From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.bugs Subject: bug#40671: [DOC] modify literal objects Date: Tue, 28 Apr 2020 17:04:59 -0700 Organization: UCLA Computer Science Department Message-ID: References: <530d3597-aaaa-f019-bafa-8229d13e7248@yandex.ru> <60b88f52-c50d-c57a-9ce5-495e6157d36e@cs.ucla.edu> <0721d8c1-4fe3-335c-7dbc-171487cb648a@yandex.ru> <6d1015da-0dc1-376c-f84b-5e3ee3149213@cs.ucla.edu> <286139d2-bbe1-2d5a-bec1-f781666376f1@yandex.ru> <10b89e6f-6fa6-f855-65b6-3361a74472d3@cs.ucla.edu> <8542efe2-c4a6-1da5-2513-7ffcaa6c4ec9@yandex.ru> <293d0eab-4617-08fe-aafa-d6841a750af0@cs.ucla.edu> <4085994e-f42d-b90f-9c86-ad42689bbff2@yandex.ru> <9cfc3b63-7df6-145a-8a78-e3320b6d3861@cs.ucla.edu> <72399223-0ab5-dbe4-5027-d929450a4df0@yandex.ru> <1a2d0454-baa4-9831-0e2c-4411eda1c2fe@yandex.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Injection-Info: ciao.gmane.io; 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Tue, 28 Apr 2020 17:04:59 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id Qu6DWBQfRUZJ; Tue, 28 Apr 2020 17:04:59 -0700 (PDT) Original-Received: from [192.168.1.9] (cpe-23-242-74-103.socal.res.rr.com [23.242.74.103]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 8452A160059; Tue, 28 Apr 2020 17:04:59 -0700 (PDT) Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCgptUUlOQkV5QWNtUUJFQURB QXlIMnhvVHU3cHBHNUQzYThGTVpFb243NGRDdmM0K3ExWEEySjJ0QnkycHdhVHFmCmhweHhk R0E5Smo1MFVKM1BENGJTVUVnTjh0TFowc2FuNDdsNVhUQUZMaTI0NTZjaVNsNW04c0thSGxH ZHQ5WG0KQUF0bVhxZVpWSVlYL1VGUzk2ZkR6ZjR4aEVtbS95N0xiWUVQUWRVZHh1NDd4QTVL aFRZcDVibHRGM1dZRHoxWQpnZDdneDA3QXV3cDdpdzdlTnZub0RUQWxLQWw4S1lEWnpiRE5D UUdFYnBZM2VmWkl2UGRlSStGV1FONFcra2doCnkrUDZhdTZQcklJaFlyYWV1YTdYRGRiMkxT MWVuM1NzbUUzUWpxZlJxSS9BMnVlOEpNd3N2WGUvV0szOEV6czYKeDc0aVRhcUkzQUZINmls QWhEcXBNbmQvbXNTRVNORnQ3NkRpTzFaS1FNcjlhbVZQa25qZlBtSklTcWRoZ0IxRApsRWR3 MzRzUk9mNlY4bVp3MHhmcVQ2UEtFNDZMY0ZlZnpzMGtiZzRHT1JmOHZqRzJTZjF0azVlVThN Qml5Ti9iClowM2JLTmpOWU1wT0REUVF3dVA4NGtZTGtYMndCeHhNQWhCeHdiRFZadWR6eERa SjFDMlZYdWpDT0pWeHEya2wKakJNOUVUWXVVR3FkNzVBVzJMWHJMdzYrTXVJc0hGQVlBZ1Jy NytLY3dEZ0JBZndoU In-Reply-To: Content-Language: en-US X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-Received-From: 209.51.188.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:179261 Archived-At: On 4/28/20 4:53 PM, Dmitry Gutov wrote: > const object - an object whose type is const-qualified, or a non-mutable > subobject of a const object. Such object _cannot_ be modified: attempt to do so > directly is a _compile-time error_, and attempt to do so indirectly (e.g., by > modifying the const object through a reference or pointer to non-const type) > results in undefined behavior. It's reasonable to have compile-time checking in a statically-typed language, though (as the above quote notes) the checking isn't adequate for C++ and one can get undefined behavior anyway in that language. And we could add some similar compile-time checking for the Elisp byte-compiler: it could warn about misuses like (aset "abc" 0 ?d), for example. However, any such compile-time checking would be either too restrictive (with false positives) or only partial (with false negatives) or both (as in C++). So it wouldn't be an adequate substitute for documenting that some objects should not be changed. > I gave a couple of options. I recall your using "literal object" but that's not a good choice of wording because the problem can occur with objects that are not literally present in any source code. >> there's clear precedent >> elsewhere for the terminology now in use in the emacs-27 manual. > > Any particular example? By "elsewhere" I meant in other language documentation (C/C++/etc.), not elsewhere in the emacs-27 manual.