std::uninitialized_copy tries to test assignability as follows:
is_assignable<_ValueType1, _RefType>::value
This is the wrong way around. For example, when the iterators are char*, this
ends up as
is_assignable<char, char&>::value
which is false. It should be
is_assignable<char&, char>::value
which is true.
The result is that uninitialized_copy needlessly picks the slow implementation.
Trivial fix attached. (No tests ran because I'm getting "runtest: command not
found" errors that I don't know how to fix.)
Index: libstdc++-v3/include/bits/stl_uninitialized.h
===================================================================
--- libstdc++-v3/include/bits/stl_uninitialized.h (revision 219070)
+++ libstdc++-v3/include/bits/stl_uninitialized.h (working copy)
@@ -105,29 +105,29 @@
template<typename _InputIterator, typename _ForwardIterator>
inline _ForwardIterator
uninitialized_copy(_InputIterator __first, _InputIterator __last,
_ForwardIterator __result)
{
typedef typename iterator_traits<_InputIterator>::value_type
_ValueType1;
typedef typename iterator_traits<_ForwardIterator>::value_type
_ValueType2;
#if __cplusplus < 201103L
const bool __assignable = true;
#else
// trivial types can have deleted assignment
typedef typename iterator_traits<_InputIterator>::reference _RefType;
- const bool __assignable = is_assignable<_ValueType1, _RefType>::value;
+ const bool __assignable = is_assignable<_RefType, _ValueType1>::value;
#endif
return std::__uninitialized_copy<__is_trivial(_ValueType1)
&& __is_trivial(_ValueType2)
&& __assignable>::
__uninit_copy(__first, __last, __result);
}
template<bool _TrivialValueType>
struct __uninitialized_fill
{
template<typename _ForwardIterator, typename _Tp>
static void
