`cconv-closure-convert`, called from `byte-compile-preprocess` calls `setcar` on a self evaluating interactive form as part of the function body. This can be reproduced by adding the following snippet to `lisp/loadup.el`, and building Emacs: ``` (load "emacs-lisp/bytecomp") (setq sample-interactive-spec (purecopy '(interactive (list (if current-prefix-arg (prefix-numeric-value current-prefix-arg) 'toggle))))) (defmacro define-purecopied-func () `(defun foo-bar (arg) ,sample-interactive-spec)) (let ((byte-compile-debug t)) (byte-compile '(define-purecopied-func))) ``` (`purecopy` ensures mutating the list triggers a `pure_write_error`) As mutating quoted/constant lists is undefined behaviour as per the Elisp reference manual (https://www.gnu.org/software/emacs/manual/html_node/elisp/Mutability.htm ), the body returned by `macroexpand-all` should likely be copied using `copy-tree`. In GNU Emacs 30.0.50 (build 6, x86_64-pc-linux-gnu, GTK+ Version 3.24.36, cairo version 1.17.6) of 2023-01-05 built on vibhavp-mbp Repository revision: 15fc7b3cde92e420f48dfe188251e6af4d832af5 Repository branch: master System Description: Arch Linux Configured using: 'configure --with-pgtk --with-sqlite3 --with-native-compilation=yes --with-all --without-compress-install --enable-link-time-optimization -C 'CFLAGS=-march=native -mtune=native -O3 -g3 -ggdb3 -gdwarf-5'' Configured features: ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM GTK3 ZLIB Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: Lisp Interaction Minor modes in effect: tooltip-mode: t global-eldoc-mode: t eldoc-mode: t show-paren-mode: t electric-indent-mode: t mouse-wheel-mode: t tool-bar-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t blink-cursor-mode: t line-number-mode: t indent-tabs-mode: t transient-mark-mode: (only . t) auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t Load-path shadows: None found. Features: (shadow sort mail-extr emacsbug message mailcap yank-media puny dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068 epg-config gnus-util text-property-search time-date mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl- loaddefs comp comp-cstr warnings icons subr-x rx cl-seq cl-macs gv cl-extra help-mode bytecomp byte-compile cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel term/pgtk-win pgtk-win term/common-win pgtk-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic indonesian philippine cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european ethiopic indian cyrillic chinese composite emoji-zwj charscript charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp files window text-properties overlay sha1 md5 base64 format env code-pages mule custom widget keymap hashtable-print-readable backquote threads dbusbind inotify dynamic-setting system-font-setting font-render-setting cairo gtk pgtk lcms2 multi-tty make-network-process native-compile emacs) Memory information: ((conses 16 78180 10230) (symbols 48 7127 0) (strings 32 19480 1383) (string-bytes 1 595292) (vectors 16 16343) (vector-slots 8 326128 14214) (floats 8 28 51) (intervals 56 237 0) (buffers 984 11))