[clang] Implement __is_pointer_interconvertible_base_of()

clang/docs/ReleaseNotes.rst

@@ -98,7 +98,8 @@ C++20 Feature Support
   behavior can use the flag '-Xclang -fno-skip-odr-check-in-gmf'.
   (#GH79240).
 
-- Implemented the `__is_layout_compatible` intrinsic to support
+- Implemented the `__is_layout_compatible` and `__is_pointer_interconvertible_base_of`
+  intrinsics to support
   `P0466R5: Layout-compatibility and Pointer-interconvertibility Traits <https://wg21.link/P0466R5>`_.
 
 - Clang now implements [module.import]p7 fully. Clang now will import module

clang/include/clang/Basic/TokenKinds.def

@@ -521,6 +521,7 @@ TYPE_TRAIT_1(__is_union, IsUnion, KEYCXX)
 TYPE_TRAIT_1(__has_unique_object_representations,
              HasUniqueObjectRepresentations, KEYCXX)
 TYPE_TRAIT_2(__is_layout_compatible, IsLayoutCompatible, KEYCXX)
+TYPE_TRAIT_2(__is_pointer_interconvertible_base_of, IsPointerInterconvertibleBaseOf, KEYCXX)
 
 #define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) KEYWORD(__##Trait, KEYCXX)
 #include "clang/Basic/TransformTypeTraits.def"

clang/include/clang/Sema/Sema.h

@@ -1975,6 +1975,8 @@ class Sema final : public SemaBase {
   };
 
   bool IsLayoutCompatible(QualType T1, QualType T2) const;
+  bool IsPointerInterconvertibleBaseOf(const TypeSourceInfo *Base,
+                                       const TypeSourceInfo *Derived);
 
   bool CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall,
                          const FunctionProtoType *Proto);

clang/lib/Sema/SemaChecking.cpp

@@ -19710,6 +19710,27 @@ bool Sema::IsLayoutCompatible(QualType T1, QualType T2) const {
   return isLayoutCompatible(getASTContext(), T1, T2);
 }
 
+//===-------------- Pointer interconvertibility ----------------------------//
+
+bool Sema::IsPointerInterconvertibleBaseOf(const TypeSourceInfo *Base,
+                                           const TypeSourceInfo *Derived) {
+  QualType BaseT = Base->getType()->getCanonicalTypeUnqualified();
+  QualType DerivedT = Derived->getType()->getCanonicalTypeUnqualified();
+
+  if (BaseT->isStructureOrClassType() && DerivedT->isStructureOrClassType() &&
+      getASTContext().hasSameType(BaseT, DerivedT))
+    return true;
+
+  if (!IsDerivedFrom(Derived->getTypeLoc().getBeginLoc(), DerivedT, BaseT))
+    return false;
+
+  // Per [basic.compound]/4.3, containing object has to be standard-layout.
+  if (DerivedT->getAsCXXRecordDecl()->isStandardLayout())
+    return true;
+
+  return false;
+}
+
 //===--- CHECK: pointer_with_type_tag attribute: datatypes should match ----//
 
 /// Given a type tag expression find the type tag itself.

clang/lib/Sema/SemaExprCXX.cpp

@@ -6082,6 +6082,22 @@ static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, const TypeSourceI
       Self.Diag(Rhs->getTypeLoc().getBeginLoc(), diag::err_vla_unsupported)
           << 1 << tok::kw___is_layout_compatible;
     return Self.IsLayoutCompatible(LhsT, RhsT);
+  }
+  case BTT_IsPointerInterconvertibleBaseOf: {
+    if (LhsT->isStructureOrClassType() && RhsT->isStructureOrClassType() &&
+        !Self.getASTContext().hasSameUnqualifiedType(LhsT, RhsT)) {
+      Self.RequireCompleteType(Rhs->getTypeLoc().getBeginLoc(), RhsT,
+                               diag::err_incomplete_type);
+    }
+
+    if (LhsT->isVariableArrayType())
+      Self.Diag(Lhs->getTypeLoc().getBeginLoc(), diag::err_vla_unsupported)
+          << 1 << tok::kw___is_pointer_interconvertible_base_of;
+    if (RhsT->isVariableArrayType())
+      Self.Diag(Rhs->getTypeLoc().getBeginLoc(), diag::err_vla_unsupported)
+          << 1 << tok::kw___is_pointer_interconvertible_base_of;
+
+    return Self.IsPointerInterconvertibleBaseOf(Lhs, Rhs);
   }
     default: llvm_unreachable("not a BTT");
   }

