Re: Safety of the Booch Ada 95 Components

["Robert I. Eachus" <eachus@mitre.org>]

Hyman Rosen wrote:
 
> Why is an assignment operator that raises an exception broken?

   It isn't.  But in Ada, an assignment that raises an exception does so
before actually "copying the bits."  So that objects that were
consistant are not broken except by an explicit abort from some other
task while outside an abort-deferred region.  However, one explicit
abort-deferred operation is: "an assignment operation to an object with
a controlled part." RM9.8(11)  There other such operations included so
that a user of an object of a controlled type can expect that the value
is never corrupted.

   So any user of an Ada package which did corrupt objects in this
manner would be consider it to be broken.
 
-- 

                                        Robert I. Eachus

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