From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 80287 invoked by alias); 7 Dec 2018 16:11:54 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 80237 invoked by uid 89); 7 Dec 2018 16:11:53 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-0.9 required=5.0 tests=BAYES_00,KAM_LAZY_DOMAIN_SECURITY,KAM_SHORT,SPF_HELO_PASS autolearn=no version=3.3.2 spammy=maintains, Pedro, pedro, Alves 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 ESMTP; Fri, 07 Dec 2018 16:11:51 +0000 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 612054E936; Fri, 7 Dec 2018 16:11:50 +0000 (UTC) Received: from [127.0.0.1] (ovpn04.gateway.prod.ext.ams2.redhat.com [10.39.146.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id C244D5EDE0; Fri, 7 Dec 2018 16:11:47 +0000 (UTC) Subject: Re: RFC: libiberty PATCH to disable demangling of ancient mangling schemes To: Jakub Jelinek , Nick Clifton References: <460cb971-0e21-1e3e-4920-8b3ee7290cf7@redhat.com> <736e8303-b724-f96d-54f5-46bff99fa34d@redhat.com> <57d33aa7-4e37-a09c-4bdc-974b5f654d33@redhat.com> <2928eac9-9363-ddb8-21eb-df878d2d4837@redhat.com> <20181207104011.GD12380@tucnak> Cc: Jason Merrill , Ian Lance Taylor , Richard Biener , matz@gcc.gnu.org, Scott Gayou , Tom Tromey , gcc-patches List , Binutils , GDB Patches From: Pedro Alves Message-ID: Date: Fri, 07 Dec 2018 16:11:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181207104011.GD12380@tucnak> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2018-12/txt/msg00478.txt.bz2 Adding gdb-patches, since demangling affects gdb. Ref: https://gcc.gnu.org/ml/gcc-patches/2018-12/msg00407.html On 12/07/2018 10:40 AM, Jakub Jelinek wrote: > On Fri, Dec 07, 2018 at 10:27:17AM +0000, Nick Clifton wrote: >>>> Looks good to me. Independently, do you see a reason not to disable the >>>> old demangler entirely? >>> >>> Like so. Does anyone object to this? These mangling schemes haven't >>> been relevant in decades. >> >> I am not really familiar with this old scheme, so please excuse my ignorance >> in asking these questions: >> >> * How likely is it that there are old toolchain in use out there that still >> use the v2 mangling ? Ie I guess that I am asking "which generation(s) >> of gcc used v2 mangling ?" > > GCC 3.0 and up used the new (Itanium C++ ABI) mangling, 2.95 and older used the old > mangling (2.96-RH used the new mangling I believe). > So you need compiler older than 17.5 years to have the old mangling. > Such a compiler didn't support most of the contemporarily used platforms > though at all (e.g. x86-64, powerpc64le, aarch64, I believe not even > powerpc64-linux). > Yeah. I guess the question would be whether it is reasonable to expect that people will still need to debug&inspect (with gdb, c++filt, etc.) any such old binary, and that they will need to do it with with modern tools, as opposed to sticking with older binutils&gdb, and how often would that be needed. I would say that it's very, very unlikely, and not worth it of the maintenance burden. Last I heard of 2.95-produced binaries I think was for some ancient gcc-2.95-based cross compiler that was still being minimally maintained, because it was needed to build&maintain some legacy stuff. That was maybe over 8 years ago, and it was off trunk. It's probably dead by now. And if isn't dead, whoever maintains the compiler off trunk certainly can also maintain old-ish binutils & gdb off trunk. Thanks, Pedro Alves