[pair] Mark constructors as conditionally noexcept

Summary:
std::tuple marks its constructors as noexcept when the corresponding
memberwise constructors are noexcept too -- this commit improves std::pair
so that it behaves the same.

This is a re-application of r348824, which broke the build in C++03 mode
because a test was marked as supported in C++03 when it shouldn't be.

Note:
I did not add support in the explicit and non-explicit `pair(_Tuple&& __p)`
constructors because those are non-standard extensions, and supporting them
properly is tedious (we have to copy the rvalue-referenceness of the deduced
_Tuple&& onto the result of tuple_element).

<rdar://problem/29537079>

Reviewers: mclow.lists, EricWF

Subscribers: christof, llvm-commits

Differential Revision: https://reviews.llvm.org/D48669

llvm-svn: 348847

libcxx/include/utility

@@ -409,62 +409,80 @@ struct _LIBCPP_TEMPLATE_VIS pair
             _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-    pair() : first(), second() {}
+    pair() _NOEXCEPT_(is_nothrow_default_constructible<first_type>::value &&
+                      is_nothrow_default_constructible<second_type>::value)
+        : first(), second() {}
 
     template <bool _Dummy = true, _EnableB<
              _CheckArgsDep<_Dummy>::template __enable_explicit<_T1 const&, _T2 const&>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(_T1 const& __t1, _T2 const& __t2)
+        _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
+                   is_nothrow_copy_constructible<second_type>::value)
         : first(__t1), second(__t2) {}
 
     template<bool _Dummy = true, _EnableB<
             _CheckArgsDep<_Dummy>::template __enable_implicit<_T1 const&, _T2 const&>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(_T1 const& __t1, _T2 const& __t2)
+        _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
+                   is_nothrow_copy_constructible<second_type>::value)
         : first(__t1), second(__t2) {}
 
     template<class _U1, class _U2, _EnableB<
              _CheckArgs::template __enable_explicit<_U1, _U2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(_U1&& __u1, _U2&& __u2)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
+                    is_nothrow_constructible<second_type, _U2>::value))
         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
 
     template<class _U1, class _U2, _EnableB<
             _CheckArgs::template __enable_implicit<_U1, _U2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(_U1&& __u1, _U2&& __u2)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
+                    is_nothrow_constructible<second_type, _U2>::value))
         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
 
     template<class _U1, class _U2, _EnableB<
             _CheckArgs::template __enable_explicit<_U1 const&, _U2 const&>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(pair<_U1, _U2> const& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
+                    is_nothrow_constructible<second_type, _U2 const&>::value))
         : first(__p.first), second(__p.second) {}
 
     template<class _U1, class _U2, _EnableB<
             _CheckArgs::template __enable_implicit<_U1 const&, _U2 const&>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(pair<_U1, _U2> const& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
+                    is_nothrow_constructible<second_type, _U2 const&>::value))
         : first(__p.first), second(__p.second) {}
 
     template<class _U1, class _U2, _EnableB<
             _CheckArgs::template __enable_explicit<_U1, _U2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(pair<_U1, _U2>&&__p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
+                    is_nothrow_constructible<second_type, _U2&&>::value))
         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
 
     template<class _U1, class _U2, _EnableB<
             _CheckArgs::template __enable_implicit<_U1, _U2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(pair<_U1, _U2>&& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
+                    is_nothrow_constructible<second_type, _U2&&>::value))
         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
 
     template<class _Tuple, _EnableB<
@@ -487,6 +505,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     _LIBCPP_INLINE_VISIBILITY
     pair(piecewise_construct_t __pc,
          tuple<_Args1...> __first_args, tuple<_Args2...> __second_args)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _Args1...>::value &&
+                    is_nothrow_constructible<second_type, _Args2...>::value))
         : pair(__pc, __first_args, __second_args,
                 typename __make_tuple_indices<sizeof...(_Args1)>::type(),
                 typename __make_tuple_indices<sizeof...(_Args2) >::type()) {}

libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/U_V.pass.cpp

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template<class U, class V> pair(U&& x, V&& y);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>, int, int>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>, int, int>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>, int, int>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>, int, int>::value, "");
+    }
+}

libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_first_const_second.pass.cpp

@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// pair(const T1& x, const T2& y);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    constexpr explicit ExplicitT(ExplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    constexpr ImplicitT(ImplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(ExplicitNothrowT const&) noexcept {}
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(ImplicitNothrowT const&) noexcept {}
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
+                                                     ExplicitT const&, ExplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>,
+                                                     ExplicitNothrowT const&, ExplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>,
+                                                     ExplicitT const&, ExplicitNothrowT const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>,
+                                                     ExplicitNothrowT const&, ExplicitNothrowT const&>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>,
+                                                     ImplicitT const&, ImplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>,
+                                                     ImplicitNothrowT const&, ImplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>,
+                                                     ImplicitT const&, ImplicitNothrowT const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
+                                                     ImplicitNothrowT const&, ImplicitNothrowT const&>::value, "");
+    }
+}

libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_pair_U_V.pass.cpp

@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template <class U, class V> EXPLICIT constexpr pair(const pair<U, V>& p);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    constexpr explicit ExplicitT(ExplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    constexpr ImplicitT(ImplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+    }
+}

libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/default.pass.cpp

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// constexpr pair();
+
+#include <utility>
+#include <type_traits>
+
+#include "archetypes.hpp"
+
+
+int main() {
+    using NonThrowingDefault = NonThrowingTypes::DefaultOnly;
+    using ThrowingDefault = NonTrivialTypes::DefaultOnly;
+    static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, ThrowingDefault>>::value, "");
+    static_assert(!std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, ThrowingDefault>>::value, "");
+    static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, NonThrowingDefault>>::value, "");
+    static_assert( std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, NonThrowingDefault>>::value, "");
+}

libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/piecewise.pass.cpp

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template <class... Args1, class... Args2>
+//     pair(piecewise_construct_t, tuple<Args1...> first_args,
+//                                 tuple<Args2...> second_args);
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "archetypes.hpp"
+
+
+int main() {
+    using NonThrowingConvert = NonThrowingTypes::ConvertingType;
+    using ThrowingConvert = NonTrivialTypes::ConvertingType;
+    static_assert(!std::is_nothrow_constructible<std::pair<ThrowingConvert, ThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert(!std::is_nothrow_constructible<std::pair<NonThrowingConvert, ThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert(!std::is_nothrow_constructible<std::pair<ThrowingConvert, NonThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert( std::is_nothrow_constructible<std::pair<NonThrowingConvert, NonThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+}