#include <bits/move.h> // for std::move / std::forward, std::decay, and
// std::swap
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+#include <type_traits>
+#endif
+
_GLIBCXX_BEGIN_NAMESPACE(std)
+#ifdef __GXX_EXPERIMENTAL_CXX0X__
+// A trait that determines whether the initialization of a T from
+// arguments of type Args could possibly be the initialization of a
+// pointer from a null pointer constant.
+template<typename, typename...>
+struct __may_be_null_pointer_init
+ : public false_type { };
+
+template<typename _Tp, typename _Up>
+struct __may_be_null_pointer_init<_Tp*, _Up>
+ : public integral_constant<bool,
+ (is_integral<typename remove_reference<_Up>::type>::value
+ || is_enum<typename remove_reference<_Up>::type>::value)>
+ { };
+
+template<typename _Class, typename _Tp, typename _Up>
+struct __may_be_null_pointer_init<_Tp _Class::*, _Up>
+ : public integral_constant<bool,
+ (is_integral<typename remove_reference<_Up>::type>::value
+ || is_enum<typename remove_reference<_Up>::type>::value)>
+ { };
+#endif
+
/// pair holds two objects of arbitrary type.
template<class _T1, class _T2>
struct pair
: first(__a), second(__b) { }
#ifdef __GXX_EXPERIMENTAL_CXX0X__
- template<class _U1, class _U2>
- pair(_U1&& __x, _U2&& __y)
- : first(std::forward<_U1>(__x)),
- second(std::forward<_U2>(__y)) { }
+ // Omitted the following constructor, which appears in the C++0x
+ // working paper but is redundant with the variadic constructors
+ // below.
+ //
+ // template<class _U1, class _U2>
+ // pair(_U1&& __x, _U2&& __y);
pair(pair&& __p)
: first(std::move(__p.first)),
: first(std::move(__p.first)),
second(std::move(__p.second)) { }
- // http://gcc.gnu.org/ml/libstdc++/2007-08/msg00052.html
- template<class _U1, class _Arg0, class... _Args>
- pair(_U1&& __x, _Arg0&& __arg0, _Args&&... __args)
+ // This constructor is required so that lvalue pairs don't get
+ // pushed to the variadic constructor below.
+ template<class _U1, class _U2>
+ pair(pair<_U1, _U2>& __p)
+ : first(const_cast<const pair<_U1, _U2>&>(__p).first),
+ second(const_cast<const pair<_U1, _U2>&>(__p).second) { }
+
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 811. pair of pointers no longer works with literal 0
+
+ // Variadic constructor. The enable_if makes sure that we won't
+ // try to initialize a pointer from an integral type, which
+ // needs to be handled by a different constructor that will
+ // convert a null pointer constant to that pointer type. See
+ // library issue 767.
+ template<class _U1, class... _Args,
+ class _Checker
+ = typename enable_if<
+ (!__may_be_null_pointer_init<_T1, _U1>::value
+ && !__may_be_null_pointer_init<_T2, _Args...>::value),
+ void>::type>
+ pair(_U1&& __x, _Args&&... __args)
+ : first(std::forward<_U1>(__x)),
+ second(std::forward<_Args>(__args)...) { }
+
+ // Variadic constructor. The enable_if makes sure that the
+ // second argument isn't going to try to initialize a pointer
+ // from an integral type. However, T1 may be a pointer whose
+ // argument was a null pointer constant.
+ template<class... _Args,
+ class _Checker
+ = typename enable_if<
+ !__may_be_null_pointer_init<_T2, _Args...>::value,
+ void>::type>
+ pair(const _T1& __x, _Args&&... __args)
+ : first(__x),
+ second(std::forward<_Args>(__args)...) { }
+
+ // Constructor typically used when T2 is a pointer and the
+ // second argument was a null pointer constant. The enable_if
+ // makes sure that the first argument isn't going to try to
+ // initialize a pointer from an integral type.
+ template<class _U1,
+ class _Checker
+ = typename enable_if<
+ !__may_be_null_pointer_init<_T1, _U1>::value,
+ void>::type>
+ pair(_U1&& __x, const _T2& __y)
: first(std::forward<_U1>(__x)),
- second(std::forward<_Arg0>(__arg0),
- std::forward<_Args>(__args)...) { }
+ second(__y) { }
pair&
operator=(pair&& __p)
r.second.size() == 2 && p.second.size() == 0);
}
+struct X {
+ explicit X(int, int) { }
+
+private:
+ X(const X&) = delete;
+};
+
+struct move_only {
+ move_only() { }
+ move_only(move_only&&) { }
+
+private:
+ move_only(const move_only&) = delete;
+};
+
+void
+test3()
+{
+ int *ip = 0;
+ int X::*mp = 0;
+ std::pair<int*, int*> p1(0, 0);
+ std::pair<int*, int*> p2(ip, 0);
+ std::pair<int*, int*> p3(0, ip);
+ std::pair<int*, int*> p4(ip, ip);
+
+ std::pair<int X::*, int*> p5(0, 0);
+ std::pair<int X::*, int X::*> p6(mp, 0);
+ std::pair<int X::*, int X::*> p7(0, mp);
+ std::pair<int X::*, int X::*> p8(mp, mp);
+
+ std::pair<int*, X> p9(0, 1, 2);
+ std::pair<int X::*, X> p10(0, 1, 2);
+ std::pair<int*, X> p11(ip, 1, 2);
+ std::pair<int X::*, X> p12(mp, 1, 2);
+
+ std::pair<int*, move_only> p13(0);
+ std::pair<int X::*, move_only> p14(0);
+
+ std::pair<int*, move_only> p15(0, move_only());
+ std::pair<int X::*, move_only> p16(0, move_only());
+ std::pair<move_only, int*> p17(move_only(), 0);
+ std::pair<move_only, int X::*> p18(move_only(), 0);
+}
+
int
main()
{
test1();
test2();
+ test3();
}