From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?B?UmVuw6kgU2NoYXJmZQ==?= Subject: Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time Date: Wed, 27 Apr 2011 19:24:50 +0200 Message-ID: <4DB85162.6000204@lsrfire.ath.cx> References: <1303820660-744-1-git-send-email-pclouds@gmail.com> <7vaafdexsp.fsf@alter.siamese.dyndns.org> <4DB738A1.8020706@lsrfire.ath.cx> <7vhb9kd6kp.fsf@alter.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: =?UTF-8?B?Tmd1eeG7hW4gVGjDoWkgTmfhu41jIER1eQ==?= , git@vger.kernel.org To: Junio C Hamano X-From: git-owner@vger.kernel.org Wed Apr 27 19:25:48 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 1QF8Um-0007qa-7i for gcvg-git-2@lo.gmane.org; Wed, 27 Apr 2011 19:25:48 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756590Ab1D0RZn convert rfc822-to-quoted-printable (ORCPT ); Wed, 27 Apr 2011 13:25:43 -0400 Received: from india601.server4you.de ([85.25.151.105]:41228 "EHLO india601.server4you.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756236Ab1D0RZm (ORCPT ); Wed, 27 Apr 2011 13:25:42 -0400 Received: from [192.168.2.106] (p4FFDB579.dip.t-dialin.net [79.253.181.121]) by india601.server4you.de (Postfix) with ESMTPSA id 905212F8050; Wed, 27 Apr 2011 19:25:40 +0200 (CEST) User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 In-Reply-To: <7vhb9kd6kp.fsf@alter.siamese.dyndns.org> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Am 26.04.2011 23:51, schrieb Junio C Hamano: > Ren=C3=A9 Scharfe writes: >=20 >> How about something like this instead? The call to strbuf_grow() wa= s >> introduced in a8f3e2219 when there was no strbuf_slopbuf buffer that >> nowadays makes sure we always have a place to write an initial NUL. >> We can take it out again now, simplifying the code and hopefully >> avoiding future confusion. >=20 > Thanks; I think that makes sense. >=20 > It further may make sense to turn the assert into BUG() though, to cl= arify > what kind of programming error we are trying to catch. Perhaps like: >=20 >> static inline void strbuf_setlen(struct strbuf *sb, size_t len) { >> + assert(len< (sb->alloc ? sb->alloc : 1)); >=20 > if (len< (sb->alloc ? sb->alloc : 1)) > die("programming error: using strbuf_setlen() to extend a strbuf"); >=20 >> sb->len =3D len; >> sb->buf[len] =3D '\0'; >> } I like the idea, except the comparison needs to be inverted. Compiled, but not tested. The test suite takes too long and skips too many tests on my Windows box and I don't have any other machine available right now. :-/ -- >8 -- Subject: strbuf: clarify assertion in strbuf_setlen() Commit a8f3e2219 introduced the strbuf_grow() call to strbuf_setlen() t= o make ensure that there was at least one byte available to write the mandatory trailing NUL, even for previously unallocated strbufs. Then b315c5c0 added strbuf_slopbuf for the same reason, only globally f= or all uses of strbufs. Thus the strbuf_grow() call can be removed now. This avoids readers of strbuf.h from mistakenly thinking that strbuf_setlen() can be used to extend a strbuf. The following assert() needs to be changed to cope with the fact that sb->alloc can now be zero, which is OK as long as len is also zero. As suggested by Junio, use the chance to convert it to a die() with a shor= t explanatory message. The pattern of 'die("BUG: ...")' is already used = in strbuf.c. This was the only assert() in strbuf.[ch], so assert.h doesn't have to = be included anymore either. Signed-off-by: Rene Scharfe --- strbuf.h | 7 ++----- 1 files changed, 2 insertions(+), 5 deletions(-) diff --git a/strbuf.h b/strbuf.h index 07060ce..9e6d9fa 100644 --- a/strbuf.h +++ b/strbuf.h @@ -3,8 +3,6 @@ =20 /* See Documentation/technical/api-strbuf.txt */ =20 -#include - extern char strbuf_slopbuf[]; struct strbuf { size_t alloc; @@ -33,9 +31,8 @@ static inline size_t strbuf_avail(const struct strbuf= *sb) { extern void strbuf_grow(struct strbuf *, size_t); =20 static inline void strbuf_setlen(struct strbuf *sb, size_t len) { - if (!sb->alloc) - strbuf_grow(sb, 0); - assert(len < sb->alloc); + if (len > (sb->alloc ? sb->alloc - 1 : 0)) + die("BUG: strbuf_setlen() beyond buffer"); sb->len =3D len; sb->buf[len] =3D '\0'; } --=20 1.7.5