[libcxx-commits] [libcxx] [libc++] Implement P2985R0: std::is_virtual_base_of (PR #105847)

[Nikolas Klauser via libcxx-commits]

================
@@ -26,6 +26,19 @@ template <class _Bp, class _Dp>
 inline constexpr bool is_base_of_v = __is_base_of(_Bp, _Dp);
 #endif
 
+#if _LIBCPP_STD_VER >= 26
+#  if __has_builtin(__builtin_is_virtual_base_of)
+
+template <class _Base, class _Derived>
+struct _LIBCPP_TEMPLATE_VIS is_virtual_base_of
+    : public integral_constant<bool, __builtin_is_virtual_base_of(_Base, _Derived)> {};
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philnik777 wrote:

```suggestion
    : public bool_constant<__builtin_is_virtual_base_of(_Base, _Derived)> {};
```

https://github.com/llvm/llvm-project/pull/105847