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[217.227.99.31]) by smtp.gmail.com with ESMTPSA id lb7-20020a170906adc700b00a4479997b97sm6883994ejb.66.2024.03.06.20.28.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Mar 2024 20:28:04 -0800 (PST) In-Reply-To: (Paul Eggert's message of "Wed, 6 Mar 2024 12:32:35 -0800") Received-SPF: pass client-ip=2a00:1450:4864:20::632; envelope-from=gerd.moellmann@gmail.com; helo=mail-ej1-x632.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, T_SCC_BODY_TEXT_LINE=-0.01 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-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:316872 Archived-At: Paul Eggert writes: > On 2024-03-06 04:14, Eli Zaretskii wrote: >>> From: Gerd M=C3=B6llmann >>> >>> - Does someone remember the reasons why this has been done? > > Speed. It's significantly more efficient. > >>> - Is there something that relies on this? Maybe something that >>> relies on 0x0 being a valid Lisp_Object? > > Yes, these assumptions are present in other places. I tried to mark > all these places with "verify (NIL_IS_ZERO)" a decade ago, though I > wouldn't be surprised if I missed one or two at the time, or if other > dependencies have crept in since then (notably in src/comp.c, which I > haven't audited for this). Thanks, Paul. I've also looked around a bit yesterday, and my impression in the end was that making !NIL_IS_ZERO fly could easily be more work than trying to somehow marry it with the library I'm evaluating.