[PATCH 1/2] c++: implement __is_function built-in trait

[PATCH 1/2] c++: implement __is_function built-in trait

[Ken Matsui]

This patch implements built-in trait for std::is_function.

gcc/cp/ChangeLog:

	* cp-trait.def: Define __is_function.
	* constraint.cc (diagnose_trait_expr): Handle CPTK_IS_FUNCTION.
	* semantics.cc (trait_expr_value): Likewise.
	(finish_trait_expr): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __is_function.
	* g++.dg/ext/is_function.C: New test.
---
 gcc/cp/constraint.cc                     |  3 ++
 gcc/cp/cp-trait.def                      |  1 +
 gcc/cp/semantics.cc                      |  4 ++
 gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 ++
 gcc/testsuite/g++.dg/ext/is_function.C   | 55 ++++++++++++++++++++++++
 5 files changed, 66 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/is_function.C

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 273d15ab097..313869152d0 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3747,6 +3747,9 @@ diagnose_trait_expr (tree expr, tree args)
     case CPTK_IS_UNION:
       inform (loc, "  %qT is not a union", t1);
       break;
+    case CPTK_IS_FUNCTION:
+      inform (loc, "  %qT is not a function", t1);
+      break;
     case CPTK_IS_AGGREGATE:
       inform (loc, "  %qT is not an aggregate", t1);
       break;
diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index bac593c0094..28aed4d39bb 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -82,6 +82,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_ASSIGNABLE, "__is_trivially_assignable", 2)
 DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1)
 DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1)
 DEFTRAIT_EXPR (IS_UNION, "__is_union", 1)
+DEFTRAIT_EXPR (IS_FUNCTION, "__is_function", 1)
 DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2)
 DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2)
 /* FIXME Added space to avoid direct usage in GCC 13.  */
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 87c2e8a7111..0b905d0c64b 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -11992,6 +11992,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
       return type_code1 == ENUMERAL_TYPE;
 
+    case CPTK_IS_FUNCTION:
+      return type_code1 == FUNCTION_TYPE;
+
     case CPTK_IS_FINAL:
       return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1);
 
@@ -12200,6 +12203,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2)
     case CPTK_IS_ENUM:
     case CPTK_IS_UNION:
     case CPTK_IS_SAME:
+    case CPTK_IS_FUNCTION:
       break;
 
     case CPTK_IS_LAYOUT_COMPATIBLE:
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index f343e153e56..452d2ccad4d 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -146,3 +146,6 @@
 #if !__has_builtin (__remove_cvref)
 # error "__has_builtin (__remove_cvref) failed"
 #endif
+#if !__has_builtin (__is_function)
+# error "__has_builtin (__is_function) failed"
+#endif
diff --git a/gcc/testsuite/g++.dg/ext/is_function.C b/gcc/testsuite/g++.dg/ext/is_function.C
new file mode 100644
index 00000000000..acd37800636
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/is_function.C
@@ -0,0 +1,55 @@
+// { dg-do compile { target c++11 } }
+
+#include <testsuite_tr1.h>
+
+using namespace __gnu_test;
+
+#define SA(X) static_assert((X),#X)
+
+struct A
+{ void fn(); };
+
+template<typename>
+struct AHolder { };
+
+template<class T, class U>
+struct AHolder<U T::*>
+{ using type = U; };
+
+// Positive tests.
+SA(__is_function(int (int)));
+SA(__is_function(ClassType (ClassType)));
+SA(__is_function(float (int, float, int[], int&)));
+SA(__is_function(int (int, ...)));
+SA(__is_function(bool (ClassType) const));
+SA(__is_function(AHolder<decltype(&A::fn)>::type));
+
+void fn();
+SA(__is_function(decltype(fn)));
+
+// Negative tests.
+SA(!__is_function(int));
+SA(!__is_function(int*));
+SA(!__is_function(int&));
+SA(!__is_function(void));
+SA(!__is_function(const void));
+SA(!__is_function(void*));
+SA(!__is_function(const void*));
+SA(!__is_function(void**));
+SA(!__is_function(std::nullptr_t));
+
+SA(!__is_function(AbstractClass));
+SA(!__is_function(int(&)(int)));
+SA(!__is_function(int(*)(int)));
+
+SA(!__is_function(A));
+SA(!__is_function(decltype(&A::fn)));
+
+struct FnCallOverload
+{ void operator()(); };
+SA(!__is_function(FnCallOverload));
+
+// Sanity check.
+SA(!__is_function(ClassType));
+SA(!__is_function(IncompleteClass));
+SA(!__is_function(IncompleteUnion));
-- 
2.40.0

[PATCH 2/2] libstdc++: use new built-in trait __is_function

[Ken Matsui]

This patch lets libstdc++ use new built-in trait __is_function.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_function): Use __is_function built-in trait.
---
 libstdc++-v3/include/std/type_traits | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 2bd607a8b8f..d008d5eb67d 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -594,6 +594,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
   /// is_function
+#if __has_builtin(__is_function)
+  template<typename _Tp>
+    struct is_function
+    : public __bool_constant<__is_function(_Tp)>
+    { };
+#else
   template<typename _Tp>
     struct is_function
     : public __bool_constant<!is_const<const _Tp>::value> { };
@@ -605,6 +611,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Tp>
     struct is_function<_Tp&&>
     : public false_type { };
+#endif
 
 #define __cpp_lib_is_null_pointer 201309L
 
-- 
2.40.0