[clang][Interp] Pick right dynamic type when doing virtual calls (#101166)

Author: tbaederr

clang/lib/AST/Interp/Interp.h

@@ -2588,12 +2588,20 @@ inline bool CallVirt(InterpState &S, CodePtr OpPC, const Function *Func,
   size_t ThisOffset = ArgSize - (Func->hasRVO() ? primSize(PT_Ptr) : 0);
   Pointer &ThisPtr = S.Stk.peek<Pointer>(ThisOffset);
 
-  QualType DynamicType = ThisPtr.getDeclDesc()->getType();
-  const CXXRecordDecl *DynamicDecl;
-  if (DynamicType->isPointerType() || DynamicType->isReferenceType())
-    DynamicDecl = DynamicType->getPointeeCXXRecordDecl();
-  else
-    DynamicDecl = ThisPtr.getDeclDesc()->getType()->getAsCXXRecordDecl();
+  const CXXRecordDecl *DynamicDecl = nullptr;
+  {
+    Pointer TypePtr = ThisPtr;
+    while (TypePtr.isBaseClass())
+      TypePtr = TypePtr.getBase();
+
+    QualType DynamicType = TypePtr.getType();
+    if (DynamicType->isPointerType() || DynamicType->isReferenceType())
+      DynamicDecl = DynamicType->getPointeeCXXRecordDecl();
+    else
+      DynamicDecl = DynamicType->getAsCXXRecordDecl();
+  }
+  assert(DynamicDecl);
+
   const auto *StaticDecl = cast<CXXRecordDecl>(Func->getParentDecl());
   const auto *InitialFunction = cast<CXXMethodDecl>(Func->getDecl());
   const CXXMethodDecl *Overrider = S.getContext().getOverridingFunction(

clang/test/AST/Interp/records.cpp

@@ -1560,3 +1560,19 @@ namespace ArrayInitChain {
   static_assert(A[1].Width == 12, "");
   static_assert(A[1].Mask == 13, "");
 }
+
+#if __cplusplus >= 202002L
+namespace ctorOverrider {
+  // Ensure that we pick the right final overrider during construction.
+  struct A {
+    virtual constexpr char f() const { return 'A'; }
+    char a = f();
+  };
+
+  struct Covariant1 {
+    A d;
+  };
+
+  constexpr Covariant1 cb;
+}
+#endif