[PATCH] D49985: [ADT] ImmutableList no longer requires elements to be copy constructible

[Umann Kristóf via Phabricator via llvm-commits]

Szelethus added a comment.

I ran into a serious problem. It seems like `ImmutableList` doesn't run the destructor for `std::unique_ptr`s or `std::shared_ptr`s:

  struct Obj {
    ~Obj() { llvm_unreachable(""); } // never called
  };
  
  using ObjRef = std::unique_ptr<Obj>; // same with std::shared_ptr
  
  namespace llvm {
  
  // Specializing FoldingSetTrait so we can store ObjRef objects in ImmutableList.
  template <>
  struct FoldingSetTrait<ObjRef> : public DefaultFoldingSetTrait<ObjRef> {
  
    static void Profile(const ObjRef &FN, FoldingSetNodeID &ID) {
      ID.AddPointer(FN.get());
    }
  };
  
  } // end of namespace llvm
  
  TEST_F(ImmutableListTest, UniquePtrTest) {
    ImmutableList<ObjRef>::Factory f;
    ImmutableList<ObjRef> L = f.create(ObjRef(new Obj));
  }

What is very interesting though, a simple wrapper works perfectly:

  struct ObjRef {
    Obj *ptr;
    ObjRef(Obj *ptr) : ptr(ptr) {}
    ~ObjRef() { delete ptr; }
    Obj *get() const { return ptr; }
  };
  // llvm_unreachable is actually reached in Obj::~Obj().

I've been stuck on this issue for a while now. Do you know anything about why this could happen?


https://reviews.llvm.org/D49985