CC Mode: Restore string fence properties at each relevant external entry point

This fixes bug #55230.

* lisp/progmodes/cc-defs.el (c-string-fences-set-flag, c-with-string-fences):
New variable and macro.

* lisp/progmodes/cc-mode.el (c-called-from-text-property-change-p): Add
remove-text-properties to the list of accepted functions.
(c-clear-string-fences, c-restore-string-fences): Surround the functions'
innards with c-save-buffer-state to prevent text property changes causing
change functions to be called.
(c-before-change, c-after-change, c-font-lock-fontify-region): Replace the
explicit calls to c-restore-string-fences and c-clear-string-fences with
invocations of the new macro c-with-string-fences.

* lisp/progmodes/cc-awk.el (c-awk-extend-and-syntax-tablify-region)
(c-awk-end-of-defun)
* lisp/progmodes/cc-cmds.el (c-show-syntactic-information)
(c-electric-backspace, c-hungry-delete-backwards, c-electric-delete-forward)
(c-hungry-delete-forward, c-electric-pound, c-electric-brace)
(c-electric-slash, c-electric-star, c-electric-semi&comma, c-electric-colon)
(c-electric-lt-gt, c-electric-paren, c-beginning-of-defun, c-end-of-defun)
(c-display-defun-name, c-mark-function, c-beginning-of-statement)
(c-end-of-statement, c-indent-command, c-indent-exp, c-indent-defun)
(c-indent-line-or-region, c-fill-paragraph, c-indent-new-comment-line)
(c-context-line-break)
* lisp/progmodes/cc-guess.el (c-guess-region-no-install): These are all
"boundary" functions to CC Mode.  Surround each by c-with-string-fences.

1 files changed, 21 insertions, 0 deletions

diff --git a/lisp/progmodes/cc-defs.el b/lisp/progmodes/cc-defs.el
index a1270243550..54bedb4d9ca 100644
--- a/lisp/progmodes/cc-defs.el
+++ b/lisp/progmodes/cc-defs.el
@@ -1563,6 +1563,27 @@ with value CHAR in the region [FROM to)."
 	 (forward-char)))))
 
 
+;; Miscellaneous macro(s)
+(defvar c-string-fences-set-flag nil)
+;; Non-nil when we have set string fences with `c-restore-string-fences'.
+(defmacro c-with-string-fences (&rest forms)
+  ;; Restore the string fences, evaluate FORMS, then remove them again.  It
+  ;; should only be used at the top level of "boundary" functions in CC Mode,
+  ;; i.e. those called from outside CC Mode which directly or indirectly need
+  ;; unbalanced string markers to have their string-fence syntax-table text
+  ;; properties.  This includes all calls to `c-parse-state'.  This macro will
+  ;; be invoked recursively; however the `c-string-fences-set-flag' mechanism
+  ;; should ensure consistency, when this happens.
+  `(unwind-protect
+       (progn
+	 (unless c-string-fences-set-flag
+	   (c-restore-string-fences))
+	 (let ((c-string-fences-set-flag t))
+	   ,@forms))
+     (unless c-string-fences-set-flag
+       (c-clear-string-fences))))
+
+
 ;; Macros to put overlays (Emacs) or extents (XEmacs) on buffer text.
 ;; For our purposes, these are characterized by being possible to
 ;; remove again without affecting the other text properties in the