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Avoid duplicate Edebug symbols when backtracking (Bug#42701)

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When Edebug backtracks, it nevertheless generates definitions for the
non-matching branches, see Bug#41988 and Bug#42701.  This should be
fixed eventually (probably by deferring the definition until a branch
is known to match), but for now add a band-aid to avoid these
duplicate symbols, at least for anonymous forms.

* lisp/emacs-lisp/edebug.el (edebug-make-enter-wrapper): Regenerate
anonymous names.

* test/lisp/emacs-lisp/edebug-tests.el
(edebug-tests-duplicate-symbol-backtrack): New regression test.
This commit is contained in:
Philipp Stephani 2020-08-03 21:07:32 +02:00
parent 16b7f413a9
commit ca419812d3
2 changed files with 39 additions and 0 deletions
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7
lisp/emacs-lisp/edebug.el
View file

@ -1240,6 +1240,13 @@ purpose by adding an entry to this alist, and setting
;; since it wraps the list of forms with a call to `edebug-enter'.
;; Uses the dynamically bound vars edebug-def-name and edebug-def-args.
;; Do this after parsing since that may find a name.
(when (string-match-p (rx bos "edebug-anon" (+ digit) eos)
(symbol-name edebug-old-def-name))
;; FIXME: Due to Bug#42701, we reset an anonymous name so that
;; backtracking doesn't generate duplicate definitions. It would
;; be better to not define wrappers in the case of a non-matching
;; specification branch to begin with.
(setq edebug-old-def-name nil))
(setq edebug-def-name
(or edebug-def-name edebug-old-def-name (gensym "edebug-anon")))
`(edebug-enter

32
test/lisp/emacs-lisp/edebug-tests.el
View file

@ -1000,5 +1000,37 @@ clashes (Bug#41853)."
inner@cl-flet@10005
edebug-tests-cl-flet-2))))))
(ert-deftest edebug-tests-duplicate-symbol-backtrack ()
"Check that Edebug doesn't create duplicate symbols when
backtracking (Bug#42701)."
(with-temp-buffer
(dolist (form '((require 'subr-x)
(defun edebug-tests-duplicate-symbol-backtrack ()
(if-let (x (funcall (lambda (y) 1) 2)) 3 4))))
(print form (current-buffer)))
(let* ((edebug-all-defs t)
(edebug-initial-mode 'Go-nonstop)
(instrumented-names ())
(edebug-new-definition-function
(lambda (name)
(when (memq name instrumented-names)
(error "Duplicate definition of `%s'" name))
(push name instrumented-names)
(edebug-new-definition name)))
;; Make generated symbols reproducible.
(gensym-counter 10000))
(eval-buffer)
;; The anonymous symbols are uninterned. Use their names so we
;; can perform the assertion. The names should still be unique.
(should (equal (mapcar #'symbol-name (reverse instrumented-names))
;; The outer definition comes after the inner
;; ones because its body ends later.
;; FIXME: There are twice as many inner
;; definitions as expected due to Bug#42701.
;; Once that bug is fixed, remove the duplicates.
'("edebug-anon10000"
"edebug-anon10001"
"edebug-tests-duplicate-symbol-backtrack"))))))
(provide 'edebug-tests)
;;; edebug-tests.el ends here