clang/test/SemaCXX/type-traits.cpp

@@ -1740,7 +1740,7 @@ void is_layout_compatible(int n)
   static_assert(!__is_layout_compatible(void, int));
   static_assert(__is_layout_compatible(void, const void));
   static_assert(__is_layout_compatible(void, volatile void));
-  static_assert(__is_layout_compatible(const int, volatile int));
+  static_assert(__is_layout_compatible(const void, volatile void));
   static_assert(__is_layout_compatible(int, int));
   static_assert(__is_layout_compatible(int, const int));
   static_assert(__is_layout_compatible(int, volatile int));
@@ -1839,6 +1839,95 @@ void is_layout_compatible(int n)
   static_assert(!__is_layout_compatible(EnumClassForward, int));
 }
 
+namespace IPIBO {
+struct Base {};
+struct Base2 {};
+struct Base3 : Base {};
+struct Base3Virtual : virtual Base {};
+struct Derived : Base {};
+struct DerivedIndirect : Base3 {};
+struct DerivedMultiple : Base, Base2 {};
+struct DerivedAmbiguous : Base, Base3 {};
+/* expected-warning@-1 {{direct base 'Base' is inaccessible due to ambiguity:
+    struct IPIBO::DerivedAmbiguous -> Base
+    struct IPIBO::DerivedAmbiguous -> Base3 -> Base}} */
+struct DerivedPrivate : private Base {};
+struct DerivedVirtual : virtual Base {};
+
+union Union {};
+union UnionIncomplete;
+struct StructIncomplete; // #StructIncomplete
+
+void is_pointer_interconvertible_base_of(int n)
+{
+  static_assert(__is_pointer_interconvertible_base_of(Base, Derived));
+  static_assert(!__is_pointer_interconvertible_base_of(Base2, Derived));
+  static_assert(__is_pointer_interconvertible_base_of(Base, DerivedIndirect));
+  static_assert(__is_pointer_interconvertible_base_of(Base, DerivedMultiple));
+  static_assert(!__is_pointer_interconvertible_base_of(Base3, DerivedMultiple));
+  static_assert(!__is_pointer_interconvertible_base_of(Base, DerivedAmbiguous));
+  static_assert(__is_pointer_interconvertible_base_of(Base, DerivedPrivate));
+  static_assert(!__is_pointer_interconvertible_base_of(Base, DerivedVirtual));
+  static_assert(!__is_pointer_interconvertible_base_of(Union, Union));
+  static_assert(!__is_pointer_interconvertible_base_of(UnionIncomplete, UnionIncomplete));
+  static_assert(__is_pointer_interconvertible_base_of(StructIncomplete, StructIncomplete));
+  static_assert(__is_pointer_interconvertible_base_of(StructIncomplete, const StructIncomplete));
+  static_assert(__is_pointer_interconvertible_base_of(StructIncomplete, volatile StructIncomplete));
+  static_assert(__is_pointer_interconvertible_base_of(const StructIncomplete, volatile StructIncomplete));
+  static_assert(!__is_pointer_interconvertible_base_of(StructIncomplete, Derived));
+  static_assert(!__is_pointer_interconvertible_base_of(Base, StructIncomplete));
+  // expected-error@-1 {{incomplete type 'StructIncomplete' where a complete type is required}}
+  //   expected-note@#StructIncomplete {{forward declaration of 'IPIBO::StructIncomplete'}}
+  static_assert(!__is_pointer_interconvertible_base_of(CStruct2, CppStructNonStandardByBase2));
+  static_assert(!__is_pointer_interconvertible_base_of(void, void));
+  static_assert(!__is_pointer_interconvertible_base_of(void, int));
+  static_assert(!__is_pointer_interconvertible_base_of(void, const void));
+  static_assert(!__is_pointer_interconvertible_base_of(void, volatile void));
+  static_assert(!__is_pointer_interconvertible_base_of(const void, volatile void));
+  static_assert(!__is_pointer_interconvertible_base_of(int, int));
