From owner-freebsd-hackers@FreeBSD.ORG Fri Mar 25 23:27:07 2011 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2BC24106566C; Fri, 25 Mar 2011 23:27:07 +0000 (UTC) (envelope-from delphij@gmail.com) Received: from mail-iy0-f182.google.com (mail-iy0-f182.google.com [209.85.210.182]) by mx1.freebsd.org (Postfix) with ESMTP id D453E8FC08; Fri, 25 Mar 2011 23:27:06 +0000 (UTC) Received: by iyj12 with SMTP id 12so1992802iyj.13 for ; Fri, 25 Mar 2011 16:27:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=BLJkaWJrj/QZnraupBMzmv94I3gu7f3EFUtQVrX10P4=; b=IETpx7iMdg9ixXcWmx9IvKd6fYe3I0Z8h8gzmM/uSzBHDwlo+JDMvDXN4Ku69JUI/x wAzSzXSDHrAE2QRIGoUY7oIcRWvkxXCtAm9BGayxwpSc2M6YNh4+do0r/WlTgUv/bZye 1LNhywL1fV4jkzvcSgXIm+e+vzBU/+RaftQbo= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=xp8BQMNjCdxG8kAgoE0XYOUtCmnTaoHx5U5j/zAIVcrBr1z/8nMBwHJTWT4Wd+UWhb jLaWr2rDdDUz14S6SJo70vrGMaoyzGuAYx9pcGm5yrD7rmL61qVMLsTsPE0zT/Grw5HV YT3u4f1fwSBTlHPd6q/y1WfqzQoEsvSUKh1gU= MIME-Version: 1.0 Received: by 10.231.194.195 with SMTP id dz3mr1369011ibb.148.1301095626294; Fri, 25 Mar 2011 16:27:06 -0700 (PDT) Received: by 10.231.143.209 with HTTP; Fri, 25 Mar 2011 16:27:06 -0700 (PDT) In-Reply-To: <20110325223203.GA95976@freebsd.org> References: <20110325002115.GA323@freebsd.org> <20110325015508.GA14565@freebsd.org> <20110325024658.GA19544@freebsd.org> <336A9ACD-29BF-41C9-BC25-917CC1E4587D@bsdimp.com> <20110325195325.GA69264@freebsd.org> <20110325223203.GA95976@freebsd.org> Date: Fri, 25 Mar 2011 16:27:06 -0700 Message-ID: From: Xin LI To: Alexander Best Content-Type: multipart/mixed; boundary=00504502cc8f9fc715049f56ee36 Cc: freebsd-hackers@freebsd.org Subject: Re: Switching to [KMGTPE]i prefixes? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Mar 2011 23:27:07 -0000 --00504502cc8f9fc715049f56ee36 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Fri, Mar 25, 2011 at 3:32 PM, Alexander Best wrote= : > On Fri Mar 25 11, Xin LI wrote: >> FYI I have a patch and I have incorporated some of Alexander's idea. >> >> Difference: >> >> =C2=A0- Use of both HN_DIVISOR_1000 and HN_IEC_PREFIXES triggers an >> assertion. =C2=A0I think it doesn't make sense to return since this is a= n >> API violation and we should just tell the caller explicitly; > > actually i vote for removing all asserts in humanize_number.c and return = -1 > based upon the later checks. > > the existing > > assert(buf !=3D NULL); > assert(suffix !=3D NULL); > > checks aren't really needed, since buf and suffix are also checked later = on. so > just having: Well, one of my believes is that a program should crash as early as possible, and with clear statement about "Why I crashed", when it's compiled with debugging aids, like assertions. To test or not to test these cases in a release binary on the other hand really depends on whether there is security or other bad implications. This generally makes developers' life easier, as they don't have to pursue into the code to find out why the program crashed, etc. Unlike system calls, humanize_number(3) does not indicate what's wrong via errno, e.g. it tells you "No I can't" rather than a reason of "Why I can't do that". Assertions here gives it an opportunity to say it loudly. If however the program is compiled with -DNDEBUG, these assertions would became no-op. At this stage, in my opinion, only basic tests should be done and we fall back to returning -1, or at least, not crash the program in a mysterious way. For this reasons, I think the assertion here against flags is right, it does not hurt if we proceed with both flags set, as we do not access undefined memory nor overwrite undefined memory. Furthermore, these values are more likely to be hard-wired at caller, where the assertion should catch the case. > =C2=A0 =C2=A0 =C2=A0 =C2=A0if (scale <=3D 0 || (scale >=3D maxscale && > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0(scale & (HN_AUTOSCALE | HN_GETS= CALE)) =3D=3D 0)) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return (-1); I think this one is good to have for both assertion and tests. Note that I think it should be scale < 0 here, scale =3D=3D 0 seems to be a valid value. > =C2=A0 =C2=A0 =C2=A0 =C2=A0if (buf =3D=3D NULL || suffix =3D=3D NULL) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return (-1); This duplication is necessary in my opinion. It's a protection against NULL pointer deference at runtime. > =C2=A0 =C2=A0 =C2=A0 =C2=A0if ((flags & (HN_DIVISOR_1000 | HN_IEC_PREFIXE= S)) =3D=3D 0) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return (-1); I'd vote no for this one for the reason above. >> =C2=A0- DIVISOR_1000 and !1000 cases use just same prefixes, so merge th= em >> while keeping divisor intact; > > good idea. however i think you should add a comment to point out that the > default behavior is !DIVISOR_1000 && !HN_IEC_PREFIXES. one has to look ve= ry > closely to find out. Will do. > #define HN_DECIMAL =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A00x01 > #define HN_NOSPACE =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A00x02 > #define HN_B =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A00x04 > #define HN_DIVISOR_1000 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0x08 > #define HN_IEC_PREFIXES =C2=A0 =C2=A0 =C2=A0 =C2=A0 0x40 > > #define HN_GETSCALE =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0x10 > #define HN_AUTOSCALE =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A00x20 Thinking again and I think we are just fine to use HN_IEC_PREFIXES =3D=3D 0x10 here. I don't think there is a reason why we can't use 0x10 for flags. Here is what in my mind. 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