[PATCH v2 1/4] c++: Implement __add_pointer built-in trait

[Ken Matsui <kmatsui@gcc.gnu.org>]

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

gcc/cp/ChangeLog:

	* cp-trait.def: Define __add_pointer.
	* semantics.cc (finish_trait_type): Handle CPTK_ADD_POINTER.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/has-builtin-1.C: Test existence of __add_pointer.
	* g++.dg/ext/add_pointer.C: New test.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 gcc/cp/cp-trait.def                      |  1 +
 gcc/cp/semantics.cc                      |  9 ++++++
 gcc/testsuite/g++.dg/ext/add_pointer.C   | 37 ++++++++++++++++++++++++
 gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 ++
 4 files changed, 50 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/ext/add_pointer.C

diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
index 394f006f20f..cec385ee501 100644
--- a/gcc/cp/cp-trait.def
+++ b/gcc/cp/cp-trait.def
@@ -48,6 +48,7 @@
 #define DEFTRAIT_TYPE_DEFAULTED
 #endif
 
+DEFTRAIT_TYPE (ADD_POINTER, "__add_pointer", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_ASSIGN, "__has_nothrow_assign", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_CONSTRUCTOR, "__has_nothrow_constructor", 1)
 DEFTRAIT_EXPR (HAS_NOTHROW_COPY, "__has_nothrow_copy", 1)
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 57840176863..e23693ab57f 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -12760,6 +12760,15 @@ finish_trait_type (cp_trait_kind kind, tree type1, tree type2,
 
   switch (kind)
     {
+    case CPTK_ADD_POINTER:
+      if (TREE_CODE (type1) == FUNCTION_TYPE
+	  && ((TYPE_QUALS (type1) & (TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE))
+	       || FUNCTION_REF_QUALIFIED (type1)))
+	return type1;
+      if (TYPE_REF_P (type1))
+	type1 = TREE_TYPE (type1);
+      return build_pointer_type (type1);
+
     case CPTK_REMOVE_CV:
       return cv_unqualified (type1);
 
diff --git a/gcc/testsuite/g++.dg/ext/add_pointer.C b/gcc/testsuite/g++.dg/ext/add_pointer.C
new file mode 100644
index 00000000000..3091510f3b5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/add_pointer.C
@@ -0,0 +1,37 @@
+// { dg-do compile { target c++11 } }
+
+#define SA(X) static_assert((X),#X)
+
+class ClassType { };
+
+SA(__is_same(__add_pointer(int), int*));
+SA(__is_same(__add_pointer(int*), int**));
+SA(__is_same(__add_pointer(const int), const int*));
+SA(__is_same(__add_pointer(int&), int*));
+SA(__is_same(__add_pointer(ClassType*), ClassType**));
+SA(__is_same(__add_pointer(ClassType), ClassType*));
+SA(__is_same(__add_pointer(void), void*));
+SA(__is_same(__add_pointer(const void), const void*));
+SA(__is_same(__add_pointer(volatile void), volatile void*));
+SA(__is_same(__add_pointer(const volatile void), const volatile void*));
+
+void f1();
+using f1_type = decltype(f1);
+using pf1_type = decltype(&f1);
+SA(__is_same(__add_pointer(f1_type), pf1_type));
+
+void f2() noexcept; // PR libstdc++/78361
+using f2_type = decltype(f2);
+using pf2_type = decltype(&f2);
+SA(__is_same(__add_pointer(f2_type), pf2_type));
+
+using fn_type = void();
+using pfn_type = void(*)();
+SA(__is_same(__add_pointer(fn_type), pfn_type));
+
+SA(__is_same(__add_pointer(void() &), void() &));
+SA(__is_same(__add_pointer(void() & noexcept), void() & noexcept));
+SA(__is_same(__add_pointer(void() const), void() const));
+SA(__is_same(__add_pointer(void(...) &), void(...) &));
+SA(__is_same(__add_pointer(void(...) & noexcept), void(...) & noexcept));
+SA(__is_same(__add_pointer(void(...) const), void(...) const));
diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
index 02b4b4d745d..56e8db7ac32 100644
--- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
+++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
@@ -2,6 +2,9 @@
 // { dg-do compile }
 // Verify that __has_builtin gives the correct answer for C++ built-ins.
 
+#if !__has_builtin (__add_pointer)
+# error "__has_builtin (__add_pointer) failed"
+#endif
 #if !__has_builtin (__builtin_addressof)
 # error "__has_builtin (__builtin_addressof) failed"
 #endif
-- 
2.43.0