type_traits: Add common_type.

2008-07-08  Chris Fairles  <chris.fairles@gmail.com>

        * include/std/type_traits: Add common_type.
        * testsuite/20_util/common_type/requirements/
	explicit_instantiation.cc: New.
        * testsuite/20_util/common_type/requirements/
	typedefs-1.cc: Likewise.

From-SVN: r137618

libstdc++-v3/ChangeLog

+2008-07-08  Chris Fairles  <chris.fairles@gmail.com>
+
+        * include/std/type_traits: Add common_type.
+        * testsuite/20_util/common_type/requirements/
+	explicit_instantiation.cc: New.
+        * testsuite/20_util/common_type/requirements/
+	typedefs-1.cc: Likewise.
+
 2008-07-07  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* testsuite/lib/libstdc++.exp (check_v3_target_stdint): New.

libstdc++-v3/include/std/type_traits

@@ -551,6 +551,41 @@ namespace std
   // Integral, but don't define.
   template<>
     struct make_signed<bool>;
+
+  template<typename... _Tp>
+    struct common_type;
+
+  template<typename _Tp>
+    struct common_type<_Tp>
+    {
+      static_assert(sizeof(_Tp) > 0, "must be complete type");
+      typedef _Tp type;
+    };
+
+  template<typename _Tp, typename _Up>
+    class common_type<_Tp, _Up>
+    {
+      static_assert(sizeof(_Tp) > 0, "must be complete type");
+      static_assert(sizeof(_Up) > 0, "must be complete type");
+
+      static _Tp&& __t();
+      static _Up&& __u();
+
+      // HACK: Prevents optimization of ?: in the decltype
+      // expression when the condition is the literal, "true".
+      // See, PR36628.
+      static bool __true_or_false();
+
+    public:
+      typedef decltype(__true_or_false() ? __t() : __u()) type;
+    };
+
+  template<typename _Tp, typename _Up, typename... _Vp>
+    struct common_type<_Tp, _Up, _Vp...>
+    {
+      typedef typename
+        common_type<typename common_type<_Tp, _Up>::type, _Vp...>::type type;
+    };
 }
 
 #endif  // __GXX_EXPERIMENTAL_CXX0X__

libstdc++-v3/testsuite/20_util/common_type/requirements/explicit_instantiation.cc

+// { dg-options "-std=gnu++0x" }
+// { dg-do compile }
+
+// Copyright (C) 2008 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+// As a special exception, you may use this file as part of a free software
+// library without restriction.  Specifically, if other files instantiate
+// templates or use macros or inline functions from this file, or you compile
+// this file and link it with other files to produce an executable, this
+// file does not by itself cause the resulting executable to be covered by
+// the GNU General Public License.  This exception does not however
+// invalidate any other reasons why the executable file might be covered by
+// the GNU General Public License.
+
+// NB: This file is for testing type_traits with NO OTHER INCLUDES.
+
+#include <type_traits>
+
+namespace std
+{
+  typedef int test_type1;
+  typedef int& test_type2;
+  typedef double test_type3;
+  typedef float test_type4;
+  
+  template struct common_type<test_type1>;
+  template struct common_type<test_type1, test_type2>;
+  template struct common_type<test_type1, test_type2, test_type3>;
+  template struct common_type<test_type1, test_type2, test_type3, test_type4>;
+}

