(scan_lists): Simplify backward string scan.

Fix off-by-one boundary check for string and comment fences.

1 files changed, 5 insertions, 11 deletions

diff --git a/src/syntax.c b/src/syntax.c
index 30fc94267cd..72f7a5c5209 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -2398,8 +2398,8 @@ scan_lists (from, count, depth, sexpflag)
             case Sstring_fence:
               while (1)
                 {
-                  DEC_BOTH (from, from_byte);
                   if (from == stop) goto lose;
+                  DEC_BOTH (from, from_byte);
                   UPDATE_SYNTAX_TABLE_BACKWARD (from);
                   if (!char_quoted (from, from_byte)
                       && (c = FETCH_CHAR (from_byte),
@@ -2414,19 +2414,13 @@ scan_lists (from, count, depth, sexpflag)
               while (1)
                 {
                   if (from == stop) goto lose;
-                  temp_pos = from_byte;
-                  if (! NILP (current_buffer->enable_multibyte_characters))
-                    DEC_POS (temp_pos);
-                  else
-                    temp_pos--;
-                  UPDATE_SYNTAX_TABLE_BACKWARD (from - 1);
-                  if (!char_quoted (from - 1, temp_pos)
-                      && stringterm == (c = FETCH_CHAR (temp_pos))
+                  DEC_BOTH (from, from_byte);
+                  UPDATE_SYNTAX_TABLE_BACKWARD (from);
+                  if (!char_quoted (from, from_byte)
+                      && stringterm == (c = FETCH_CHAR (from_byte))
                       && SYNTAX_WITH_MULTIBYTE_CHECK (c) == Sstring)
                     break;
-                  DEC_BOTH (from, from_byte);
                 }
-              DEC_BOTH (from, from_byte);
               if (!depth && sexpflag) goto done2;
               break;
             default: