No-op optimization in substring.

* lib.c (sub_str): Optimization: if the range spans
the entire string, just return it; don't allocate
a copy.

1 files changed, 2 insertions, 0 deletions

diff --git a/lib.c b/lib.c
index 14b4348d..ec8735e1 100644
--- a/lib.c
+++ b/lib.c
@@ -3742,6 +3742,8 @@ val sub_str(val str_in, val from, val to)
 
   if (ge(from, to)) {
     return null_string;
+  } else if (from == zero && eql(to, len)) {
+    return str_in;
   } else {
     size_t nchar = c_num(to) - c_num(from) + 1;
     wchar_t *sub = chk_wmalloc(nchar);