(string_char_to_byte): Handle invalid multibyte sequence

correctly.
(string_byte_to_char): Likesize.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/fns.c b/src/fns.c
index 6e7723ccaa0..e406ce3ecfd 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -845,7 +845,7 @@ string_char_to_byte (string, char_index)
           while (best_above_byte > 0
                  && !CHAR_HEAD_P (XSTRING (string)->data[best_above_byte]))
             best_above_byte--;
-          if (XSTRING (string)->data[best_above_byte] < 0x80)
+          if (!BASE_LEADING_CODE_P (XSTRING (string)->data[best_above_byte]))
             best_above_byte = best_above_byte_saved;
           best_above--;
         }
@@ -911,7 +911,7 @@ string_byte_to_char (string, byte_index)
           while (best_above_byte > 0
                  && !CHAR_HEAD_P (XSTRING (string)->data[best_above_byte]))
             best_above_byte--;
-          if (XSTRING (string)->data[best_above_byte] < 0x80)
+          if (!BASE_LEADING_CODE_P (XSTRING (string)->data[best_above_byte]))
             best_above_byte = best_above_byte_saved;
           best_above--;
         }