From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Philipp Stephani Newsgroups: gmane.emacs.bugs Subject: bug#41988: 28.0.50; Edebug unconditionally instruments definitions with &define specs Date: Sun, 9 Aug 2020 13:33:53 +0200 Message-ID: References: <20200621234816.88427.qmail@mail.muc.de> <20200808145948.GA10181@ACM> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="15286"; mail-complaints-to="usenet@ciao.gmane.io" Cc: 41988@debbugs.gnu.org To: Alan Mackenzie Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sun Aug 09 13:40:07 2020 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1k4jgN-0003qE-8G for geb-bug-gnu-emacs@m.gmane-mx.org; Sun, 09 Aug 2020 13:40:07 +0200 Original-Received: from localhost ([::1]:55362 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k4jgM-00021D-9t for geb-bug-gnu-emacs@m.gmane-mx.org; Sun, 09 Aug 2020 07:40:06 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:50668) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k4jbS-0000xs-2S for bug-gnu-emacs@gnu.org; Sun, 09 Aug 2020 07:35:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:48592) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1k4jbR-0003L0-P2 for bug-gnu-emacs@gnu.org; Sun, 09 Aug 2020 07:35:01 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1k4jbR-0003KG-MU for bug-gnu-emacs@gnu.org; Sun, 09 Aug 2020 07:35:01 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Philipp Stephani Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sun, 09 Aug 2020 11:35:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 41988 X-GNU-PR-Package: emacs Original-Received: via spool by 41988-submit@debbugs.gnu.org id=B41988.159697285212668 (code B ref 41988); Sun, 09 Aug 2020 11:35:01 +0000 Original-Received: (at 41988) by debbugs.gnu.org; 9 Aug 2020 11:34:12 +0000 Original-Received: from localhost ([127.0.0.1]:60138 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1k4jad-0003IG-LW for submit@debbugs.gnu.org; Sun, 09 Aug 2020 07:34:12 -0400 Original-Received: from mail-ot1-f54.google.com ([209.85.210.54]:33805) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1k4jab-0003I1-VD for 41988@debbugs.gnu.org; Sun, 09 Aug 2020 07:34:10 -0400 Original-Received: by mail-ot1-f54.google.com with SMTP id k12so5139775otr.1 for <41988@debbugs.gnu.org>; Sun, 09 Aug 2020 04:34:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=6fal7yEZr6AvDAgOfOLLinsHTt4+laJj/uoBiDOQWJQ=; b=QwwZ2Y/rv58PHS7+nMa2odXa7VwvpJDMjllr7wd+PbtEBNvo0h/FsNkeRMA6OnvWgb aEqTPi4fUQ+XIqnZ8xl6tssukstsxoF/FSU7VGEwTCMGfyA75s8HEe2h/I7P/ymAwPFR WMwkNkGshMatKCOqJ5qiuxkuGDnEwmLFsr0MMqBjLbmK6GJs5f4Ojqo1A+LBaP+YywJa drNf3mhdm0MIE3/x7YMFSktgnYowcg6EXcTybCXbXI95mhAtieXYeT0kgI+8hfFQN/XX 16npDqoH9Q9rihVTKSfnKRq2hw0xJ4QDCJlHmxBs0BsaKgsti7NofsBCrz0YhSm4MoVf vMpw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=6fal7yEZr6AvDAgOfOLLinsHTt4+laJj/uoBiDOQWJQ=; b=IcHNdRv4+xAA2i6uBbFnR/lqPE6pedyoFSyT8Nz1rtYCmXYBP3bqobKHw4nvfmkzWe 7lQdOINVfC4lckZa9rTKuuVR1K6mBeYKg1aoa5UkA4+5ai4EmW8JsFPzyemwV0ICfumF lixtlIKiJHPnz3w6h0FzdJ6O9f2UPyZJpVfwXjIRHIgsZ0PlTY7KsI2ny6HYmjcu1Dkx 6mC7IFlFlPMj7N3ao8aZTZwpeB86DSCwLprg82dhEzhkpLCy26+axMKrqtPb3oGH/mYj AAvtAS2o1620h503YRE7MZVSF3hQ9blMver6cmqS27HAUbZv/S7VQXshF9JRnWSMc21i Ak3Q== X-Gm-Message-State: AOAM531tfWUVXOO1iSWGw8XK3Adkk6uPSse/LAkT2GJ6Z/sLiclvRlO3 vkvrvS07HnrV8Pwpos4XO3ErkuXLw4jRMZUGDoRdLZG7 X-Google-Smtp-Source: ABdhPJzGDOHTdN878aNjY3oJDEns/jdUV/BzL2td+XunJnBk8W+YO/j6T5LKe85nVNTfnXNXAWtZvLdcKArZgL/KaQg= X-Received: by 2002:a9d:2203:: with SMTP id o3mr18292377ota.149.1596972844052; Sun, 09 Aug 2020 04:34:04 -0700 (PDT) In-Reply-To: <20200808145948.GA10181@ACM> X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list 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:184402 Archived-At: Am Sa., 8. Aug. 2020 um 16:59 Uhr schrieb Alan Mackenzie : > > Hello, Philipp. > > I must admit, I'm having difficulty understanding this problem. > > On Sat, Aug 08, 2020 at 13:01:50 +0200, Philipp Stephani wrote: > > Am Mo., 22. Juni 2020 um 01:48 Uhr schrieb Alan Mackenzie : > > > > In article you wrote: > > > > > As an example, edebug-instrument (C-u C-M-x) the following > > > > definition: > > > > > (defun bar () > > > > (cl-flet ((foo () 1)) > > > > (foo))) > > > > > The *Messages* buffer now says > > > > > Edebug: foo [2 times] > > > > Edebug: bar > > > > > Note the '[2 times]'. I believe this is because > > > > `edebug-match-&define' calls `edebug-make-form-wrapper' > > > > unconditionally. The Edebug spec for `cl-flet' has two `&or' > > > > branches that both use `&define', so if the first one doesn't match > > > > it will still create a definition using `edebug-make-form-wrapper'. > > > > Probably `edebug-match-&define' should only invoke > > > > `edebug-make-form-wrapper' if the specification actually matches. > > > > I don't understand why this is a bug. What precisely is wrong with > > > the messages displayed in *Messages*? Or is it something else which > > > is wrong? > > > > After instrumenting bar, can you actually step through it with > > > edebug? (I can't try it out myself, since I can't discern from the > > > documentation what, precisely, cl-flet is supposed to do.) > > > > So this is somewhat subtle, so let me try to give some context. The > > message is merely a symptom of defining a symbol twice (via > > edebug-make-form-wrapper). That's a problem when using Edebug for > > coverage instrumentation (in batch mode), as the coverage information > > is attached to properties of the symbol that Edebug > > generates/instruments. > > I'm trying to see what, exactly, this problem is. Edebug is defining a > symbol twice, once for each of two arms of a &or form in the edebug spec. > The first of these surely does nothing; it will eventually end up in the > garbage collector. The second will form the function slot of the symbol, > fulfilling all the Edebug things. What am I missing? The problem is that Edebug not only generates objects that would later be garbage-collected (and therefore not observable), but also modifies observable global state. This starts at https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-lisp/edebug.el?id=55bcb3f7e05c01d86778f1a2b7caccf72124614d#n1418 and continues for the rest of the edebug-make-form-wrapper function. In particular, https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-lisp/edebug.el?id=55bcb3f7e05c01d86778f1a2b7caccf72124614d#n1444 sets the `edebug' symbol property of the symbol being generated. None of these mutations are undone when backtracking. > > > Instrumenting a symbol with two different definitions can lead to very > > subtle bugs because the frequency vector and the form offset vector are > > out of sync, .... > > The picture you seem to be painting is of two distinct definitions being > assigned to the same symbol, and both of them being live. Do you have > any evidence that this is happening? Let's say it's rather an incompatible mixture of two definitions. https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41853 is a symptom of this. Another piece of evidence is the implementation of `edebug-make-form-wrapper': that function clearly modifies buffer contents and symbol properties even in branches that would later be discarded as part of backtracking. My (not well evidenced) assumption is that https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/emacs-lisp/edebug.el?id=55bcb3f7e05c01d86778f1a2b7caccf72124614d#n1427 regenerates the offset vector, but there's no regeneration of the frequency vector, which is the immediate trigger of https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41853, since now the frequency and offset vectors might be incompatible with each other. But I'd also assume the problem runs deeper: edebug-make-form-wrapper performs multiple mutations, and it's not really clear which of those are "safe" w.r.t. multiple definitions in not-taken branches. > > > .... see e.g. https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41853. > > Therefore it's important to prevent such duplicate instrumentation, > > typically by changing the Edebug symbol in some way (appending a unique > > suffix, etc.). Edebug does this already in many cases (ERT tests, CL > > methods, ...), but not always. For some more context, see the coverage > > instrumentation in my Bazel rules for ELisp > > (https://github.com/phst/rules_elisp). > > https://github.com/phst/rules_elisp/blob/master/elisp/ert/runner.el > > contains the ERT and coverage integration. In > > https://github.com/phst/rules_elisp/blob/0b24aa1660af2f6c668899bdd78aaba383d7ac18/elisp/ert/runner.el#L133-L134 > > I explicitly check for duplicate instrumentation. It is hard to predict > > in general whether a specific instance of duplicate instrumentation > > will lead to bugs like > > https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41853 or not, thus I'm > > treating every duplicate instrumentation as a bug. > > What exactly do you mean by "duplicate instrumentation"? If a symbol > gets defined twice, once for each arm of an &or in the edebug spec, does > that count as a duplicate instrumentation? What I mean concretely is evaluating `edebug-make-form-wrapper' (and therefore, mutating symbol properties and buffer contents) once for each branch of an &or construct.