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[198.84.214.74]) by smtp.gmail.com with ESMTPSA id h199sm12060047qke.112.2020.09.22.11.46.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Sep 2020 11:46:36 -0700 (PDT) Subject: Re: [RFC PATCH 0/3] implement dlmopen hooks for gdb To: Florian Weimer References: <20200626193228.1953-1-danielwa@cisco.com> <0f791d3a-20bc-4524-54eb-ce6df108fbff@redhat.com> <20200723184054.GD9875@zorba> <3ff42e45-b394-bf50-38c4-93baecc71497@redhat.com> <87h7rpwxke.fsf@oldenburg2.str.redhat.com> <87y2l1vhkn.fsf@oldenburg2.str.redhat.com> <87h7rpvgb4.fsf@oldenburg2.str.redhat.com> <4b05c127-573a-2e9b-1147-18f827bfd07c@redhat.com> <87r1qttzvu.fsf@oldenburg2.str.redhat.com> Organization: Red Hat Message-ID: Date: Tue, 22 Sep 2020 14:46:34 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <87r1qttzvu.fsf@oldenburg2.str.redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Carlos O'Donell via Libc-alpha Reply-To: Carlos O'Donell Cc: Pedro Alves , "xe-linux-external\(mailer list\)" , Carlos O'Donell via Libc-alpha , "Jeremy Stenglein \(jstengle\)" Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" On 9/22/20 2:44 PM, Florian Weimer wrote: > * Carlos O'Donell: > >> On 9/22/20 2:04 PM, Florian Weimer wrote: >>> * Carlos O'Donell: >>> >>>>> No, unlike GLIBC_PRIVATE, you can assume that if a GLIBC_DEBUG symbol is >>>>> there (and perhaps has the documented size), it has the documented >>>>> semantics. But you can't assume that it is present. >>>>> >>>>> The semantics of GLIBC_PRIVATE symbols can change arbitrarily, even >>>>> between builds. >>>> >>>> Yes, absolutely, I agree completely, for it to be useful the semantics >>>> have to be: >>>> >>>> - If you detect a given symbol foo@GLIBC_DEBUG, then the feature is >>>> present and has the semantics you expect. >>>> >>>> - If you want new semantics then you need to make a foo2@GLIBC_DEBUG >>>> with the new semantics. >>>> >>>> What are the runtime semantics of the symbol? How do you access it? >>> >>> That obviously depends on the symbol? Sorry, I don't quite understand >>> these questions. >> >> You noted "not intended to be used for run-time linking?" >> >> Could you expand on what you're thinking there? > > If there are no versioned dependencies on the symbol at the ELF level, > then the issues that require some distributions to backport whole symbol > sets do not apply. The exact contents of the GLIBC_DEBUG symbol set > does not matter than. Thank you for the clarification. I agree completely. -- Cheers, Carlos.