Improve reverse_iterate implementation

If the passed range is an rvalue, then move it into our private copy.
Otherwise, with nested ranges, there is no guarantee the thing will
still be alive once we get to iterating over it.

1 files changed, 6 insertions, 9 deletions

diff --git a/butl/utility b/butl/utility
index b1fa8f6..6efa4d0 100644
--- a/butl/utility
+++ b/butl/utility
@@ -5,6 +5,7 @@
 #ifndef BUTL_UTILITY
 #define BUTL_UTILITY
 
+#include <utility> // forward()
 #include <cstring> // strcmp
 
 namespace butl
@@ -32,22 +33,18 @@ namespace butl
   template <typename T>
   class reverse_range
   {
-    T& x_;
+    T x_;
 
   public:
-    reverse_range (T& x): x_ (x) {}
+    reverse_range (T&& x): x_ (std::forward<T> (x)) {}
 
-    auto begin () -> decltype (this->x_.rbegin ()) {return x_.rbegin ();}
-    auto end () -> decltype (this->x_.rend ()) {return x_.rend ();}
+    auto begin () const -> decltype (this->x_.rbegin ()) {return x_.rbegin ();}
+    auto end () const -> decltype (this->x_.rend ()) {return x_.rend ();}
   };
 
   template <typename T>
   inline reverse_range<T>
-  reverse_iterate (T& x) {return reverse_range<T> (x);}
-
-  template <typename T>
-  inline reverse_range<const T>
-  reverse_iterate (const T& x) {return reverse_range<const T> (x);}
+  reverse_iterate (T&& x) {return reverse_range<T> (std::forward<T> (x));}
 }
 
 #endif // BUTL_UTILITY