(scan_lists): Properly skip the comment-fence character

that ends a comment, when moving forward.
(Fbackward_prefix_chars): Return immediately if point is at BEGV.

(prev_char_comend_first): New function.
(back_comment): Use that.  Carefully update syntax table position
for each character that is fetched.
(Fforward_comment): Likewise.
(scan_lists): Likewise.
(prev_char_comstart_first): New function.

diff --git a/src/syntax.c b/src/syntax.c
index d043e115565aff4fc970f1a73f03f94eae7c3550..efa4bf3d271d2e856e8124716383f81e060e3003 100644 (file)
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -130,7 +130,7 @@ update_syntax_table (charpos, count, init, object)
       invalidate = 0;
       if (NULL_INTERVAL_P (i))
        return;
-      /* interval_of () updates only ->position of the return value,
+      /* interval_of updates only ->position of the return value, so
         update the parents manually to speed up update_interval.  */
       while (!NULL_PARENT (i)) 
        {
@@ -158,7 +158,7 @@ update_syntax_table (charpos, count, init, object)
   else if (charpos < i->position)              /* Move left.  */
     {
       if (count > 0)
-       error ("Error in syntax_table logic for intervals <-.");
+       error ("Error in syntax_table logic for intervals <-");
       /* Update the interval.  */
       i = update_interval (i, charpos);
       if (oldi->position != INTERVAL_LAST_POS (i))
@@ -172,7 +172,7 @@ update_syntax_table (charpos, count, init, object)
   else if (charpos >= INTERVAL_LAST_POS (i)) /* Move right.  */
     {
       if (count < 0)
-       error ("Error in syntax_table logic for intervals ->.");
+       error ("Error in syntax_table logic for intervals ->");
       /* Update the interval.  */
       i = update_interval (i, charpos);
       if (i->position != INTERVAL_LAST_POS (oldi))
@@ -394,6 +394,38 @@ find_defun_start (pos, pos_byte)
   return find_start_value;
 }
 \f
+/* Return the SYNTAX_COMEND_FIRST of the character before POS, POS_BYTE.  */
+
+static int
+prev_char_comend_first (pos, pos_byte)
+     int pos, pos_byte;
+{
+  int c, val;
+
+  DEC_BOTH (pos, pos_byte);
+  UPDATE_SYNTAX_TABLE_BACKWARD (pos);
+  c = FETCH_CHAR (pos_byte);
+  val = SYNTAX_COMEND_FIRST (c);
+  UPDATE_SYNTAX_TABLE_FORWARD (pos + 1);
+  return val;
+}
+
+/* Return the SYNTAX_COMSTART_FIRST of the character before POS, POS_BYTE.  */
+
+static int
+prev_char_comstart_first (pos, pos_byte)
+     int pos, pos_byte;
+{
+  int c, val;
+
+  DEC_BOTH (pos, pos_byte);
+  UPDATE_SYNTAX_TABLE_BACKWARD (pos);
+  c = FETCH_CHAR (pos_byte);
+  val = SYNTAX_COMSTART_FIRST (c);
+  UPDATE_SYNTAX_TABLE_FORWARD (pos + 1);
+  return val;
+}
+
 /* Checks whether charpos FROM is at the end of a comment.
    FROM_BYTE is the bytepos corresponding to FROM.
    Do not move back before STOP.
@@ -444,7 +476,7 @@ back_comment (from, from_byte, stop, comstyle, charpos_ptr, bytepos_ptr)
      that determines quote parity to the comment-end.  */
   while (from != stop)
     {
-      int temp_byte;
+      int temp_byte, prev_comend_second;
 
       /* Move back and examine a character.  */
       DEC_BOTH (from, from_byte);
@@ -456,23 +488,25 @@ back_comment (from, from_byte, stop, comstyle, charpos_ptr, bytepos_ptr)
       /* If this char is the second of a 2-char comment end sequence,
         back up and give the pair the appropriate syntax.  */
       if (from > stop && SYNTAX_COMEND_SECOND (c)
-         && (temp_byte = dec_bytepos (from_byte),
-             SYNTAX_COMEND_FIRST (FETCH_CHAR (temp_byte))))
+         && prev_char_comend_first (from, from_byte))
        {
          code = Sendcomment;
          DEC_BOTH (from, from_byte);
-         /* This is apparently the best we can do: */
          UPDATE_SYNTAX_TABLE_BACKWARD (from);
          c = FETCH_CHAR (from_byte);
        }
                        
