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bug#53938: 27.2; Defining function that modifies cl-struct before defini
From: |
Ignacio Casso |
Subject: |
bug#53938: 27.2; Defining function that modifies cl-struct before defining cl-struct |
Date: |
Fri, 11 Feb 2022 10:45:50 +0100 |
User-agent: |
mu4e 1.6.10; emacs 27.2 |
Hello,
I've noticed a possible bug in Emacs.
If you define a function that uses a cl struct before defining the cl
struct (e.g., because the struct is defined in a package to be autoloaded and
the
function in your init file), there is an error when calling the function
later.
Here is a simple elisp file to reproduce it, starting Emacs with "emacs
-Q":
(require 'cl-macs)
(defun change-name (struct new-name)
(setf (my-struct-name struct) new-name))
(cl-defstruct my-struct
name)
(setq my-struct (make-my-struct))
(change-name my-struct "My struct")
This produces the following error:
Debugger entered--Lisp error: (void-function \(setf\ my-struct-name\))
(\(setf\ my-struct-name\) new-name v)
(let* ((v struct)) (\(setf\ my-struct-name\) new-name v))
change-name(#s(my-struct :name nil) "asdf")
eval((change-name my-struct "asdf") nil)
elisp--eval-last-sexp(nil)
eval-last-sexp(nil)
funcall-interactively(eval-last-sexp nil)
call-interactively(eval-last-sexp nil nil)
command-execute(eval-last-sexp)
A more realistic example, which produces the same error:
(defun my-package-config ()
(setf (package-struct-slot package-var) 'new-value))
(eval-after-load 'my-package '(my-package-config))
(cl-defstruct package-struct slot)
(defvar package-var (make-package-struct))
(provide 'my-package)
It does not work either if we use instead a form inside eval-after-load
instead of defining a function, as in this example:
(eval-after-load 'my-package '(setf (package-struct-slot package-var)
'new-value))
However, it does work if we do something like this:
(setq my-package-config '(setf (package-struct-slot package-var) 'new-value))
(eval-after-load 'my-package '(eval my-package-config))
I realize that this might be a design constraint given that this common
lisp feature is "emulated", but maybe it should be better documented or
produce more descriptive errors? It's a really uncommon case though, I
only encountered it trying to configure in a weird way mu4e which uses cl
structs.
Regards,
Ignacio
In GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.20)
of 2022-01-16 built on ignacio-IdeaPad-3-15ADA05
Windowing system distributor 'The X.Org Foundation', version 11.0.12013000
System Description: Ubuntu 20.04.3 LTS
- bug#53938: 27.2; Defining function that modifies cl-struct before defining cl-struct,
Ignacio Casso <=