From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 41960 invoked by alias); 1 Sep 2015 03:27:26 -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 41890 invoked by uid 89); 1 Sep 2015 03:27:20 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.3 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 03:27:18 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id 27273461C0 for ; Tue, 1 Sep 2015 03:27:17 +0000 (UTC) Received: from localhost (unused-10-15-17-51.yyz.redhat.com [10.15.17.51]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t813RG2M006236 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 31 Aug 2015 23:27:16 -0400 From: Sergio Durigan Junior To: Gary Benson Cc: GDB Patches Subject: Re: [PATCH 2/2] Catching errors on probes-based dynamic linker interface 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> X-URL: http://blog.sergiodj.net Date: Tue, 01 Sep 2015 03:27:00 -0000 In-Reply-To: <87wpwjgrmt.fsf@redhat.com> (Sergio Durigan Junior's message of "Tue, 25 Aug 2015 14:16:58 -0400") Message-ID: <87lhcq7raj.fsf@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-IsSubscribed: yes X-SW-Source: 2015-09/txt/msg00000.txt.bz2 On Tuesday, August 25 2015, I 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. Thanks, > 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. > >> I think it's more robust because, imagine a future where someone adds >> a zero-argument probe to glibc. They update the "if (probe_argc)..." >> block to allow zero-argument probes through. If get_probe_argument_count >> with such a GDB then it will not be treated as a failure. > > I think we should cross this bridge when we come to it. Plus, the > version you proposed does not take that scenario into account as well: > if probe_argc is zero, action will be PROBES_INTERFACE_FAILED; > therefore, this code would have to be rewritten anyway (in the scenario > you're proposing). > >> FWIW I also like to keep code in TRY blocks to a minimum. Maybe you >> could do it your original way, but set probe_argc to -1 in the CATCH >> and have the below block like: >> >> 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; >> >> It looks kind of silly but the compiler will optimize it out. > > This has crossed my mind when I was writing this part, but probe_argc is > unsigned int and therefore is never < 0. > > Moreover, as I said above, we are not really interested in > differentiating between the errors here; what we really want to know is > if there was an error. > >>> > As an aside it would clarify this code greatly if "old_chain" >>> > were renamed "disable_probes_interface" or similar. It took >>> > me a while to figure out what the code was doing, and I wrote >>> > it! >>> >>> Yeah. I'll leave this to another patch. >> >> I'll do it if you like (but I'll wait til you've got this through). > > Sure, no problem. > > Cheers, > > -- > Sergio > GPG key ID: 237A 54B1 0287 28BF 00EF 31F4 D0EB 7628 65FC 5E36 > Please send encrypted e-mail if possible > http://sergiodj.net/ -- Sergio GPG key ID: 237A 54B1 0287 28BF 00EF 31F4 D0EB 7628 65FC 5E36 Please send encrypted e-mail if possible http://sergiodj.net/