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* bug#65622: Inappropriate suppression of backtrace on an error
@ 2023-08-30 13:08 Alan Mackenzie
  2023-08-30 23:16 ` Michael Heerdegen
  0 siblings, 1 reply; 8+ messages in thread
From: Alan Mackenzie @ 2023-08-30 13:08 UTC (permalink / raw)
  To: 65622

Hello, Emacs.

On a recent master branch Emacs:
(i) emacs -Q
(ii) Insert the following into *scratch*:

(defmacro hash-if (condition then-form &rest else-forms)
  "A conditional compilation macro analogous to C's #if.
Evaluate CONDITION at macro-expansion time.  If it is non-nil,
expand the macro to THEN-FORM.  Otherwise expand it to ELSE-FORMS
enclosed in a `progn' form.  ELSE-FORMS may be empty."
  (declare (indent 2)
           (debug (form sexp &rest sexp)))
  (if (eval condition lexical-binding)
      then-form
    (cons 'progn else-forms)))

(defun foo (bar)
  (hash-if (< emacs-major-version 19)
      (car bar)
    (cons bar bar)))

(iii) Evaluate hash-if by putting point after it and doing C-x C-e.
(iv) Attempt to instrument foo for edebug by putting point inside foo and
  doing C-u C-M-x.  This throws the error: "Ignoring macroexpansion
  error: (void-function edebug-after)".
(v) Set debug-on-error to t with M-: (setq debug-on-error t).
(vi) Repeat (iv).  This throws the same error, without a backtrace.  This
  lack of a backtrace is a bug.
(vii) This backtrace is almost certainly being suppressed by a frivolous
  condition-case, whose main purpose appears to be making debugging more
  difficult.  ;-)
(viii) There would appear to be no justification for "ignoring" the error
  (void-function edebug-after).  Such error should not occur, and needs
  debugging.

-- 
Alan Mackenzie (Nuremberg, Germany).





^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2023-09-21 13:24 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-08-30 13:08 bug#65622: Inappropriate suppression of backtrace on an error Alan Mackenzie
2023-08-30 23:16 ` Michael Heerdegen
2023-08-31  7:41   ` Gerd Möllmann
2023-08-31  7:49     ` Eli Zaretskii
2023-08-31  8:21       ` Gerd Möllmann
2023-09-20 15:55   ` Alan Mackenzie
2023-09-21  1:44     ` Michael Heerdegen
2023-09-21 13:24       ` Alan Mackenzie

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