.riverdale.lan> References: <20200815002417.1512973-1-ndesaulniers@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200815002417.1512973-1-ndesaulniers@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 14, 2020 at 05:24:15PM -0700, Nick Desaulniers wrote: > +#ifndef __HAVE_ARCH_STPCPY > +/** > + * stpcpy - copy a string from src to dest returning a pointer to the new end > + * of dest, including src's NULL terminator. May overrun dest. > + * @dest: pointer to end of string being copied into. Must be large enough > + * to receive copy. > + * @src: pointer to the beginning of string being copied from. Must not overlap > + * dest. > + * > + * stpcpy differs from strcpy in two key ways: > + * 1. inputs must not overlap. > + * 2. return value is the new NULL terminated character. (for strcpy, the > + * return value is a pointer to src. > + */ > +#undef stpcpy > +char *stpcpy(char *__restrict__ dest, const char *__restrict__ src) > +{ > + while ((*dest++ = *src++) != '\0') > + /* nothing */; > + return dest; > +} > +#endif > + Won't this return a pointer that's one _past_ the terminating NUL? I think you need the increments to be inside the loop body, rather than as part of the condition. Nit: NUL is more correct than NULL to refer to the string terminator.