GNU bug report logs - #37540
[PATCH] Wishlist: Allow edebug-specs to signal arbitrary error strings on syntax errors in macros.

Previous Next

Full log

View this message in rfc822 format

From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Alan Mackenzie <acm <at> muc.de>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#37540: closed ([PATCH] Wishlist: Allow edebug-specs to signal
 arbitrary error strings on syntax errors in macros.)
Date: Fri, 17 Jan 2020 22:02:02 +0000

[Message part 1 (text/plain, inline)]

Your message dated Fri, 17 Jan 2020 22:01:43 +0000
with message-id <20200117220143.GA9769 <at> ACM>
and subject line Re: Bug 37540: [PATCH] Wishlist: Allow edebug-specs to signal arbitrary error strings on syntax errors in macros.
has caused the debbugs.gnu.org bug report #37540,
regarding [PATCH] Wishlist: Allow edebug-specs to signal arbitrary error strings on syntax errors in macros.
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
37540: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=37540
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Alan Mackenzie <acm <at> muc.de>
To: bug-gnu-emacs <at> gnu.org
Subject: [PATCH] Wishlist: Allow edebug-specs to signal arbitrary error
 strings on syntax errors in macros.
Date: Sat, 28 Sep 2019 12:30:34 +0000

Hello, Emacs.

I think it would be a good idea to allow edebug-specs to signal syntax
errors with arbitrary strings, like:

     ("`" &error "Too deeply nested backquotes")

.  The motivation is to complete the correction in bug #31090, which
fixed edebug's handling of nested backquotes in macros.

The problem with that fix is it doesn't handle triply nested backquotes
(without , or ,@ between them) at all well.  There is a fundamental
structure clash between backquote's nesting and Lisp's nesting of
parentheses.

The pragmatic solution is simply to ban triply nested backquotes (i.e.
three `s without ,s or ,@s between them) from edebug instrumentation.
However, this really needs a mechanism to output an error message
string.  There is currently no such mecahanism in edebug.

The following patch implements an &error mechanism in edebug.el, and
illustrates its use in the case which motivated it.

Any objections to committing this patch (together with the needed
amendments to documentation and NEWS)?




diff --git a/lisp/emacs-lisp/edebug.el b/lisp/emacs-lisp/edebug.el
index 717026995a..73257f1568 100644
--- a/lisp/emacs-lisp/edebug.el
+++ b/lisp/emacs-lisp/edebug.el
@@ -1683,6 +1683,7 @@ edebug-match-specs
                 (cl-macrolet-body . edebug-match-cl-macrolet-body)
 		(&not . edebug-match-&not)
 		(&key . edebug-match-&key)
+		(&error . edebug-match-&error)
 		(place . edebug-match-place)
 		(gate . edebug-match-gate)
 		;;   (nil . edebug-match-nil)  not this one - special case it.
@@ -1816,6 +1817,14 @@ edebug-match-&key
                            (car (cdr pair))))
 		 specs))))
 
+(defun edebug-match-&error (cursor specs)
+  ;; Signal an error, using the following string in the spec as argument.
+  (setq edebug-gate t)
+  (let* ((error-string (car specs)))
+    (if (stringp error-string)
+        (edebug-no-match cursor error-string)
+      (error "String expected after &error in edebug-spec"))))
+
 
 (defun edebug-match-gate (_cursor)
   ;; Simply set the gate to prevent backtracking at this level.
@@ -2185,6 +2194,8 @@ backquote-form
 
 (def-edebug-spec nested-backquote-form
   (&or
+   ("`" &error "Triply nested backquotes (without commas \"between\" them) \
+are too difficult to instrument")
    ;; Allow instrumentation of any , or ,@ contained within the (\, ...) or
    ;; (\,@ ...) matched on the next line.
    ([&or "," ",@"] backquote-form)


-- 
Alan Mackenzie (Nuremberg, Germany).

[Message part 3 (message/rfc822, inline)]

From: Alan Mackenzie <acm <at> muc.de>
To: 37540-done <at> debbugs.gnu.org
Cc: Eli Zaretskii <eliz <at> gnu.org>, Stefan Kangas <stefan <at> marxist.se>
Subject: Re: Bug 37540: [PATCH] Wishlist: Allow edebug-specs to signal
 arbitrary error strings on syntax errors in macros.
Date: Fri, 17 Jan 2020 22:01:43 +0000

Wishlist item committed to master.

-- 
Alan Mackenzie (Nuremberg, Germany).

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.