Issue 2309:  Memory management of recursive value (cxx_revision)
Source:  (, )
Nature:  Uncategorized Issue
Severity: 
Summary: Summary: Section 20.21, "Argument Passing Considerations," says that for valuetypes:
      "The caller shall eventually invoked _remove_ref on the valuetype
 instance it receives back as either an inout, out, or return value."
 
 For memory management purposes, this is not sufficient in some cases.
 
 

Resolution: 
Revised Text: 
Actions taken:
January 20, 1999: received issue
Discussion: 
deferred in June 2011 to the next RTF
End of Annotations:=====
From: mcheng@us.ibm.com
X-Lotus-FromDomain: IBMUS
To: issues@omg.org, cxx_revision@omg.org
Date: Wed, 20 Jan 1999 11:45:28 -0600
Subject: memory management of recursive value
Content-Disposition: inline




Section 20.21, "Argument Passing Considerations," says that for
valuetypes:
     "The caller shall eventually invoked _remove_ref on the valuetype
instance it receives back as either an inout, out, or return value."

For memory management purposes, this is not sufficient in some cases.
Consider a circularly linked list:
   valuetype val {
        public val next;
    };


    val * myVal = new ...;   // initial ref count 1
    myVal->next(myVal);                    // Introducing circular
link to
self, ref count now 2

If myVal were passed back to a caller, calling _remove_ref() merely
decreases its ref count to 1, causing a memory leak.   This leak can
happen
in the dispatcher to a method that returns a valuetype, or in the
destructor of a struct/union/sequence that holds a valuetype member.

Michael Cheng
mcheng@us.ibm.com