Re: Protected Types and Address Clauses

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <Dn44po.8ys@thomsoft.com> kst@thomsoft.com (Keith Thompson) writes:

  > Yes, the 'Address attribute is defined for HW_Control; in fact you can
  > refer to HW_Control'Address from within the body of Discretes.Write.
  > That doesn't mean an address *clause* for HW_Control is legal.
  > RM95-13.3(12) says that

  >     Address may be specified for stand-alone objects and for program
  >     units via an attribute_definition_clause.

  > Since HW_Control is not a stand-alone object, an address clause for it
  > is not legal, any more than an address clause is legal for a label or
  > an array element.

    Ah, but an address clause for Discretes should be legal, and in
fact it probably makes the most sense to put such an address clause
inside the protected object declaration.  (You could also put the same
declaration inside a protected type declaration, since at that
location the type name denotes the instance, but having more than one
object of that type at a time should always be erroneous.)

    However, locating the protected object may not be sufficient,
especially since there may be implementation specific data as part of
the object.  Does this mean you have to wrap the protected object in a
record and use a record representation clause?  Ugly, and still no
guarentee.  Best would be for implementations to either specify the
size of the implementation specific header, or to allocate the
implementation specific parts of a protected object after user
specified components.
--

					Robert I. Eachus

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