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[217.227.108.141]) by smtp.gmail.com with ESMTPSA id u16-20020aa7d990000000b00458ac4b4798sm650093eds.76.2022.10.06.21.34.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Oct 2022 21:34:32 -0700 (PDT) In-Reply-To: <87edvki88a.fsf@rfc20.org> (Matt Armstrong's message of "Thu, 06 Oct 2022 21:11:01 -0700") Received-SPF: pass client-ip=2a00:1450:4864:20::536; envelope-from=gerd.moellmann@gmail.com; helo=mail-ed1-x536.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:297137 Archived-At: Matt Armstrong writes: >> Clang libstd++ uses NULL, BTW, and I already wondered a little bit why. > > I believe GNU libstdc++ does not use sentinel nodes either. I have yet > to see see sentinel nodes used in an optimized tree implementation. I looked it up a few days ago, out of interest, and GCC's rb-tree uses sentinels, in Git master at least. Somewhere in this thread I posted where to look in GCC's Git repo, I can't remember ATM. (And I can't stop saying that it would be a big step forward for Emacs to allow C++. With std::multimap/std::multiset, we would have a ready-made complete solution for the tree, tested by a gazillion of users. Just dreaming :-)) > I think in the context of this overlay work the performance difference > is not very significant, since the code is doing a lot of other stuff > while traversing the tree. I agree. I think NULL could be better in multi-threaded cases, as Stefan alluded to.