       /* If this char starts a 2-char comment start sequence,
         treat it like a 1-char comment starter.  */
-      if (from < scanstart && SYNTAX_COMSTART_FIRST (c)
-         && (temp_byte = inc_bytepos (from_byte),
-             (SYNTAX_COMSTART_SECOND (FETCH_CHAR (temp_byte))
-              && comstyle == SYNTAX_COMMENT_STYLE (FETCH_CHAR (temp_byte)))))
-       code = Scomment;
+      if (from < scanstart && SYNTAX_COMSTART_FIRST (c))
+       {
+         temp_byte = inc_bytepos (from_byte);
+         UPDATE_SYNTAX_TABLE_FORWARD (from + 1);
+         if (SYNTAX_COMSTART_SECOND (FETCH_CHAR (temp_byte))
+             && comstyle == SYNTAX_COMMENT_STYLE (FETCH_CHAR (temp_byte)))
+           code = Scomment;
+         UPDATE_SYNTAX_TABLE_BACKWARD (from);
+       }
 
       /* Ignore escaped characters, except comment-enders.  */
       if (code != Sendcomment && char_quoted (from, from_byte))
@@ -1590,6 +1624,8 @@ between them, return t; otherwise return nil.")
     {
       do
        {
+         int comstart_first;
+
          if (from == stop)
            {
              SET_PT_BOTH (from, from_byte);
@@ -1599,9 +1635,11 @@ between them, return t; otherwise return nil.")
          UPDATE_SYNTAX_TABLE_FORWARD (from);
          c = FETCH_CHAR (from_byte);
          code = SYNTAX (c);
+         comstart_first = SYNTAX_COMSTART_FIRST (c);
          INC_BOTH (from, from_byte);
+         UPDATE_SYNTAX_TABLE_FORWARD (from);
          comstyle = 0;
-         if (from < stop && SYNTAX_COMSTART_FIRST (c)
+         if (from < stop && comstart_first
              && (c1 = FETCH_CHAR (from_byte),
                  SYNTAX_COMSTART_SECOND (c1)))
            {
@@ -1649,9 +1687,10 @@ between them, return t; otherwise return nil.")
               section.  */
            break;
          if (from < stop && SYNTAX_COMEND_FIRST (c)
+             && SYNTAX_COMMENT_STYLE (c) == comstyle
              && (c1 = FETCH_CHAR (from_byte),
-                 SYNTAX_COMEND_SECOND (c1))
-             && SYNTAX_COMMENT_STYLE (c) == comstyle)
+                 UPDATE_SYNTAX_TABLE_FORWARD (from),
+                 SYNTAX_COMEND_SECOND (c1)))
            /* we have encountered a comment end of the same style
               as the comment sequence which began this comment
               section */
@@ -1668,7 +1707,8 @@ between them, return t; otherwise return nil.")
     {
       while (1)
        {
-         int quoted;
+         int quoted, comstart_second;
+
          if (from <= stop)
            {
              SET_PT_BOTH (BEGV, BEGV_BYTE);
@@ -1677,34 +1717,34 @@ between them, return t; otherwise return nil.")
            }
 
          DEC_BOTH (from, from_byte);
+         /* char_quoted does UPDATE_SYNTAX_TABLE_BACKWARD (from).  */
          quoted = char_quoted (from, from_byte);
          if (quoted)
            {
              DEC_BOTH (from, from_byte);
              goto leave;
            }
-         UPDATE_SYNTAX_TABLE_BACKWARD (from);
          c = FETCH_CHAR (from_byte);
          code = SYNTAX (c);
          comstyle = 0;
          if (code == Sendcomment)
            comstyle = SYNTAX_COMMENT_STYLE (c);
-         temp_pos = dec_bytepos (from_byte);
+         comstart_second = SYNTAX_COMSTART_SECOND (c);
          if (from > stop && SYNTAX_COMEND_SECOND (c)
-             && (c1 = FETCH_CHAR (temp_pos),
-                 SYNTAX_COMEND_FIRST (c1))
+             && prev_char_comend_first (from, from_byte)
              && !char_quoted (from - 1, temp_pos))
            {
              /* We must record the comment style encountered so that
                 later, we can match only the proper comment begin
                 sequence of the same style.  */
-             code = Sendcomment;
-             comstyle = SYNTAX_COMMENT_STYLE (c1);
              DEC_BOTH (from, from_byte);
+             code = Sendcomment;
+             /* Calling char_quoted, above, set up global syntax position
+                at the new value of FROM.  */
+             comstyle = SYNTAX_COMMENT_STYLE (FETCH_CHAR (from_byte));
            }
-         if (from > stop && SYNTAX_COMSTART_SECOND (c)
-             && (c1 = FETCH_CHAR (temp_pos),
-                 SYNTAX_COMSTART_FIRST (c1))
+         if (from > stop && comstart_second
+             && prev_char_comstart_first (from, from_byte)
              && !char_quoted (from - 1, temp_pos))
            {
              /* We must record the comment style encountered so that
@@ -1798,14 +1838,17 @@ scan_lists (from, count, depth, sexpflag)
     {
       while (from < stop)
        {
+         int comstart_first, prefix;
          UPDATE_SYNTAX_TABLE_FORWARD (from);
          c = FETCH_CHAR (from_byte);
          code = SYNTAX (c);
+         comstart_first = SYNTAX_COMSTART_FIRST (c);
+         prefix = SYNTAX_PREFIX (c);
          if (depth == min_depth)
            last_good = from;
          INC_BOTH (from, from_byte);
          UPDATE_SYNTAX_TABLE_FORWARD (from);
-         if (from < stop && SYNTAX_COMSTART_FIRST (c)
+         if (from < stop && comstart_first
              && SYNTAX_COMSTART_SECOND (FETCH_CHAR (from_byte))
              && parse_sexp_ignore_comments)
            {
@@ -1817,10 +1860,10 @@ scan_lists (from, count, depth, sexpflag)
              code = Scomment;
              comstyle = SYNTAX_COMMENT_STYLE (FETCH_CHAR (from_byte));
              INC_BOTH (from, from_byte);
+             UPDATE_SYNTAX_TABLE_FORWARD (from);
            }
          
