From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: pjb@informatimago.com (Pascal J. Bourguignon) Newsgroups: gmane.emacs.help Subject: Re: Problem advising nreverse. Date: Sat, 12 Dec 2009 13:18:55 +0100 Organization: Informatimago Message-ID: <87skbg8jww.fsf@galatea.local> References: NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1260621777 22577 80.91.229.12 (12 Dec 2009 12:42:57 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 12 Dec 2009 12:42:57 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sat Dec 12 13:42:49 2009 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1NJRJA-0002kw-GV for geh-help-gnu-emacs@m.gmane.org; Sat, 12 Dec 2009 13:42:49 +0100 Original-Received: from localhost ([127.0.0.1]:59447 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NJRJA-0006Iu-Ex for geh-help-gnu-emacs@m.gmane.org; Sat, 12 Dec 2009 07:42:48 -0500 Original-Path: news.stanford.edu!usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 57 Original-X-Trace: individual.net AY441D6BnUBIgEMt3I66OwlrFhc+aW0UYj5Dz8paNE3yARCfbn Cancel-Lock: sha1:MTliNjM2M2M1YTM0OTEyNDZhMTA4OGYxMjhiYzQ1NTc3NTM0MjBkZQ== sha1:iNMY2hw+ez6xgPbHJPAWudWo46o= Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en X-Disabled: X-No-Archive: no User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.3 (darwin) Original-Xref: news.stanford.edu gnu.emacs.help:175541 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:70618 Archived-At: Sergei Organov writes: > Hello, > > It seems that an advice set for `nreverse' function fails to be called > when `nreverse' is called from a byte compiled function: > > (let ((calls)) > (defun test (problem) > (setq calls (concat calls "[")) > (defun foo () (nreverse '())) > (and problem (byte-compile 'foo)) > (defadvice nreverse (before nrev-adv activate) > (setq calls (concat calls "nrev-adv"))) > (foo) > (ad-unadvise 'nreverse) > (setq calls (concat calls "]"))) > (test t) (test nil) (test t) > calls) > > Evaluating this gives me (in either GNU Emacs 22.2.1 or GNU Emacs 23.1.1): > > "[][nrev-adv][]" > > Is it bug or feature? What's going on here? Indeed, it is a feature. Advices are not available from several call points: 1- when the advised function is called from C code. 2- when the advised function is a an opcode of the virtual machine. You can observe the difference between the two primitives nreverse and buffer-name for example, with: (disassemble (byte-compile (lambda (x) (nreverse x)))) vs.: (disassemble (byte-compile (lambda (x) (buffer-name x)))) In the former case, nreverse is a byte code, and therefore no advice applies. In the later case, buffer-name is called with the call byte code, which will go thru the advice. Notice that if you really want to advice such a low level primitive function as nreverse, you can replace it with a lisp function (and recompile all the code that uses it). (defvar primitive-nreverse (symbol-function 'nreverse)) (defun nreverse (list) (funcall primitive-nreverse list)) Then nreverse will be a normal lisp function and you will be able to advise it. Be sure to recompile all the code that uses nreverse otherwise it will still shortcut to the primitive nreverse. -- __Pascal Bourguignon__