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<type_traits>: Partially unblock P0466R5 for Clang #5621

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Merged
merged 6 commits into from
Oct 4, 2025
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Merged

<type_traits>: Partially unblock P0466R5 for Clang #5621

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0ef501f
Partially unblock P0466R5 for Clang
frederick-vs-ja Jun 24, 2025
a0f4c41
Merge branch 'microsoft:main' into p0466r5-clang-19
frederick-vs-ja Aug 17, 2025
865e5bd
Merge branch 'microsoft:main' into p0466r5-clang-19
frederick-vs-ja Aug 27, 2025
fe8688a
Merge branch 'microsoft:main' into p0466r5-clang-19
frederick-vs-ja Sep 16, 2025
1da1018
Merge branch 'main' into p0466r5-clang-19 (add `_NO_SPECIALIZATIONS_O…
StephanTLavavej Oct 3, 2025
388715b
Avoid redundantly testing `defined(__clang__)`.
StephanTLavavej Oct 3, 2025
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15 changes: 14 additions & 1 deletion stl/inc/type_traits
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Original file line number Diff line number Diff line change
Expand Up @@ -1968,21 +1968,34 @@ _NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_nothrow_invocable_r_v =
#endif // _HAS_CXX17

#if _HAS_CXX20
#ifndef __clang__ // TRANSITION, LLVM-48860
#if !defined(__clang__) || defined(__EDG__) \
|| __clang_major__ >= 19 // TRANSITION, VSO-2397560 (RWC relying on ancient Clang)
_EXPORT_STD template <class _Ty1, class _Ty2>
struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS is_layout_compatible : bool_constant<__is_layout_compatible(_Ty1, _Ty2)> {};

_EXPORT_STD template <class _Ty1, class _Ty2>
_NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_layout_compatible_v = __is_layout_compatible(_Ty1, _Ty2);

#if !defined(__clang__) || defined(__EDG__) // TRANSITION, LLVM-135273
_EXPORT_STD template <class _Base, class _Derived>
struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS is_pointer_interconvertible_base_of
: bool_constant<__is_pointer_interconvertible_base_of(_Base, _Derived)> {};

_EXPORT_STD template <class _Base, class _Derived>
_NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_pointer_interconvertible_base_of_v =
__is_pointer_interconvertible_base_of(_Base, _Derived);
#else // ^^^ no workaround / workaround vvv
_EXPORT_STD template <class _Base, class _Derived>
struct _NO_SPECIALIZATIONS_OF_TYPE_TRAITS is_pointer_interconvertible_base_of
: bool_constant<__is_pointer_interconvertible_base_of(remove_cv_t<_Base>, remove_cv_t<_Derived>)> {};

_EXPORT_STD template <class _Base, class _Derived>
_NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_pointer_interconvertible_base_of_v =
__is_pointer_interconvertible_base_of(remove_cv_t<_Base>, remove_cv_t<_Derived>);
#endif // ^^^ workaround ^^^
#endif // ^^^ no workaround ^^^

#ifndef __clang__ // TRANSITION, LLVM-48860
_EXPORT_STD template <class _ClassTy, class _MemberTy>
_NODISCARD _NO_SPECIALIZATIONS_OF_TYPE_TRAITS constexpr bool is_pointer_interconvertible_with_class(
_MemberTy _ClassTy::* _Pm) noexcept {
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30 changes: 26 additions & 4 deletions tests/std/tests/P0466R5_layout_compatibility_and_pointer_interconvertibility_traits/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ struct S { // Must be declared at namespace scope due to static data member
};

constexpr bool test() {
#if defined(__cpp_lib_is_layout_compatible) && defined(__cpp_lib_is_pointer_interconvertible) // TRANSITION, LLVM-48860
// is_layout_compatible tests
{
struct S0 {
Expand Down Expand Up @@ -42,14 +41,28 @@ constexpr bool test() {
int v1;

private:
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-private-field"
#endif // defined(__clang__)
int v2;
#ifdef __clang__
#pragma clang diagnostic pop
#endif // defined(__clang__)
};

struct S5 {
int v1;

private:
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-private-field"
#endif // defined(__clang__)
int v2;
#ifdef __clang__
#pragma clang diagnostic pop
#endif // defined(__clang__)
};

enum E1 { e1, e2, e3, e4 };
Expand Down Expand Up @@ -94,13 +107,21 @@ constexpr bool test() {
int : 0;
};
class D : public C {};
// Disable warning C4408: anonymous union did not declare any data members
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wmissing-declarations"
#else // ^^^ defined(__clang__) / !defined(__clang__) vvv
#pragma warning(push)
#pragma warning(disable : 4408)
#pragma warning(disable : 4408) // C4408: anonymous union did not declare any data members
#endif // ^^^ !defined(__clang__) ^^^
class E : public A {
union {};
};
#ifdef __clang__
#pragma clang diagnostic pop
#else // ^^^ defined(__clang__) / !defined(__clang__) vvv
#pragma warning(pop)
#endif // ^^^ !defined(__clang__) ^^^
class F : private A {}; // Non-public inheritance
class NS : public B, public C {}; // Non-standard layout
class I; // Incomplete
Expand Down Expand Up @@ -134,6 +155,7 @@ constexpr bool test() {
ASSERT(!is_pointer_interconvertible_base_of_v<U, I>);
}

#ifndef __clang__ // TRANSITION, LLVM-48860
// is_corresponding_member tests
{
struct S1 {
Expand Down Expand Up @@ -238,7 +260,7 @@ constexpr bool test() {
ASSERT(!is_pointer_interconvertible_with_class(&C::f1));
ASSERT(!is_pointer_interconvertible_with_class(static_cast<int A::*>(nullptr)));
}
#endif // ^^^ defined(__cpp_lib_is_layout_compatible) && defined(__cpp_lib_is_pointer_interconvertible) ^^^
#endif // ^^^ no workaround ^^^
return true;
}

Expand Down