From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Nieder Subject: Re: [PATCH 3/3] grep: get rid of useless x < 0 comparison on an enum member Date: Mon, 7 Nov 2011 13:49:13 -0600 Message-ID: <20111107194912.GA12469@elie.hsd1.il.comcast.net> References: <1320581184-4557-1-git-send-email-avarab@gmail.com> <1320581184-4557-4-git-send-email-avarab@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: git@vger.kernel.org, Junio C Hamano , Jim Meyering , Fredrik Gustafsson To: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason X-From: git-owner@vger.kernel.org Mon Nov 07 20:49:29 2011 Return-path: Envelope-to: gcvg-git-2@lo.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1RNVCC-0007PW-Vo for gcvg-git-2@lo.gmane.org; Mon, 07 Nov 2011 20:49:29 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753621Ab1KGTtY convert rfc822-to-quoted-printable (ORCPT ); Mon, 7 Nov 2011 14:49:24 -0500 Received: from mail-qw0-f46.google.com ([209.85.216.46]:34030 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753266Ab1KGTtX convert rfc822-to-8bit (ORCPT ); Mon, 7 Nov 2011 14:49:23 -0500 Received: by qao25 with SMTP id 25so967450qao.19 for ; Mon, 07 Nov 2011 11:49:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; bh=wkUSBKvfbQ+pylMABBP7vrch6nGYe+yUfUg0aPiBDFI=; b=ma01i72i8DSiqmDzNH9PiybOszYHHMDMaBW1+gmjSfrRhCU1dUmBfyE8McG2NQAB4y VPfTGKcLVDV0Z48/YBchyliVGRD8dvVxnD3HrjmIA2D4L+5+yRUTs7RuC3qfdnNK22jk Ed/hhGPDNI33xCuaMncVqloL5nbtEyJ1vs370= Received: by 10.229.246.5 with SMTP id lw5mr3291871qcb.93.1320695363019; Mon, 07 Nov 2011 11:49:23 -0800 (PST) Received: from elie.hsd1.il.comcast.net (c-24-1-56-9.hsd1.il.comcast.net. [24.1.56.9]) by mx.google.com with ESMTPS id cd3sm20740570qab.5.2011.11.07.11.49.21 (version=SSLv3 cipher=OTHER); Mon, 07 Nov 2011 11:49:21 -0800 (PST) Content-Disposition: inline In-Reply-To: <1320581184-4557-4-git-send-email-avarab@gmail.com> User-Agent: Mutt/1.5.21+46 (b01d63af6fea) (2011-07-01) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Hi, > --- a/grep.c > +++ b/grep.c > @@ -327,7 +327,7 @@ static struct grep_expr *prep_header_patterns(str= uct grep_opt *opt) > for (p =3D opt->header_list; p; p =3D p->next) { > if (p->token !=3D GREP_PATTERN_HEAD) > die("bug: a non-header pattern in grep header list."); > - if (p->field < 0 || GREP_HEADER_FIELD_MAX <=3D p->field) > + if (GREP_HEADER_FIELD_MAX <=3D p->field) I imagine the following would be less controversial. -- >8 -- =46rom: =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason Subject: grep: get rid of bounds check on "enum grep_header_field" valu= e The grep_header_field enum is defined as: enum grep_header_field { GREP_HEADER_AUTHOR =3D 0, GREP_HEADER_COMMITTER }; Git's grep code sanity-checks the value of p->field before using it in order to avoid reading and writing past the end of an array. Unfortunately that test trips up misguided static analyzers like "gcc -Wtype-limits" that do not recognize that C allows this enum to be a signed integer type and an "x < 0" comparison really could fire if someone passed in an uninitialized value. Let's just drop the check. Luckily git always does initialize p->field correctly, and if it were to stop doing so, then hopefully running the test suite with valgrind would catch it. Noticed with clang -Wtautological-compare. [jn: drop the GREP_HEADER_FIELD_MAX <=3D p->field check, too, for symmetry] Signed-off-by: =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason Signed-off-by: Jonathan Nieder --- grep.c | 2 -- 1 files changed, 0 insertions(+), 2 deletions(-) diff --git a/grep.c b/grep.c index b29d09c7..424c46cd 100644 --- a/grep.c +++ b/grep.c @@ -327,8 +327,6 @@ static struct grep_expr *prep_header_patterns(struc= t grep_opt *opt) for (p =3D opt->header_list; p; p =3D p->next) { if (p->token !=3D GREP_PATTERN_HEAD) die("bug: a non-header pattern in grep header list."); - if (p->field < 0 || GREP_HEADER_FIELD_MAX <=3D p->field) - die("bug: unknown header field %d", p->field); compile_regexp(p, opt); } =20 --=20 1.7.8.rc0