--- Begin Message ---
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Subject: |
30.0.50; Phase out `cl-old-struct-compat-mode` |
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Date: |
Thu, 04 May 2023 13:51:09 -0400 |
Package: Emacs
Version: 30.0.50
`cl-old-struct-compat-mode` is a hideous hack I introduced back
in Emacs-26 when we switched CL structs from using plain vectors to
using the new `record` type. It provides some limited amount
of backward compatibility with code using `cl-defstruct` that was
compiled with 23<Emacs<26, at the cost of installing an advice on
`type-of` which tends to impact the performance of most
method dispatches in a non-trivial way.
I honestly don't know how much it's still used, so I propose the patch
below which declares that compatibility functionality as being obsolete,
and additionally emits a warning message *at run time* when it's used.
We usually keep our obsolescence message to compile time, but since this
is meant to detect the use of old `.elc` files, the relevant
compile-time is long past :-(
I also count on the fact that we still have a fair bit of time until
Emacs-30 is released, to discover that the run-time warning is too
annoying.
Any objection (beside the need to add a etc/NEWS message, obviously)?
Stefan
diff --git a/lisp/emacs-lisp/cl-lib.el b/lisp/emacs-lisp/cl-lib.el
index 7fee780a735..28d42cb69ab 100644
--- a/lisp/emacs-lisp/cl-lib.el
+++ b/lisp/emacs-lisp/cl-lib.el
@@ -560,6 +560,7 @@ cl-old-struct-compat-mode
(advice-add 'type-of :around #'cl--old-struct-type-of))
(t
(advice-remove 'type-of #'cl--old-struct-type-of))))
+(make-obsolete 'cl-old-struct-compat-mode nil "30.1")
(defun cl-constantly (value)
"Return a function that takes any number of arguments, but returns VALUE."
diff --git a/lisp/emacs-lisp/cl-preloaded.el b/lisp/emacs-lisp/cl-preloaded.el
index 9445093f143..da2780503b8 100644
--- a/lisp/emacs-lisp/cl-preloaded.el
+++ b/lisp/emacs-lisp/cl-preloaded.el
@@ -158,7 +158,9 @@ cl-struct-define
(cl-check-type name (satisfies cl--struct-name-p))
(unless type
;; Legacy defstruct, using tagged vectors. Enable backward compatibility.
- (cl-old-struct-compat-mode 1))
+ (with-suppressed-warnings ((obsolete cl-old-struct-compat-mode))
+ (message "cl-old-struct-compat-mode is obsolete!")
+ (cl-old-struct-compat-mode 1)))
(if (eq type 'record)
;; Defstruct using record objects.
(setq type nil))
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