# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1481567512 -3600
# Node ID 887f9d80a1370ec3279ba29ed79ee17bb9d94340
# Parent  d11750cc8bf3ff8e16a4f8af467337be9aaf424c
Fixed the substring length calculation for negative step values.

diff -r d11750cc8bf3 -r 887f9d80a137 templates/native/str.c
--- a/templates/native/str.c	Mon Dec 12 18:43:29 2016 +0100
+++ b/templates/native/str.c	Mon Dec 12 19:31:52 2016 +0100
@@ -125,7 +125,7 @@
     int istep = __load_via_object(step->value, __pos___data__).intvalue;
 
     /* Calculate the size of the substring. */
-    size_t resultsize = ((iend - istart - 1) / istep) + 1;
+    size_t resultsize = ((iend - istart - (istep > 0 ? 1 : -1)) / istep) + 1;
     int to, from;
 
     /* Reserve space for a new string. */