1 /* 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_VM_UTILITIES_TRAITS_IS_CLASS_DEFINED_HPP 26 #define SHARE_VM_UTILITIES_TRAITS_IS_CLASS_DEFINED_HPP 27 28 #include "utilities/traits/enableIf.hpp" 29 #include "utilities/traits/removeCv.hpp" 30 #include "utilities/traits/isClassOrUnion.hpp" 31 32 // Metafunction whose nested value member is true if T is defined 33 // (complete), and false if T is incomplete. 34 // If T is incomplete at the point where this 35 // metafunction is invoked, it must never be defined elsewhere in the 36 // program. 37 // Returns false if T is not a class type. 38 // Note: Currently can return true for a union, but this is subject to 39 // change and should not be relied upon. 40 template<typename T> 41 class IsClassDefined { 42 typedef char yes[1]; 43 typedef char no[2]; 44 45 template<typename U> 46 static typename EnableIf<sizeof(U) != 0, yes>::type& check(U*); 47 static no& check(...); 48 49 typedef typename RemoveCv<T>::type TNoCv; 50 51 public: 52 static const bool value = IsClassOrUnion<TNoCv>::value && 53 sizeof(check((T*)0)) == sizeof(yes); 54 }; 55 56 #endif // SHARE_VM_UTILITIES_TRAITS_IS_CLASS_DEFINED_HPP 57