llvm-project

faef8b4a - [webkit.RefCntblBaseVirtualDtor] Allow CRTP classes without a virtual destructor. (#92837)

[webkit.RefCntblBaseVirtualDtor] Allow CRTP classes without a virtual destructor. (#92837) Exempt CRTP (Curiously Recurring Template Pattern) classes with a delete operation acting on "this" pointer with an appropriate cast from the requirement that a ref-countable superclass must have a virtual destructor. To do this, this PR introduces new DerefFuncDeleteExprVisitor, which looks for a delete operation with an explicit cast to the derived class in a base class. This PR also changes the checker so that we only check a given class's immediate base class instead of all ancestor base classes in the class hierarchy. This is sufficient because the checker will eventually see the definition for every class in the class hierarchy and transitively proves every ref-counted base class has a virtual destructor or deref function which casts this pointer back to the derived class before deleting. Without this change, we would keep traversing the same list of base classes whenever we encounter a new subclass, which is wholly unnecessary. It's possible for DerefFuncDeleteExprVisitor to come to a conclusoin that there isn't enough information to determine whether a given templated superclass invokes delete operation on a subclass when the template isn't fully specialized for the subclass. In this case, we return std::nullopt in HasSpecializedDelete, and visitCXXRecordDecl will skip this declaration. This is okay because the checker will eventually see a concreate fully specialized class definition if it ever gets instantiated.