utf8.c: Prevent reading before buffer start

Make sure there is something before the character being read before
reading it.

diff --git a/utf8.c b/utf8.c
index e4b927d..c8c6e55 100644 (file)
--- a/utf8.c
+++ b/utf8.c
@@ -3495,7 +3495,9 @@ Perl__swash_to_invlist(pTHX_ SV* const swash)
 
     /* If the ending is somehow corrupt and isn't a new line, add another
      * element for the final range that isn't in the inversion list */
-    if (! (*lend == '\n' || (*lend == '\0' && *(lend - 1) == '\n'))) {
+    if (! (*lend == '\n'
+       || (*lend == '\0' && (lcur == 0 || *(lend - 1) == '\n'))))
+    {
        elements++;
     }