PSS — C++ mapping for PSDL storage object references

There is a number of problems with the C++ mapping for storage object
references:

• abstract storage type references are mapped to abstract C++ classes;
  this implies that references are dynamically allocated and freed,
  and typically handled through pointers.

The dynamic allocation is expensive and error prone (risk of memory
leaks), and handling 'smart pointers' through pointers to these smart
pointers is very unusual.

• The mapped C++ classes inherit from each other, to mimic the implicit
  widening of regular pointers.
  Using inheritance for this purpose is a mistake, since it does not
  correspond to the behavior of real pointers – if class B derives
  from class A, a B instance is a A, but a B* is not a A*, it is only
  implictly converted into an A*.
  The correct way to provide this implicit widening is through
  conversion operators.

I propose to change the mapping and adopt concrete 'smart-pointer'
ref classes, that applications allocate on the stack. The proposed
mapping is implemented in Orbix2000 beta 2 (available from IONA
web site).

accepted