[libcxx] r341975 - Fix PR# 38900 - don't call swap inside of random_shuffle when we'd be swapping an element with itself

[Marshall Clow via cfe-commits]

Author: marshall
Date: Tue Sep 11 11:33:45 2018
New Revision: 341975

URL: http://llvm.org/viewvc/llvm-project?rev=341975&view=rev
Log:
Fix PR# 38900 - don't call swap inside of random_shuffle when we'd be swapping an element with itself

Modified:
    libcxx/trunk/include/algorithm

Modified: libcxx/trunk/include/algorithm
URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/algorithm?rev=341975&r1=341974&r2=341975&view=diff
==============================================================================
--- libcxx/trunk/include/algorithm (original)
+++ libcxx/trunk/include/algorithm Tue Sep 11 11:33:45 2018
@@ -2987,7 +2987,8 @@ random_shuffle(_RandomAccessIterator __f
         for (--__last; __first < __last; ++__first, --__d)
         {
             difference_type __i = __rand(__d);
-            swap(*__first, *(__first + __i));
+            if (__i != difference_type(0))
+	            swap(*__first, *(__first + __i));
         }
     }
 }