libstdc++-v3/testsuite/20_util/common_type/requirements/typedefs-1.cc

+// { dg-options "-std=gnu++0x" }
+//
+// Copyright (C) 2008 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING.  If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+#include <type_traits>
+#include <testsuite_hooks.h>
+
+#define JOIN( X, Y ) DO_JOIN( X, Y )
+#define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
+#define DO_JOIN2( X, Y ) X##Y
+
+#define COMMON_TYPE_TEST_1(type1, uid) \
+  typedef common_type<type1>::type JOIN(test_t,uid); \
+  VERIFY( (is_same<JOIN(test_t,uid), JOIN(test_t,uid)>::value) ); \
+  typedef common_type<const type1>::type JOIN(test_t,JOIN(uid,c)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,c)), \
+                   JOIN(test_t,JOIN(uid,c))>::value) ); \
+  typedef common_type<volatile type1>::type JOIN(test_t,JOIN(uid,v)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,v)), \
+                   JOIN(test_t,JOIN(uid,v))>::value) ); \
+  typedef common_type<const volatile type1>::type JOIN(test_t,JOIN(uid,cv)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,cv)), \
+                   JOIN(test_t,JOIN(uid,cv))>::value) ); \
+  typedef common_type<type1 &>::type JOIN(test_t,JOIN(uid,l)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,l)), \
+                   JOIN(test_t,JOIN(uid,l))>::value) ); \
+  typedef common_type<const type1 &>::type JOIN(test_t,JOIN(uid,lc)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,lc)), \
+                   JOIN(test_t,JOIN(uid,lc))>::value) ); \
+  typedef common_type<volatile type1 &>::type JOIN(test_t,JOIN(uid,lv)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,lv)), \
+                   JOIN(test_t,JOIN(uid,lv))>::value) ); \
+  typedef common_type<const volatile type1 &>::type JOIN(test_t,JOIN(uid,lcv)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,lcv)), \
+                   JOIN(test_t,JOIN(uid,lcv))>::value) ); \
+  typedef common_type<type1 &&>::type JOIN(test_t,JOIN(uid,r)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,r)), \
+                   JOIN(test_t,JOIN(uid,r))>::value) ); \
+  typedef common_type<const type1 &&>::type JOIN(test_t,JOIN(uid,rc)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,rc)), \
+                   JOIN(test_t,JOIN(uid,rc))>::value) ); \
+  typedef common_type<volatile type1 &&>::type JOIN(test_t,JOIN(uid,rv)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,rv)), \
+                   JOIN(test_t,JOIN(uid,rv))>::value) ); \
+  typedef common_type<const volatile type1 &&>::type JOIN(test_t,JOIN(uid,rcv)); \
+  VERIFY( (is_same<JOIN(test_t,JOIN(uid,rcv)), \
+                   JOIN(test_t,JOIN(uid,rcv))>::value) )
+    
+struct A { };
+struct B : A { };
+
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+  using std::common_type;
+  using std::is_same;
+
+  // Positive tests.
+  COMMON_TYPE_TEST_1(int, 1);
+  COMMON_TYPE_TEST_1(double, 2);
+  COMMON_TYPE_TEST_1(A, 3);
+  COMMON_TYPE_TEST_1(B, 4);
+}
+
+#define COMMON_TYPE_TEST_2_IMPL(type1, type2, type3, uid) \
+  typedef common_type<type1, type2>::type  	JOIN(JOIN(test, uid),_t1); \
+  typedef common_type<type2, type1>::type  	JOIN(JOIN(test, uid),_t2); \
+  VERIFY( (is_same<JOIN(JOIN(test, uid),_t1), type3>::value) ); \
+  VERIFY( (is_same<JOIN(JOIN(test, uid),_t2), type3>::value) )
+
+#define NO_CV
+  
+#define COMMON_TYPE_TEST_2(cv_qual, type1, type2, type3, uid) \
+  COMMON_TYPE_TEST_2_IMPL(cv_qual type1, type2, type3, uid); \
+  COMMON_TYPE_TEST_2_IMPL(cv_qual type1 &, type2, type3, JOIN(uid,l)); \
+  COMMON_TYPE_TEST_2_IMPL(cv_qual type1 &&, type2, type3, JOIN(uid,r))
+
+#define COMMON_TYPE_TEST_ALL_2(type1, type2, type3, uid) \
+  COMMON_TYPE_TEST_2(NO_CV, type1, type2, type3, uid); \
+  COMMON_TYPE_TEST_2(const, type1, type2, type3, uid); \
+  COMMON_TYPE_TEST_2(volatile, type1, type2, type3, uid); \
+  COMMON_TYPE_TEST_2(const volatile, type1, type2, type3, uid)
+
+void test02()
+{
+  bool test __attribute__((unused)) = true;
+  using std::common_type;
+  using std::is_same;
+  
+  COMMON_TYPE_TEST_ALL_2(int, int, int, 1);
+  COMMON_TYPE_TEST_ALL_2(int, double, double, 2);
+  COMMON_TYPE_TEST_2(NO_CV, A, A, A, 3);
+  COMMON_TYPE_TEST_2(const, A, A, const A, 4);
+  COMMON_TYPE_TEST_2(NO_CV, B, A, A, 5);  
+}
+
+int main()
+{
+  test01();
+  test02();
+  return 0;
+}