Hello, On 31/07/2024 00:55, Jonathan Wakely wrote:
If __cpp_lib_is_virtual_base_of depends on __has_builtin, then that will do the right thing for #ifdef __cpp_lib_is_virtual_base_of in <type_traits>.
Third time's the charm, I hope; clang trunk seems to like this. Thank you, -- Giuseppe D'Angelo
From 7e81a94810692b1db3835227f3bc84464aef5df9 Mon Sep 17 00:00:00 2001
From: Giuseppe D'Angelo <giuseppe.dang...@kdab.com>
Date: Mon, 29 Jul 2024 19:23:54 +0200
Subject: [PATCH 2/2] libstdc++: add std::is_virtual_base_of
Added by P2985R0 for C++26. This simply exposes the compiler
builtin, and adds the feature-testing macro.
libstdc++-v3/ChangeLog:
* include/bits/version.def: Added the feature-testing macro.
* include/bits/version.h: Regenerated.
* include/std/type_traits: Add support for
std::is_virtual_base_of and std::is_virtual_base_of_v,
implemented in terms of the compiler builtin.
* testsuite/20_util/is_virtual_base_of/value.cc: New test.
Signed-off-by: Giuseppe D'Angelo <giuseppe.dang...@kdab.com>
---
libstdc++-v3/include/bits/version.def | 9 +++++
libstdc++-v3/include/bits/version.h | 10 ++++++
libstdc++-v3/include/std/type_traits | 14 ++++++++
.../20_util/is_virtual_base_of/value.cc | 34 +++++++++++++++++++
4 files changed, 67 insertions(+)
create mode 100644 libstdc++-v3/testsuite/20_util/is_virtual_base_of/value.cc
diff --git a/libstdc++-v3/include/bits/version.def b/libstdc++-v3/include/bits/version.def
index 42cdef2f526..6b8a5b89f29 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1814,6 +1814,15 @@ ftms = {
};
};
+ftms = {
+ name = is_virtual_base_of;
+ values = {
+ v = 202406;
+ cxxmin = 26;
+ extra_cond = "__has_builtin(__builtin_is_virtual_base_of)";
+ };
+};
+
// Standard test specifications.
stds[97] = ">= 199711L";
stds[03] = ">= 199711L";
diff --git a/libstdc++-v3/include/bits/version.h b/libstdc++-v3/include/bits/version.h
index 1eaf3733bc2..d884b019601 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2023,4 +2023,14 @@
#endif /* !defined(__cpp_lib_ranges_concat) && defined(__glibcxx_want_ranges_concat) */
#undef __glibcxx_want_ranges_concat
+#if !defined(__cpp_lib_is_virtual_base_of)
+# if (__cplusplus > 202302L) && (__has_builtin(__builtin_is_virtual_base_of))
+# define __glibcxx_is_virtual_base_of 202406L
+# if defined(__glibcxx_want_all) || defined(__glibcxx_want_is_virtual_base_of)
+# define __cpp_lib_is_virtual_base_of 202406L
+# endif
+# endif
+#endif /* !defined(__cpp_lib_is_virtual_base_of) && defined(__glibcxx_want_is_virtual_base_of) */
+#undef __glibcxx_want_is_virtual_base_of
+
#undef __glibcxx_want_all
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index c39a3792537..99656d863fa 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -51,6 +51,7 @@
#define __glibcxx_want_is_pointer_interconvertible
#define __glibcxx_want_is_scoped_enum
#define __glibcxx_want_is_swappable
+#define __glibcxx_want_is_virtual_base_of
#define __glibcxx_want_logical_traits
#define __glibcxx_want_reference_from_temporary
#define __glibcxx_want_remove_cvref
@@ -1539,6 +1540,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
: public __bool_constant<__is_base_of(_Base, _Derived)>
{ };
+#ifdef __cpp_lib_is_virtual_base_of // C++ >= 26
+ /// is_virtual_base_of
+ /// @since C++26
+ template<typename _Base, typename _Derived>
+ struct is_virtual_base_of
+ : public bool_constant<__builtin_is_virtual_base_of(_Base, _Derived)>
+ { };
+#endif
+
#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_convertible)
template<typename _From, typename _To>
struct is_convertible
@@ -3619,6 +3629,10 @@ template <typename _Tp>
#endif
template <typename _Base, typename _Derived>
inline constexpr bool is_base_of_v = __is_base_of(_Base, _Derived);
+#ifdef __cpp_lib_is_virtual_base_of // C++ >= 26
+template <typename _Base, typename _Derived>
+ inline constexpr bool is_virtual_base_of_v = __builtin_is_virtual_base_of(_Base, _Derived);
+#endif
#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_convertible)
template <typename _From, typename _To>
inline constexpr bool is_convertible_v = __is_convertible(_From, _To);
diff --git a/libstdc++-v3/testsuite/20_util/is_virtual_base_of/value.cc b/libstdc++-v3/testsuite/20_util/is_virtual_base_of/value.cc
new file mode 100644
index 00000000000..5d83de0683e
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_virtual_base_of/value.cc
@@ -0,0 +1,34 @@
+// { dg-do compile { target c++26 } }
+
+#include <type_traits>
+
+#if !defined(__cpp_lib_is_virtual_base_of) || __cpp_lib_is_virtual_base_of < 202406L
+#error "__cpp_lib_is_virtual_base_of should have been defined to 202406L or more"
+#endif
+
+class B { };
+class X : virtual public B { };
+class Y : virtual public B { };
+class Z : public B { };
+class AA : public X, public Y, public Z { };
+
+template<typename Base, typename Derived>
+constexpr bool test()
+{
+ constexpr bool t1 = std::is_virtual_base_of<Base, Derived>::value;
+ constexpr bool t2 = std::is_virtual_base_of_v<Base, Derived>;
+ static_assert(t1 == t2);
+ return t1;
+}
+
+void test01()
+{
+ static_assert(!test<B, B>());
+ static_assert( test<B, X>());
+ static_assert( test<B, Y>());
+ static_assert(!test<B, Z>());
+ static_assert( test<B, AA>());
+ static_assert(!test<X, AA>());
+ static_assert(!test<Y, AA>());
+ static_assert(!test<Z, AA>());
+}
--
2.34.1
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