From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 99689 invoked by alias); 1 Sep 2015 09:24:57 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 99677 invoked by uid 89); 1 Sep 2015 09:24:56 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.5 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,SPF_HELO_PASS,T_RP_MATCHES_RCVD autolearn=no version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Tue, 01 Sep 2015 09:24:55 +0000 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id 5F5CDC18F4D4 for ; Tue, 1 Sep 2015 09:24:54 +0000 (UTC) Received: from blade.nx (ovpn-116-114.ams2.redhat.com [10.36.116.114]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t819OpPv012043; Tue, 1 Sep 2015 05:24:52 -0400 Received: by blade.nx (Postfix, from userid 1000) id 4F9BA263030; Tue, 1 Sep 2015 10:24:49 +0100 (BST) Date: Tue, 01 Sep 2015 09:24:00 -0000 From: Gary Benson To: Sergio Durigan Junior Cc: GDB Patches Subject: Re: [PATCH 2/2] Catching errors on probes-based dynamic linker interface Message-ID: <20150901092449.GA6172@blade.nx> References: <1440200253-28603-1-git-send-email-sergiodj@redhat.com> <1440200253-28603-3-git-send-email-sergiodj@redhat.com> <20150824084255.GA16508@blade.nx> <87r3msd5xr.fsf@redhat.com> <20150825124748.GA6948@blade.nx> <87wpwjgrmt.fsf@redhat.com> <87lhcq7raj.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87lhcq7raj.fsf@redhat.com> X-IsSubscribed: yes X-SW-Source: 2015-09/txt/msg00006.txt.bz2 Sergio Durigan Junior wrote: > On Tuesday, August 25 2015, Sergio Durigan Junior wrote: > > Thanks for the review, Gary. > > Any more comments (from Gary or anyone else) before I go ahead and > apply this? I will wait until the end of tomorrow (Tuesday), and > then I'll go ahead. Sorry for the delay, I've been on PTO. > > On Tuesday, August 25 2015, Gary Benson wrote: > > > Sergio Durigan Junior wrote: > > > > On Monday, August 24 2015, Gary Benson wrote: > > > > > Maybe this would be clearer and more robust: > > > > > > > > > > TRY > > > > > { > > > > > unsigned probe_argc; > > > > > > > > > > probe_argc = get_probe_argument_count (pa->probe, frame); > > > > > > > > > > if (probe_argc == 2) > > > > > action = FULL_RELOAD; > > > > > else if (probe_argc < 2) > > > > > action = PROBES_INTERFACE_FAILED; > > > > > } > > > > > CATCH (ex, RETURN_MASK_ERROR) > > > > > { > > > > > exception_print (gdb_stderr, ex); > > > > > action = PROBES_INTERFACE_FAILED; > > > > > } > > > > > END_CATCH > > > > > > > > Maybe it's a matter of preference, but I don't like this (and > > > > I don't see why it is more robust). I prefer to have as > > > > little code as possible running on the TRY block, and handle > > > > everything else outside of it. I think it also makes things a > > > > bit more confuse because you have two places where action can > > > > be PROBES_INTERFACE_FAILED. > > > > > > Well, there are two different failures: > > > > > > 1) get_probe_argument_count failed > > > 2) get_probe_argument_count returned < 2 > > > > Yes, and both are covered by the proposed patch. It is not really > > important to distinguish between these failures today: what really > > matters is that GDB recognizes both as failures and acts > > accordingly. That matters. It also matters that future maintainers do not trip over this. I am ok with doing this: TRY { probe_argc = get_probe_argument_count (pa->probe, frame); } CATCH (ex, RETURN_MASK_ERROR) { exception_print (gdb_stderr, ex); probe_argc = 0; } END_CATCH If you put a big fat comment above the following block, e.g.: /* Note that failure of get_probe_argument_count will set probe_argc == 0. This must result in returning action = PROBES_INTERFACE_FAILED. */ if (probe_argc == 2) action = FULL_RELOAD; else if (probe_argc < 2) action = PROBES_INTERFACE_FAILED; But I would prefer it looked like this: if (probe_argc < 0) /* get_probe_argument_count failed */ action = PROBES_INTERFACE_FAILED else if (probe_argc == 2) action = FULL_RELOAD; else if (probe_argc < 2) /* we don't understand this probe with too few arguments */ action = PROBES_INTERFACE_FAILED; That's my preference because what is happening is documented by code (which is less likely to rot than comments). Either way is fine, but having one block of code setting probe_argc to zero and relying on a subsequent block of code then returning PROBES_INTERFACE_FAILED without anything to indicate that this is happening is not fine. Thanks, Gary -- http://gbenson.net/