Allow line comments ending with escaped NL to be continued to the next line.

Use this in C, C++, and Objective C Modes.  Fixes bug#22246

* src/syntax.c (comment-end-can-be-escaped): New buffer local variable.
(forw-comment, back-comment): On encountering an end of comment character,
test whether it is escaped when `comment-end-can-be-escaped' is non-nil.

* doc/lispref/syntax.texi (Control Parsing): Describe
`comment-end-can-be-escaped'.

* etc/NEWS (Lisp Changes): Describe `comment-end-can-be-escaped'.

* lisp/progmodes/cc-langs.el: New c-lang-setvar `comment-end-can-be-escaped'.

1 files changed, 8 insertions, 0 deletions

diff --git a/lisp/progmodes/cc-langs.el b/lisp/progmodes/cc-langs.el
index 5b670833d45..1a07c4cd699 100644
--- a/lisp/progmodes/cc-langs.el
+++ b/lisp/progmodes/cc-langs.el
@@ -1433,6 +1433,14 @@ properly."
             "\\)\\s *"))
 (c-lang-setvar comment-start-skip (c-lang-const comment-start-skip))
 
+(c-lang-defconst comment-end-can-be-escaped
+  "When non-nil, escaped EOLs inside comments are valid.
+This works in Emacs >= 25.1."
+  t nil
+  (c c++ objc) t)
+(c-lang-setvar comment-end-can-be-escaped
+               (c-lang-const comment-end-can-be-escaped))
+
 (c-lang-defconst c-syntactic-ws-start
   ;; Regexp matching any sequence that can start syntactic whitespace.
   ;; The only uncertain case is '#' when there are cpp directives.