From 326ffcce5fbbb0ca368cfa08a33101dbbcaa2ace Mon Sep 17 00:00:00 2001
From: Alan Mackenzie
Date: Mon, 28 Dec 2015 16:01:05 +0000
Subject: 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'.
---
 src/syntax.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/syntax.c b/src/syntax.c
index 5b0ec6d071b..2acbd413858 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -790,8 +790,10 @@ back_comment (ptrdiff_t from, ptrdiff_t from_byte, ptrdiff_t stop,
 		   || SYNTAX_FLAGS_COMMENT_NESTED (syntax) != comnested))
 	continue;
 
-      /* Ignore escaped characters, except comment-enders.  */
-      if (code != Sendcomment && char_quoted (from, from_byte))
+      /* Ignore escaped characters, except comment-enders which cannot
+         be escaped.  */
+      if ((Vcomment_end_can_be_escaped || code != Sendcomment)
+          && char_quoted (from, from_byte))
 	continue;
 
       switch (code)
@@ -2346,7 +2348,8 @@ forw_comment (ptrdiff_t from, ptrdiff_t from_byte, ptrdiff_t stop,
       if (code == Sendcomment
 	  && SYNTAX_FLAGS_COMMENT_STYLE (syntax, 0) == style
 	  && (SYNTAX_FLAGS_COMMENT_NESTED (syntax) ?
-	      (nesting > 0 && --nesting == 0) : nesting < 0))
+	      (nesting > 0 && --nesting == 0) : nesting < 0)
+          && !(Vcomment_end_can_be_escaped && char_quoted (from, from_byte)))
 	/* We have encountered a comment end of the same style
 	   as the comment sequence which began this comment
 	   section.  */
@@ -3702,6 +3705,12 @@ character of that word.
 In both cases, LIMIT bounds the search. */);
   Vfind_word_boundary_function_table = Fmake_char_table (Qnil, Qnil);
 
+  DEFVAR_BOOL ("comment-end-can-be-escaped", Vcomment_end_can_be_escaped,
+               doc: /* Non-nil means an escaped ender inside a comment doesn'tend the comment.  */);
+  Vcomment_end_can_be_escaped = 0;
+  DEFSYM (Qcomment_end_can_be_escaped, "comment-end-can-be-escaped");
+  Fmake_variable_buffer_local (Qcomment_end_can_be_escaped);
+
   defsubr (&Ssyntax_table_p);
   defsubr (&Ssyntax_table);
   defsubr (&Sstandard_syntax_table);
-- 
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