Implement <variant>

	* include/Makefile.am: Add new file std/variant.
	* include/Makefile.in: Generated from Makefile.am.
	* include/bits/enable_special_members.h: Add a tag type to allow
	the construction in non-default constructor.
	* include/bits/uses_allocator.h: Add convenience traits to
	detect constructibility.
	* include/std/variant: Implement <variant>.
	* testsuite/20_util/variant/compile.cc: Compile-time tests.
	* testsuite/20_util/variant/run.cc: Runtime tests.

From-SVN: r239590

libstdc++-v3/ChangeLog

+2016-08-18  Tim Shen  <timshen@google.com>
+
+	Implement <variant>
+
+	* include/Makefile.am: Add new file std/variant.
+	* include/Makefile.in: Generated from Makefile.am.
+	* include/bits/enable_special_members.h: Add a tag type to allow
+	the construction in non-default constructor.
+	* include/bits/uses_allocator.h: Add convenience traits to
+	detect constructibility.
+	* include/std/variant: Implement <variant>.
+	* testsuite/20_util/variant/compile.cc: Compile-time tests.
+	* testsuite/20_util/variant/run.cc: Runtime tests.
+
 2016-08-18  Jonathan Wakely  <jwakely@redhat.com>
 
 	* doc/xml/manual/test.xml (test.run.permutations): Expand section.

libstdc++-v3/include/Makefile.am

@@ -77,6 +77,7 @@ std_headers = \
 	${std_srcdir}/unordered_set \
 	${std_srcdir}/utility \
 	${std_srcdir}/valarray \
+	${std_srcdir}/variant \
 	${std_srcdir}/vector
 
 bits_srcdir = ${glibcxx_srcdir}/include/bits

libstdc++-v3/include/Makefile.in

@@ -367,6 +367,7 @@ std_headers = \
 	${std_srcdir}/unordered_set \
 	${std_srcdir}/utility \
 	${std_srcdir}/valarray \
+	${std_srcdir}/variant \
 	${std_srcdir}/vector
 
 bits_srcdir = ${glibcxx_srcdir}/include/bits

libstdc++-v3/include/bits/enable_special_members.h

@@ -36,13 +36,33 @@ namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
+  struct _Enable_default_constructor_tag
+  {
+    explicit _Enable_default_constructor_tag() = default;
+  };
+
 /**
   * @brief A mixin helper to conditionally enable or disable the default
   * constructor.
   * @sa _Enable_special_members
   */
 template<bool _Switch, typename _Tag = void>
-  struct _Enable_default_constructor { };
+  struct _Enable_default_constructor
+  {
+    constexpr _Enable_default_constructor() noexcept = default;
+    constexpr _Enable_default_constructor(_Enable_default_constructor const&)
+      noexcept  = default;
+    constexpr _Enable_default_constructor(_Enable_default_constructor&&)
+      noexcept = default;
+    _Enable_default_constructor&
+    operator=(_Enable_default_constructor const&) noexcept = default;
+    _Enable_default_constructor&
+    operator=(_Enable_default_constructor&&) noexcept = default;
+
+    // Can be used in other ctors.
+    constexpr explicit
+    _Enable_default_constructor(_Enable_default_constructor_tag) { }
+  };
 
 
 /**
@@ -86,7 +106,20 @@ template<bool _Default, bool _Destructor,
 
 template<typename _Tag>
   struct _Enable_default_constructor<false, _Tag>
-  { constexpr _Enable_default_constructor() noexcept = delete; };
+  {
+    constexpr _Enable_default_constructor() noexcept = delete;
+    constexpr _Enable_default_constructor(_Enable_default_constructor const&)
+      noexcept  = default;
+    constexpr _Enable_default_constructor(_Enable_default_constructor&&)
+      noexcept = default;
+    _Enable_default_constructor&
+    operator=(_Enable_default_constructor const&) noexcept = default;
+    _Enable_default_constructor&
+    operator=(_Enable_default_constructor&&) noexcept = default;
+
+    // Can be used in other ctors.
+    explicit _Enable_default_constructor(_Enable_default_constructor_tag) { }
+  };
 
 template<typename _Tag>
   struct _Enable_destructor<false, _Tag>

libstdc++-v3/include/bits/uses_allocator.h

@@ -113,6 +113,57 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     constexpr bool uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
 #endif // C++17
 
+  template<template<typename...> class _Predicate,
+	   typename _Tp, typename _Alloc, typename... _Args>
+    struct __is_uses_allocator_predicate
+    : conditional<uses_allocator<_Tp, _Alloc>::value,
+      __or_<_Predicate<_Tp, allocator_arg_t, _Alloc, _Args...>,
+	    _Predicate<_Tp, _Args..., _Alloc>>,
+      _Predicate<_Tp, _Args...>>::type { };
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    struct __is_uses_allocator_constructible
+    : __is_uses_allocator_predicate<is_constructible, _Tp, _Alloc, _Args...>
+    { };
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    constexpr bool __is_uses_allocator_constructible_v =
+      __is_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    struct __is_nothrow_uses_allocator_constructible
+    : __is_uses_allocator_predicate<is_nothrow_constructible,
+				    _Tp, _Alloc, _Args...>
+    { };
+
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    constexpr bool __is_nothrow_uses_allocator_constructible_v =
+      __is_nothrow_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
+
+  template<typename _Tp, typename... _Args>
+    void __uses_allocator_construct_impl(__uses_alloc0 __a, _Tp* __ptr,
+					 _Args&&... __args)
+    { new (__ptr) _Tp(forward<_Args>(__args)...); }
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    void __uses_allocator_construct_impl(__uses_alloc1<_Alloc> __a, _Tp* __ptr,
+					 _Args&&... __args)
+    { new (__ptr) _Tp(allocator_arg, *__a._M_a, forward<_Args>(__args)...); }
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    void __uses_allocator_construct_impl(__uses_alloc2<_Alloc> __a, _Tp* __ptr,
+					 _Args&&... __args)
+    { new (__ptr) _Tp(forward<_Args>(__args)..., *__a._M_a); }
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    void __uses_allocator_construct(const _Alloc& __a, _Tp* __ptr,
+				    _Args&&... __args)
+    {
+      __uses_allocator_construct_impl(__use_alloc<_Tp, _Alloc, _Args...>(__a),
+				      __ptr, forward<_Args>(__args)...);
+    }
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std