Package: emacs;
Reported by: Philipp Stephani <p.stephani2 <at> gmail.com>
Date: Mon, 3 Aug 2020 16:48:02 UTC
Severity: normal
Found in version 28.0.50
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From: Philipp Stephani <p.stephani2 <at> gmail.com> To: 42701 <at> debbugs.gnu.org Subject: bug#42701: 28.0.50; Duplicate Edebug instrumentation of lambda form in some cases Date: Mon, 03 Aug 2020 18:47:28 +0200
Create a file /tmp/edebug.el: $ cat /tmp/edebug.el (defun f () (if-let (x (funcall (lambda (y) 1) 2)) 3 4)) Visit the file: $ emacs -Q -l subr-x -l edebug /tmp/edebug.el Now instrument the function `f' using C-u C-M-x. The *Messages* buffer will now contain Edebug: edebug-anon0 [2 times] Edebug: f The [2 times] indicates the problem: Edebug has instrumented two definitions with the same (generated) symbol. This is a problem when using Edebug for e.g. coverage instrumentation, as the coverage information is attached to the symbol itself (as a symbol property), and duplicate symbols when instrumenting code lead to subtle errors such as mismatching vector lengths for the position of the breakpoints and the hit counts. I'd speculate that this issue is similar to Bug#41988 in that Edebug defines instrumented symbols even when backtracking later. In this case, Edebug backtracks to the legacy (SYM VAL) form, but has already partially matched the ((SYM VAL)) form, including instrumenting the lambda form therein. I guess Edebug should perform some kind of two-phase instrumentation and instrument subforms only when a form has been chosen after backtracking. Since this is somewhat difficult to implement without rewriting larger parts of Edebug, it might be more feasible to regenerate anonymous symbols after a failed match. In GNU Emacs 28.0.50 (build 72, x86_64-pc-linux-gnu, GTK+ Version 3.24.18, cairo version 1.16.0) of 2020-08-03 Repository revision: 16b7f413a9ff819c374e07ee927c1fd2b4138109 Repository branch: master Windowing system distributor 'The X.Org Foundation', version 11.0.12008000 System Description: Debian GNU/Linux rodete Recent messages: For information about GNU Emacs and the GNU system, type C-h C-a. Configured using: 'configure --enable-gcc-warnings=warn-only --enable-gtk-deprecation-warnings --without-pop --with-mailutils --enable-checking=all --enable-check-lisp-object-type --with-modules 'CFLAGS=-O1 -ggdb3 -fno-omit-frame-pointer -fsanitize=address -fsanitize=undefined -fsanitize=pointer-compare -fsanitize=pointer-subtract'' Configured features: XPM JPEG TIFF GIF PNG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY LIBSELINUX GNUTLS FREETYPE HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD JSON PDUMPER Important settings: value of $LANG: en_US.utf8 value of $XMODIFIERS: @im=ibus locale-coding-system: utf-8-unix Major mode: Lisp Interaction Minor modes in effect: tooltip-mode: t global-eldoc-mode: t eldoc-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t line-number-mode: t transient-mark-mode: t Load-path shadows: None found. 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