+  static_assert(!__is_pointer_interconvertible_base_of(int, const int));
+  static_assert(!__is_pointer_interconvertible_base_of(int, volatile int));
+  static_assert(!__is_pointer_interconvertible_base_of(const int, volatile int));
+  static_assert(!__is_pointer_interconvertible_base_of(int *, int * __restrict));
+  static_assert(!__is_pointer_interconvertible_base_of(int, _Atomic int));
+  static_assert(!__is_pointer_interconvertible_base_of(_Atomic(int), _Atomic int));
+  static_assert(!__is_pointer_interconvertible_base_of(int, unsigned int));
+  static_assert(!__is_pointer_interconvertible_base_of(char, unsigned char));
+  static_assert(!__is_pointer_interconvertible_base_of(char, signed char));
+  static_assert(!__is_pointer_interconvertible_base_of(unsigned char, signed char));
+  using function_type = void();
+  using function_type2 = void(char);
+  static_assert(!__is_pointer_interconvertible_base_of(const function_type, const function_type));
+  // expected-warning@-1 {{'const' qualifier on function type 'function_type' (aka 'void ()') has no effect}}
+  // expected-warning@-2 {{'const' qualifier on function type 'function_type' (aka 'void ()') has no effect}}
+  static_assert(!__is_pointer_interconvertible_base_of(function_type, const function_type));
+  // expected-warning@-1 {{'const' qualifier on function type 'function_type' (aka 'void ()') has no effect}}
+  static_assert(!__is_pointer_interconvertible_base_of(const function_type, const function_type2));
+  // expected-warning@-1 {{'const' qualifier on function type 'function_type' (aka 'void ()') has no effect}}
+  // expected-warning@-2 {{'const' qualifier on function type 'function_type2' (aka 'void (char)') has no effect}}
+  static_assert(!__is_pointer_interconvertible_base_of(int CStruct2::*, int CStruct2::*));
+  static_assert(!__is_pointer_interconvertible_base_of(int CStruct2::*, char CStruct2::*));
+  static_assert(!__is_pointer_interconvertible_base_of(void(CStruct2::*)(int), void(CStruct2::*)(int)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(CStruct2::*)(int), void(CStruct2::*)(char)));
+  static_assert(!__is_pointer_interconvertible_base_of(int[], int[]));
+  static_assert(!__is_pointer_interconvertible_base_of(int[], double[]));
+  static_assert(!__is_pointer_interconvertible_base_of(int[2], int[2]));
+  static_assert(!__is_pointer_interconvertible_base_of(int[n], int[2]));
+  // expected-error@-1 {{variable length arrays are not supported in '__is_pointer_interconvertible_base_of'}}
+  static_assert(!__is_pointer_interconvertible_base_of(int[n], int[n]));
+  // expected-error@-1 {{variable length arrays are not supported in '__is_pointer_interconvertible_base_of'}}
+  // expected-error@-2 {{variable length arrays are not supported in '__is_pointer_interconvertible_base_of'}}
+  static_assert(!__is_pointer_interconvertible_base_of(int&, int&));
+  static_assert(!__is_pointer_interconvertible_base_of(int&, char&));
+  static_assert(!__is_pointer_interconvertible_base_of(void(int), void(int)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(int), void(char)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(&)(int), void(&)(int)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(&)(int), void(&)(char)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(*)(int), void(*)(int)));
+  static_assert(!__is_pointer_interconvertible_base_of(void(*)(int), void(*)(char)));
+}
+}
+
 void is_signed()
 {
   //static_assert(__is_signed(char));