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bug#65017: 29.1; Byte compiler interaction with cl-lib function objects,
From: |
Stefan Monnier |
Subject: |
bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function |
Date: |
Thu, 03 Aug 2023 10:43:16 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
> We can simplify your nice little test case to
>
> ------- first file -----------
> (require 'cl-macs)
> (defun zeta () (cl-flet () #'equal))
> ------- second file ---------
> (defun eta () (cl-flet () (funcall #'equal 12 34)))
> ------------------------------
>
> and indeed, the leak is in cl--labels-convert-cache which will contain
> `equal` as a symbol-with-pos after byte-compiling the first file, and this
> causes trouble in the second file.
>
> cl--labels-convert-cache contains
>
> (#<symbol equal at 49> function #<symbol equal at 49>)
>
> and the function `eta` is consequently defined as
>
> (closure (t) nil (progn (#<symbol equal at 49> 12 34)))
>
> where 49 is the position of `equal` in the first file.
Thanks Mattias.
AFAICT the problem is that OT1H `symbols-with-pos-enabled` is
non-nil while loading the second file, but OTOH positions aren't
stripped from the resulting code.
So in `cl--labels-convert` when we check
(eq f (car cl--labels-convert-cache))
we get when `f` is just `equal` whereas the cache contains
the sympos, but that sympos is not stripped later on.
I don't know why `symbols-with-pos-enabled` is non-nil at that point (I
thought we only enabled it wile byte-compiling), but assuming there's
a good reason for it, I tried to work around the problem with the patch
below which is conceptually correct (indeed we should only return
(cdr cl--labels-convert-cache) only in the case where `f` is exactly
the very same object as (car cl--labels-convert-cache)).
Sadly, it doesn't seem to help for a reason that escapes me.
The *Messages* buffer says:
For information about GNU Emacs and the GNU system, type C-h C-a.
Compiling .../tmp/foo1.el...
Self-rewrite #<symbol equal at 82> to #'#<symbol equal at 82> (t)
Compiling .../tmp/foo1.el...done
Wrote .../tmp/foo1.elc
Self-rewrite equal to #'#<symbol equal at 82> (t)
Self-rewrite #<symbol equal at 82> to #'#<symbol equal at 82> (t)
where the middle "self-rewrite" is the culprit.
Apparently
(let ((symbols-with-pos-enabled nil))
(eq f (car cl--labels-convert-cache)))
returned non-nil when `f` was the bare `equal` and the `car` returned
the sympos. How can that be? I thought `eq` should really be the
good old "pointer equality" when `symbols-with-pos-enabled` is nil.
What am I missing?
Stefan
diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 0a3181561bd..bc71f565f3b 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -2037,7 +2039,12 @@
;; *after* handling `function', but we want to stop macroexpansion from
;; being applied infinitely, so we use a cache to return the exact `form'
;; being expanded even though we don't receive it.
- ((eq f (car cl--labels-convert-cache)) (cdr cl--labels-convert-cache))
+ ((let ((symbols-with-pos-enabled nil))
+ (eq f (car cl--labels-convert-cache)))
+ (let ((print-symbols-bare nil))
+ (message "Self-rewrite %S to %S (%S)" f (cdr cl--labels-convert-cache)
+ symbols-with-pos-enabled))
+ (cdr cl--labels-convert-cache))
(t
(let* ((found (assq f macroexpand-all-environment))
(replacement (and found
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Eric Marsden, 2023/08/02
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Mattias Engdegård, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function,
Stefan Monnier <=
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Mattias Engdegård, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Stefan Monnier, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Mattias Engdegård, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Mattias Engdegård, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Alan Mackenzie, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Stefan Monnier, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Alan Mackenzie, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Stefan Monnier, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Alan Mackenzie, 2023/08/03
- bug#65017: 29.1; Byte compiler interaction with cl-lib function objects, removes symbol-function, Stefan Monnier, 2023/08/03