From 059f1863a268d6e9bd2c9b8e05e8546d4dd8f50b Mon Sep 17 00:00:00 2001
From: Alan Mackenzie <acm@muc.de>
Date: Wed, 30 Dec 2020 18:31:56 +0000
Subject: CC Mode: correct the handling of empty strings

In particular, have the macro cache invalidated after its last use in
c-before-change.

* lisp/progmodes/cc-langs.el (c-get-state-before-change-functions): Remove
c-invalidate-macro-cache from the entries it's in, moving it to....

* lisp/progmodes/cc-mode.el (c-before-change): Call c-invalidate-macro-cache
directly from the functions, after the call to c-invalidate-state-cache.
---
 lisp/progmodes/cc-langs.el | 2 --
 lisp/progmodes/cc-mode.el  | 6 +++++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/lisp/progmodes/cc-langs.el b/lisp/progmodes/cc-langs.el
index b10a085552d..c3cd81e1e82 100644
--- a/lisp/progmodes/cc-langs.el
+++ b/lisp/progmodes/cc-langs.el
@@ -457,13 +457,11 @@ so that all identifiers are recognized as words.")
 	c-before-change-check-raw-strings
 	c-before-change-check-<>-operators
 	c-depropertize-CPP
-	c-invalidate-macro-cache
 	c-truncate-bs-cache
 	c-before-change-check-unbalanced-strings
 	c-parse-quotes-before-change)
   (c objc) '(c-extend-region-for-CPP
 	     c-depropertize-CPP
-	     c-invalidate-macro-cache
 	     c-truncate-bs-cache
 	     c-before-change-check-unbalanced-strings
 	     c-parse-quotes-before-change)
diff --git a/lisp/progmodes/cc-mode.el b/lisp/progmodes/cc-mode.el
index 2f1885e5b61..d4c868dd1fc 100644
--- a/lisp/progmodes/cc-mode.el
+++ b/lisp/progmodes/cc-mode.el
@@ -2065,7 +2065,11 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
     ;; 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-invalidate-state-cache beg)
+    ;; The following must happen after the previous, which likely alters
+    ;; the macro cache.
+    (when c-opt-cpp-symbol
+      (c-invalidate-macro-cache beg end))))
 
 (defvar c-in-after-change-fontification nil)
 (make-variable-buffer-local 'c-in-after-change-fontification)
-- 
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