master f33b301c293: Fix syntax bugs involving escaped newlines in comments

[Alan Mackenzie]

branch: master
commit f33b301c29380cb0b295e1343e59c0faaf6ab621
Author: Alan Mackenzie <acm@muc.de>
Commit: Alan Mackenzie <acm@muc.de>

    Fix syntax bugs involving escaped newlines in comments
    
    This fixes bug#63535
    
    * src/syntax.c (forw_comment): take the initial syntax from the
    argument PREV_SYNTAX rather than checking the buffer position
    for a backslash.  Update the state at each character scanned.
    (scan_sexps_forward): When the end position is escaped after a
    call to forw_comment, return this status to the caller.
---
 src/syntax.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/syntax.c b/src/syntax.c
index 839ab36bb2f..0cac923bba7 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2323,13 +2323,16 @@ forw_comment (ptrdiff_t from, ptrdiff_t from_byte, 
ptrdiff_t stop,
          return 0;
        }
       c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
+      prev_syntax = syntax;
       syntax = SYNTAX_WITH_FLAGS (c);
       code = syntax & 0xff;
       if (code == Sendcomment
          && SYNTAX_FLAGS_COMMENT_STYLE (syntax, 0) == style
          && (SYNTAX_FLAGS_COMMENT_NESTED (syntax) ?
              (nesting > 0 && --nesting == 0) : nesting < 0)
-          && !(comment_end_can_be_escaped && char_quoted (from, from_byte)))
+          && !(comment_end_can_be_escaped
+              && ((prev_syntax & 0xff) == Sescape
+                  || (prev_syntax & 0xff) == Scharquote)))
        /* We have encountered a comment end of the same style
           as the comment sequence which began this comment
           section.  */
@@ -2353,7 +2356,11 @@ forw_comment (ptrdiff_t from, ptrdiff_t from_byte, 
ptrdiff_t stop,
           inc_both (&from, &from_byte);
           UPDATE_SYNTAX_TABLE_FORWARD (from);
           if (from == stop) continue; /* Failure */
-        }
+         c = FETCH_CHAR_AS_MULTIBYTE (from_byte);
+         prev_syntax = syntax;
+         syntax = Smax;
+         code = syntax;
+       }
       inc_both (&from, &from_byte);
       UPDATE_SYNTAX_TABLE_FORWARD (from);
 
@@ -3334,7 +3341,14 @@ do { prev_from = from;                           \
             are invalid now.  Luckily, the `done' doesn't use them
             and the INC_FROM sets them to a sane value without
             looking at them. */
-         if (!found) goto done;
+         if (!found)
+           {
+             if ((prev_from_syntax & 0xff) == Sescape
+                 || (prev_from_syntax & 0xff) == Scharquote)
+               goto endquoted;
+             else
+               goto done;
+           }
          INC_FROM;
          state->incomment = 0;
          state->comstyle = 0;  /* reset the comment style */