Fix PR#25973 : 'basic_string::assign(InputIt, InputIt) doesn't provide the strong exception safety guarantee'. This turned out to be a pervasive problem in <string>, which required a fair amount of rework. Add in an optimization for when iterators provide noexcept increment/comparison/assignment/dereference (which covers many of the iterators in libc++). Reviewed as http://reviews.llvm.org/D15862

llvm-svn: 257682

1 files changed, 23 insertions, 0 deletions

diff --git a/libcxx/include/iterator b/libcxx/include/iterator
index 8dd6bd59c1a..8d9b31101bd 100644
--- a/libcxx/include/iterator
+++ b/libcxx/include/iterator
@@ -437,6 +437,12 @@ struct __is_bidirectional_iterator : public __has_iterator_category_convertible_
 template <class _Tp>
 struct __is_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {};
 
+template <class _Tp>
+struct __is_exactly_input_iterator
+    : public integral_constant<bool, 
+    	 __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value && 
+    	!__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};
+
 template<class _Category, class _Tp, class _Distance = ptrdiff_t,
          class _Pointer = _Tp*, class _Reference = _Tp&>
 struct _LIBCPP_TYPE_VIS_ONLY iterator
@@ -1404,6 +1410,23 @@ operator+(typename __wrap_iter<_Iter>::difference_type __n,
     return __x;
 }
 
+template <class _Iter>
+struct __libcpp_is_trivial_iterator
+	: public _LIBCPP_BOOL_CONSTANT(is_pointer<_Iter>::value) {};
+	
+template <class _Iter>
+struct __libcpp_is_trivial_iterator<move_iterator<_Iter> >
+	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+
+template <class _Iter>
+struct __libcpp_is_trivial_iterator<reverse_iterator<_Iter> >
+	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+
+template <class _Iter>
+struct __libcpp_is_trivial_iterator<__wrap_iter<_Iter> >
+	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+
+
 template <class _Tp, size_t _Np>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _Tp*