488858 - List isn't copy safe

Status: VERIFIED FIXED

(Tamarin Graveyard :: Virtual Machine, defect)

Description

[Tommy Reilly]

Attachments: 	
Hi Tommy -

I was debugging a crash and noticed that someone had incorrectly written:

  struct blah {};  // unmanaged

  class foo : MMgc::GCFinalizedObject
  {
    avmplus::List<blah*> m_list;

    void set(const amvplus::List<blah*> otherList)
    {
      m_list = otherList;  // WRONG, no operator=
    }

    void set2(const avmplus::List<blah*> otherList)
    {
      m_list.clear();
      m_list.add(otherList);  // RIGHT
    }
  };

The symptom was hard to identify at first - m_list.data was double-freed because the automatically provided bitwise-copy operator= just duplicated the data pointer.  Poisoned memory helped me figure it out (thank you).

What I'm wondering is: should we make it a compile error to use operator= with avmplus::List?  Presumably by providing a private operator=?  I'd be happy to do the work (easy), but I'm not sure what the procedure is for getting something into avmplus, and also I could be missing some reason why this is a dumb idea.

Thanks
d.

Comment 1

[Tommy Reilly]

we either need a copy ctor that makes a copy or make it private and force client to use add

Comment 2

[Rick Reitmaier]

vote for compile error

Comment 3

[Lars T Hansen]

vote for compile error

Comment 4

[Steven Johnson]

(In reply to comment #3)
> vote for compile error

+1

Comment 5

[Lars T Hansen]

Attachment: Trivial patch, v1

Hides both the copy constructor and the assignment operator.

Comment 6

[Lars T Hansen]

redux changeset:   2070:6ad0961dbd41