-         UPDATE_SYNTAX_TABLE_FORWARD (from);
-         if (SYNTAX_PREFIX (c))
+         if (prefix)
            continue;
 
          switch (SWITCH_ENUM_CAST (code))
@@ -1871,6 +1914,7 @@ scan_lists (from, count, depth, sexpflag)
                    }
                  UPDATE_SYNTAX_TABLE_FORWARD (from);
                  c = FETCH_CHAR (from_byte);
+                 INC_BOTH (from, from_byte);
                  if (code == Scomment 
                      ? (SYNTAX (c) == Sendcomment
                         && SYNTAX_COMMENT_STYLE (c) == comstyle)
@@ -1879,10 +1923,10 @@ scan_lists (from, count, depth, sexpflag)
                       as the comment sequence which began this comment
                       section */
                    break;
-                 INC_BOTH (from, from_byte);
                  if (from < stop && SYNTAX_COMEND_FIRST (c)
-                     && SYNTAX_COMEND_SECOND (FETCH_CHAR (from_byte))
                      && SYNTAX_COMMENT_STYLE (c) == comstyle
+                     && (UPDATE_SYNTAX_TABLE_FORWARD (from),
+                         SYNTAX_COMEND_SECOND (FETCH_CHAR (from_byte)))
                      && code == Scomment)
                    /* we have encountered a comment end of the same style
                       as the comment sequence which began this comment
@@ -1975,25 +2019,22 @@ scan_lists (from, count, depth, sexpflag)
          comstyle = 0;
          if (code == Sendcomment)
            comstyle = SYNTAX_COMMENT_STYLE (c);
-         temp_pos = from_byte;
-         if (! NILP (current_buffer->enable_multibyte_characters))
-           DEC_POS (temp_pos);
-         else
-           temp_pos--;
          if (from > stop && SYNTAX_COMEND_SECOND (c)
-             && (c1 = FETCH_CHAR (temp_pos), SYNTAX_COMEND_FIRST (c1))
+             && prev_char_comstart_first (from, from_byte)
              && parse_sexp_ignore_comments)
            {
-             /* we must record the comment style encountered so that
+             /* We must record the comment style encountered so that
                 later, we can match only the proper comment begin
-                sequence of the same style */
-             code = Sendcomment;
-             comstyle = SYNTAX_COMMENT_STYLE (c1);
+                sequence of the same style.  */
              DEC_BOTH (from, from_byte);
+             UPDATE_SYNTAX_TABLE_BACKWARD (from);
+             code = Sendcomment;
+             comstyle = SYNTAX_COMMENT_STYLE (FETCH_CHAR (from_byte));
            }
          
          /* Quoting turns anything except a comment-ender
-            into a word character.  */
+            into a word character.  Note that this if cannot be true
+            if we decremented FROM in the if-statement above.  */
          if (code != Sendcomment && char_quoted (from, from_byte))
            code = Sword;
          else if (SYNTAX_PREFIX (c))
@@ -2192,11 +2233,15 @@ This includes chars with \"quote\" or \"prefix\" syntax (' or p).")
   int pos_byte = PT_BYTE;
   int c;
 
-  if (pos > beg) 
+  if (pos <= beg) 
     {
-      SETUP_SYNTAX_TABLE (pos, -1);
+      SET_PT_BOTH (opoint, opoint_byte);
+
+      return Qnil;
     }
 
+  SETUP_SYNTAX_TABLE (pos, -1);
+
   DEC_BOTH (pos, pos_byte);
 
   while (!char_quoted (pos, pos_byte)