bug#74771: Native compilation bug with struct predicates when lexical binding enabled (HEAD)

[Eric Marsden <eric.marsden@risk-engineering.org>]

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Hi,

With the attached source file, Emacs miscompiles the struct predicate such
that a repeated call to the predicate on a non-struct object returns t.
This occurs with current HEAD on Linux/AMD64, but not on the Emacs 30.0.92
pretest. It does not occur when the lexical binding cookie is not present.

% /opt/emacs/bin/emacs -Q --batch --eval "(load (native-compile \"/tmp/bug.el\"))" -f run
Loading /home/emarsden/.emacs.d/eln-cache/31.0.50-c021c983/bug-59c4b27c-c70072f9.eln (native compiled elisp)...
Running in GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.43, cairo version 1.18.2)
  of 2024-12-09
is? nil
is? t   ;; expecting nil
bar: 111


[-- Attachment #2: bug.el --]
[-- Type: text/x-emacs-lisp, Size: 409 bytes --]

;;;   -*- lexical-binding: t -*-
;;
;; /opt/emacs/bin/emacs -Q --batch -L . --eval "(load (native-compile \"/tmp/bug.el\"))" -f run

(require 'cl-lib)

(cl-defstruct foobles bar baz)

(defun bug (foo)
  (message "is? %s" (foobles-p foo))
  (message "is? %s" (foobles-p foo))
  (message "bar: %s" (foobles-bar foo)))

(defun run ()
  (message "Running in %s" (version))
  (let ((foo "foo"))
    (bug foo)))