LWG 3035. std::allocator's constructors should be constexpr

	LWG 3035. std::allocator's constructors should be constexpr
	* include/bits/allocator.h (allocator): Add constexpr to constructors
	for C++2a. Replace dynamic exception specifications with NOTHROW
	macro.
	(allocator, operator==, operator!=): Replace USE_NOEXCEPT macro with
	NOTHROW.
	* include/bits/c++config (_GLIBCXX20_CONSTEXPR): Define.
	* include/ext/malloc_allocator.h (malloc_allocator): Add constexpr
	to constructors for C++2a.
	* include/ext/new_allocator.h (new_allocator): Likewise.

From-SVN: r261703

libstdc++-v3/ChangeLog

+2018-06-18  Jonathan Wakely  <jwakely@redhat.com>
+
+	LWG 3035. std::allocator's constructors should be constexpr
+	* include/bits/allocator.h (allocator): Add constexpr to constructors
+	for C++2a. Replace dynamic exception specifications with NOTHROW
+	macro.
+	(allocator, operator==, operator!=): Replace USE_NOEXCEPT macro with
+	NOTHROW.
+	* include/bits/c++config (_GLIBCXX20_CONSTEXPR): Define.
+	* include/ext/malloc_allocator.h (malloc_allocator): Add constexpr
+	to constructors for C++2a.
+	* include/ext/new_allocator.h (new_allocator): Likewise.
+
 2018-06-16  Jonathan Wakely  <jwakely@redhat.com>
 
 	LWG 3076 basic_string CTAD ambiguity

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

@@ -128,19 +128,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       typedef true_type is_always_equal;
 #endif
 
-      allocator() throw() { }
+      // _GLIBCXX_RESOLVE_LIB_DEFECTS
+      // 3035. std::allocator's constructors should be constexpr
+      _GLIBCXX20_CONSTEXPR
+      allocator() _GLIBCXX_NOTHROW { }
 
-      allocator(const allocator& __a) throw()
+      _GLIBCXX20_CONSTEXPR
+      allocator(const allocator& __a) _GLIBCXX_NOTHROW
       : __allocator_base<_Tp>(__a) { }
+
 #if __cplusplus >= 201103L
       // Avoid implicit deprecation.
       allocator& operator=(const allocator&) = default;
 #endif
 
       template<typename _Tp1>
-	allocator(const allocator<_Tp1>&) throw() { }
+	_GLIBCXX20_CONSTEXPR
+	allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
 
-      ~allocator() throw() { }
+      ~allocator() _GLIBCXX_NOTHROW { }
 
       // Inherit everything else.
     };
@@ -148,25 +154,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _T1, typename _T2>
     inline bool
     operator==(const allocator<_T1>&, const allocator<_T2>&)
-    _GLIBCXX_USE_NOEXCEPT
+    _GLIBCXX_NOTHROW
     { return true; }
 
   template<typename _Tp>
     inline bool
     operator==(const allocator<_Tp>&, const allocator<_Tp>&)
-    _GLIBCXX_USE_NOEXCEPT
+    _GLIBCXX_NOTHROW
     { return true; }
 
   template<typename _T1, typename _T2>
     inline bool
     operator!=(const allocator<_T1>&, const allocator<_T2>&)
-    _GLIBCXX_USE_NOEXCEPT
+    _GLIBCXX_NOTHROW
     { return false; }
 
   template<typename _Tp>
     inline bool
     operator!=(const allocator<_Tp>&, const allocator<_Tp>&)
-    _GLIBCXX_USE_NOEXCEPT
+    _GLIBCXX_NOTHROW
     { return false; }
 
   // Invalid allocator<cv T> partial specializations.

libstdc++-v3/include/bits/c++config

@@ -122,15 +122,23 @@
 #endif
 
 #ifndef _GLIBCXX17_CONSTEXPR
-# if __cplusplus > 201402L
+# if __cplusplus >= 201703L
 #  define _GLIBCXX17_CONSTEXPR constexpr
 # else
 #  define _GLIBCXX17_CONSTEXPR
 # endif
 #endif
 
+#ifndef _GLIBCXX20_CONSTEXPR
+# if __cplusplus > 201703L
+#  define _GLIBCXX20_CONSTEXPR constexpr
+# else
+#  define _GLIBCXX20_CONSTEXPR
+# endif
+#endif
+
 #ifndef _GLIBCXX17_INLINE
-# if __cplusplus > 201402L
+# if __cplusplus >= 201703L
 #  define _GLIBCXX17_INLINE inline
 # else
 #  define _GLIBCXX17_INLINE

libstdc++-v3/include/ext/malloc_allocator.h

@@ -75,11 +75,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       typedef std::true_type propagate_on_container_move_assignment;
 #endif
 
+      _GLIBCXX20_CONSTEXPR
       malloc_allocator() _GLIBCXX_USE_NOEXCEPT { }
 
+      _GLIBCXX20_CONSTEXPR
       malloc_allocator(const malloc_allocator&) _GLIBCXX_USE_NOEXCEPT { }
 
       template<typename _Tp1>
+	_GLIBCXX20_CONSTEXPR
         malloc_allocator(const malloc_allocator<_Tp1>&)
 	_GLIBCXX_USE_NOEXCEPT { }
 

libstdc++-v3/include/ext/new_allocator.h

@@ -76,11 +76,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       typedef std::true_type propagate_on_container_move_assignment;
 #endif
 
+      _GLIBCXX20_CONSTEXPR
       new_allocator() _GLIBCXX_USE_NOEXCEPT { }
 
+      _GLIBCXX20_CONSTEXPR
       new_allocator(const new_allocator&) _GLIBCXX_USE_NOEXCEPT { }
 
       template<typename _Tp1>
+	_GLIBCXX20_CONSTEXPR
 	new_allocator(const new_allocator<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { }
 
       ~new_allocator() _GLIBCXX_USE_NOEXCEPT { }