CC Mode: Fix the timing of application and removal of string fence properties

This fixes bug #36897.

* lisp/progmodes/cc-mode.el (c-before-change-check-unbalanced-strings): Check
string fence text properties are actually present on string delimiters before
trying to remove them.
(c-before-change): Amend the nesting of unwind-protect, widen,
c-restore-string-fences, and c-clear-string-fences.  Move
invalidate-state-cache to outside of the widening.
(c-after-change): Amend the nesting of unwind-protect, widen,
c-restore-string-fences, and c-clear-string-fences.

1 files changed, 35 insertions, 36 deletions

diff --git a/lisp/progmodes/cc-mode.el b/lisp/progmodes/cc-mode.el
index 5e373b6e170..60a9de5ddb5 100644
--- a/lisp/progmodes/cc-mode.el
+++ b/lisp/progmodes/cc-mode.el
@@ -1426,8 +1426,11 @@ Note that the style variables are always made local to the buffer."
             (and c-multiline-string-start-char
                  (not (c-characterp c-multiline-string-start-char))))
       (when (and (eq end-literal-type 'string)
-                 (not (eq (char-before (cdr end-limits)) ?\()))
-        (c-remove-string-fences (1- (cdr end-limits)))
+                 (not (eq (char-before (cdr end-limits)) ?\())
+                 (memq (char-after (car end-limits)) c-string-delims)
+                 (equal (c-get-char-property (car end-limits) 'syntax-table)
+                        '(15)))
+        (c-remove-string-fences (car end-limits))
         (setq c-new-END (max c-new-END (cdr end-limits))))
 
       (when (and (eq beg-literal-type 'string)
@@ -1864,12 +1867,12 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
     ;; property changes.
     (when (fboundp 'syntax-ppss)
       (setq c-syntax-table-hwm most-positive-fixnum))
-    (unwind-protect
-        (progn
-          (c-restore-string-fences (point-min) (point-max))
-          (save-restriction
-            (save-match-data
-              (widen)
+    (save-restriction
+      (save-match-data
+        (widen)
+        (unwind-protect
+            (progn
+              (c-restore-string-fences (point-min) (point-max))
               (save-excursion
                 ;; Are we inserting/deleting stuff in the middle of an
                 ;; identifier?
@@ -1896,8 +1899,8 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
                                     'font-lock-comment-face)
                                 (previous-single-property-change end 'face))
                            end)))
-                  (when (>= end1 beg) ; Don't hassle about changes
-                                      ; entirely in comments.
+                  (when (>= end1 beg) ; Don't hassle about changes entirely in
+                                        ; comments.
                     ;; Find a limit for the search for a `c-type' property
                     (while
                         (and (/= (skip-chars-backward "^;{}") 0)
@@ -1924,12 +1927,11 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
                                 (buffer-substring-no-properties (point) type-pos)))
 
                         (goto-char end1)
-                        (skip-chars-forward "^;{}") ;FIXME!!! loop for
-                                                    ;comment, maybe
+                        (skip-chars-forward "^;{}") ; FIXME!!!  loop for
+                                        ; comment, maybe
                         (setq lim (point))
                         (setq term-pos
-                              (or (c-next-single-property-change end 'c-type nil lim)
-                                  lim))
+                              (or (c-next-single-property-change end 'c-type nil lim) lim))
                         (setq c-maybe-stale-found-type
                               (list type marked-id
                                     type-pos term-pos
@@ -1940,14 +1942,13 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
                 (if c-get-state-before-change-functions
                     (mapc (lambda (fn)
                             (funcall fn beg end))
-                          c-get-state-before-change-functions))
-                )))
-          ;; The following must be done here rather than in
-          ;; `c-after-change' because newly inserted parens would foul
-          ;; up the invalidation algorithm.
-          (c-invalidate-state-cache beg)
-          (c-truncate-lit-pos-cache beg))
-      (c-clear-string-fences))))
+                          c-get-state-before-change-functions))))
+          (c-clear-string-fences))))
+    (c-truncate-lit-pos-cache beg)
+    ;; The following must be done here rather than in `c-after-change'
+    ;; because newly inserted parens would foul up the invalidation
+    ;; algorithm.
+    (c-invalidate-state-cache beg)))
 
 (defvar c-in-after-change-fontification nil)
 (make-variable-buffer-local 'c-in-after-change-fontification)
@@ -1991,19 +1992,17 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
       ;; When `combine-after-change-calls' is used we might get calls
       ;; with regions outside the current narrowing.  This has been
       ;; observed in Emacs 20.7.
-      (unwind-protect
-          (progn
-            (c-restore-string-fences (point-min) (point-max))
-            (save-restriction
-              (save-match-data ; c-recognize-<>-arglists changes match-data
-                (widen)
-
+      (save-restriction
+        (save-match-data          ; c-recognize-<>-arglists changes match-data
+          (widen)
+          (unwind-protect
+              (progn
+                (c-restore-string-fences (point-min) (point-max))
                 (when (> end (point-max))
-                  ;; Some emacsen might return positions past the
-                  ;; end. This has been observed in Emacs 20.7 when
-                  ;; rereading a buffer changed on disk (haven't been
-                  ;; able to minimize it, but Emacs 21.3 appears to
-                  ;; work).
+                  ;; Some emacsen might return positions past the end. This
+                  ;; has been observed in Emacs 20.7 when rereading a buffer
+                  ;; changed on disk (haven't been able to minimize it, but
+                  ;; Emacs 21.3 appears to work).
                   (setq end (point-max))
                   (when (> beg end)
                     (setq beg end)))
@@ -2034,8 +2033,8 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
                 (save-excursion
                   (mapc (lambda (fn)
                           (funcall fn beg end old-len))
-                        c-before-font-lock-functions)))))
-        (c-clear-string-fences))))
+                        c-before-font-lock-functions)))
+            (c-clear-string-fences))))))
   ;; A workaround for syntax-ppss's failure to notice syntax-table text
   ;; property changes.
   (when (fboundp 'syntax-ppss)