Re: Record -> Array in Ada

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

In article <dmarshalDwFow7.4Fx@netcom.com> dmarshal@netcom.com (Dave Marshall) writes:

  > *FROWNERZ*, sometimes we are prevented from doing the cool things that
  > work.  LRM 13.5(8):

  > "Address clauses should not be used to achieve overlays of objects or
  > overlays or program units.  Nor should a given interrupt be linked to
  > more than one entry.  Any program using address clauses to achieve
  > such effects is erroneous."

   Hmmm.  If that statement prevents you from doing something that
works, try the Ada 95 wording:  "If an Address is specified, it is the
programmer's responsibility to ensure that the address is valid;
otherwise, program execution is erroneous."  There is no change in the
semantics from Ada 83 to Ada 95, just a realization that the meaning
of erroneous here exists only in the programmer's head.  If the
programmer defines the behavior as working, it is not erroneous, but
that determination is way outside the bounds of the RM.

   Also, in Ada 95 the Unchecked_Conversion approach is much better
defined.  But again, whether the actions correspond to the
programmer's intent is very implementation specific.  Unchecked
conversion of hidden fields and dope vectors can ruin your whole
day--or make your job easier.


--

					Robert I. Eachus

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