(back_comment): Make sure we only consider comment-starters

of the relevant style and return -1 in case of a failure to find the
beginning of the comment.
(Fforward_comment): If back_comment fails, go back to the position just
after the comment-end.
(scan_lists): Add comment describing a very minor bug.

1 files changed, 23 insertions, 6 deletions

diff --git a/src/syntax.c b/src/syntax.c
index ceb48f3ec37..43f49dae9cf 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -508,6 +508,9 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
             code = Scomment;
           UPDATE_SYNTAX_TABLE_BACKWARD (from);
         }
+      else if (code == Scomment && comstyle != SYNTAX_COMMENT_STYLE (c))
+        /* Ignore comment starters of a different style.  */
+        continue;
 
       /* Ignore escaped characters, except comment-enders.  */
       if (code != Sendcomment && char_quoted (from, from_byte))
@@ -539,8 +542,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
         }
 
       if (code == Scomment)
-        /* FIXME: we should also check that the comstyle is correct
-           if the Scomment is a single-char. */
+        /* We've already checked that it is the relevant comstyle.  */
         {
           if (comnested && --nesting <= 0 && parity == 0 && !string_lossage)
             /* nested comments have to be balanced, so we don't need to
@@ -634,7 +636,7 @@ back_comment (from, from_byte, stop, comnested, comstyle, charpos_ptr, bytepos_p
   *charpos_ptr = from;
   *bytepos_ptr = from_byte;
 
-  return from;
+  return (from == comment_end) ? -1 : from;
 }
 
 DEFUN ("syntax-table-p", Fsyntax_table_p, Ssyntax_table_p, 1, 1, 0,
@@ -1795,6 +1797,8 @@ between them, return t; otherwise return nil.")
               INC_BOTH (from, from_byte);
               UPDATE_SYNTAX_TABLE_FORWARD (from);
             }
+          /* FIXME: here we ignore 2-char endcomments while we don't
+             when going backwards.  */
         }
       while (code == Swhitespace || code == Sendcomment);
 
@@ -1904,10 +1908,17 @@ between them, return t; otherwise return nil.")
             {
               found = back_comment (from, from_byte, stop, comnested, comstyle,
                                     &out_charpos, &out_bytepos);
-              if (found != -1)
-                from = out_charpos, from_byte = out_bytepos;
+              if (found == -1)
+                {
+                  /* Failure: we have to skip the one or two chars of the
+                     not-quite-endcomment.  */
+                  if (SYNTAX(c) != code)
+                    /* It was a two-char Sendcomment.  */
+                    INC_BOTH (from, from_byte);
+                  goto leave;
+                }
               /* We have skipped one comment.  */
-              break;
+              from = out_charpos, from_byte = out_bytepos;
             }
           else if (code != Swhitespace && code != Scomment)
             {
@@ -2227,6 +2238,12 @@ scan_lists (from, count, depth, sexpflag)
                 break;
               found = back_comment (from, from_byte, stop, comnested, comstyle,
                                     &out_charpos, &out_bytepos);
+              /* FIXME:  if found == -1, then it really wasn't a comment-end.
+                 For single-char Sendcomment, we can't do much about it apart
+                 from skipping the char.
+                 For 2-char endcomments, we could try again, taking both
+                 chars as separate entities, but it's a lot of trouble
+                 for very little gain, so we don't bother either.  -sm */
               if (found != -1)
                 from = out_charpos, from_byte = out_bytepos;
               break;