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libstdc++: add std::is_virtual_base_of

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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.dangelo@kdab.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This commit is contained in:
Giuseppe D'Angelo 2024-07-29 19:23:54 +02:00 • committed by Patrick Palka
parent 7c0d1e9f2a
commit 9fc5b8f956
4 changed files with 67 additions and 0 deletions
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9
libstdc++-v3/include/bits/version.def
View file

@ -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 = {

10
libstdc++-v3/include/bits/version.h
View file

@ -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

14
libstdc++-v3/include/std/type_traits
View file

@ -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);

34
libstdc++-v3/testsuite/20_util/is_virtual_base_of/value.cc Normal file
View file

@ -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>());
}