From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Why does byte-compile-file copy the input file to a different buffer? Date: Sun, 17 Dec 2023 17:09:28 +0000 Message-ID: References: <83cyv4kc67.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="15151"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Dec 17 18:10:13 2023 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1rEuea-0003iH-MZ for ged-emacs-devel@m.gmane-mx.org; Sun, 17 Dec 2023 18:10:12 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rEudz-0000AG-Jf; Sun, 17 Dec 2023 12:09:35 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rEudx-00009x-IW for emacs-devel@gnu.org; Sun, 17 Dec 2023 12:09:33 -0500 Original-Received: from mail.muc.de ([193.149.48.3]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rEudv-0004Ce-I9 for emacs-devel@gnu.org; Sun, 17 Dec 2023 12:09:33 -0500 Original-Received: (qmail 31749 invoked by uid 3782); 17 Dec 2023 18:09:28 +0100 Original-Received: from acm.muc.de (p4fe15b7c.dip0.t-ipconnect.de [79.225.91.124]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Sun, 17 Dec 2023 18:09:28 +0100 Original-Received: (qmail 4300 invoked by uid 1000); 17 Dec 2023 17:09:28 -0000 Content-Disposition: inline In-Reply-To: <83cyv4kc67.fsf@gnu.org> X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de Received-SPF: pass client-ip=193.149.48.3; envelope-from=acm@muc.de; helo=mail.muc.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-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:313932 Archived-At: Hello, Eli. On Sun, Dec 17, 2023 at 18:48:32 +0200, Eli Zaretskii wrote: > > Date: Sun, 17 Dec 2023 16:06:44 +0000 > > From: Alan Mackenzie > > On executing a byte-compile-file command, rather than working on the > > file's buffer directly, the byte compiler first copies the buffer/file > > into another buffer with a boring name like " *Compiler Input*" or " > > *Compiler Input*-1". > > Why does it do this? It makes it difficult, in the reader, to determine > > the identity of the actual source buffer. (Yes, I have reasons for > > wanting to do this.) > > Would it not be simpler just to compile directly from the source buffer, > > thus avoiding a needless copying and making it clear what the actual > > source buffer is? > The command uses insert-file-contents to insert the file into the > input buffer, and works on that, so that looks very natural to me. > I'm not sure what is bothering you in that, or why. >From inside the reader, the buffer " *Compiler Input*" is effectively anonymous: it gives no clue as to what the actual file or buffer is. If the byte compiler actually loaded the source file into a buffer with the normal name (e.g. bytecomp.el), that name would be available for use in the reader. Identifying the source presented to the reader is a difficult business. Quite bluntly, the code in lread.c is showing its age. Sometimes a file is loaded (and thus also read) by fragmented direct file access routines. Other times the reader is invoked from a file's buffer, other times from an anonymous buffer such as " *Compiler Input*". All I want is the name of the real buffer, or failing that, the name of the real file. When the reader sees " *Compiler Input*" does it have to assume that byte-compile-current-file is bound and use that? Even recognising " *Compiler Input*-1" in C code is difficult - there're no string functions in Emacs which can test that a given string is a prefix of another string. There's string-match, but it only works with a regular expression, not a plain string. By the time I put that sort of code into a C routine, it is so bulky, it drowns out the prime purpose of the routine. It's difficult. -- Alan Mackenzie (Nuremberg, Germany).