https://gcc.gnu.org/g:9fc5b8f956948e069d9b69ceed7316940bc798e2
commit r15-4087-g9fc5b8f956948e069d9b69ceed7316940bc798e2
Author: Giuseppe D'Angelo <giuseppe.dang...@kdab.com>
Date: Mon Jul 29 19:23:54 2024 +0200
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>
Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Diff:
---
libstdc++-v3/include/bits/version.def | 9 ++++++
libstdc++-v3/include/bits/version.h | 10 +++++++
libstdc++-v3/include/std/type_traits | 14 +++++++++
.../testsuite/20_util/is_virtual_base_of/value.cc | 34 ++++++++++++++++++++++
4 files changed, 67 insertions(+)
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index f2e28175b087..477651f358a2 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1807,6 +1807,15 @@ ftms = {
};
};
+ftms = {
+ name = is_virtual_base_of;
+ values = {
+ v = 202406;
+ cxxmin = 26;
+ extra_cond = "__has_builtin(__builtin_is_virtual_base_of)";
+ };
+};
+
ftms = {
name = ranges_concat;
values = {
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index dcd93fd432da..342ee6b4c7a0 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2000,6 +2000,16 @@
#endif /* !defined(__cpp_lib_fstream_native_handle) &&
defined(__glibcxx_want_fstream_native_handle) */
#undef __glibcxx_want_fstream_native_handle
+#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
+
#if !defined(__cpp_lib_ranges_concat)
# if (__cplusplus > 202302L)
# define __glibcxx_ranges_concat 202403L
diff --git a/libstdc++-v3/include/std/type_traits
b/libstdc++-v3/include/std/type_traits
index 6e6778078dcf..17ae2c435b38 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -53,6 +53,7 @@
#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
@@ -1541,6 +1542,15 @@ _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
@@ -3636,6 +3646,10 @@ 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 000000000000..5d83de0683e4
--- /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>());
+}
