From owner-freebsd-arch@freebsd.org Mon May 28 20:07:40 2018 Return-Path: Delivered-To: freebsd-arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5B2DFF7F616 for ; Mon, 28 May 2018 20:07:40 +0000 (UTC) (envelope-from rpokala@freebsd.org) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 014408133F for ; Mon, 28 May 2018 20:07:40 +0000 (UTC) (envelope-from rpokala@freebsd.org) Received: by mailman.ysv.freebsd.org (Postfix) id B4758F7F611; Mon, 28 May 2018 20:07:39 +0000 (UTC) Delivered-To: arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A2203F7F610 for ; Mon, 28 May 2018 20:07:39 +0000 (UTC) (envelope-from rpokala@freebsd.org) Received: from smtp.freebsd.org (unknown [IPv6:2610:1c1:1:606c::24b:4]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "smtp.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 56CFA8133C; Mon, 28 May 2018 20:07:39 +0000 (UTC) (envelope-from rpokala@freebsd.org) Received: from [192.168.1.4] (c-73-241-240-124.hsd1.ca.comcast.net [73.241.240.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) (Authenticated sender: rpokala) by smtp.freebsd.org (Postfix) with ESMTPSA id BCDF717947; Mon, 28 May 2018 20:07:38 +0000 (UTC) (envelope-from rpokala@freebsd.org) User-Agent: Microsoft-MacOutlook/10.d.1.180523 Date: Mon, 28 May 2018 13:07:35 -0700 Subject: Re: To assert() or not to assert(), that is not really a question... From: Ravi Pokala To: Poul-Henning Kamp CC: Message-ID: <40636EBA-9D41-4F3E-8D10-3654E92FC6AA@panasas.com> Thread-Topic: To assert() or not to assert(), that is not really a question... References: <4514.1527319154@critter.freebsd.dk> <4427091E-3B0E-4C34-B4C6-3557DD7B55E4@panasas.com> <22469.1527531846@critter.freebsd.dk> In-Reply-To: <22469.1527531846@critter.freebsd.dk> Mime-version: 1.0 Content-type: text/plain; charset="UTF-8" Content-transfer-encoding: quoted-printable X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 May 2018 20:07:40 -0000 Interesting stuff. Thanks, phk! -Ravi (rpokala@) =EF=BB=BF-----Original Message----- From: Poul-Henning Kamp Date: 2018-05-28, Monday at 11:24 To: Ravi Pokala Cc: Subject: Re: To assert() or not to assert(), that is not really a question.= .. -------- In message <4427091E-3B0E-4C34-B4C6-3557DD7B55E4@panasas.com>, Ravi Pokala = writ es: >> 1. "Regular asserts" - things which are just plain wrong, which >> probably means we have a genuine bug somewhere. Examples could >> be null pointers where previous checks should have ensured this >> not be so. Also error situations for which there is no saner >> handling that killing the projcess. >>=20 >> ... >>=20 >> 3. "wrong asserts" - Internal state is messed up, program flow >> has taken a "impossible" branch. A good example is the >> default branch of a switch on a finite input set. > >Hi Poul-Henning, > >I am in strong overall agreement with your argument. I am however >confused as to how (1) and (3) are different; they're both irrevocably >bad internal state. The regular assert is assert() as we know and love it, and if it triggers it reports the C-source of the failing condition. The WRONG macro always triggers, and reports its string argument. Here is a random snippet of varnish code showing both: /* Per specification */ assert(sizeof vpx1_sig =3D=3D 5); assert(sizeof vpx2_sig =3D=3D 12); [...] p =3D req->htc->rxbuf_b; if (p[0] =3D=3D vpx1_sig[0]) i =3D vpx_proto1(wrk, req); else if (p[0] =3D=3D vpx2_sig[0]) i =3D vpx_proto2(wrk, req); else WRONG("proxy sig mismatch"); Poul-Henning PS: You can explore the Varnish source code here: https://github.com/varnishcache/varnish-cache Asserts defined in: .../include/vas.h Custom backtrace/state dump in: .../bin/varnishd/cache/cache_panic.c Code coverage results: http://varnish-cache.org/gcov/ You may also find the void-pointer paranoia interesting: .../include/miniobj.h --=20 Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe =20 Never attribute to malice what can adequately be explained by incompetence.