Rationale for Ada 2005

John Barnes

9.2 Retrospective changes to Ada 95

In the course of the development of Ada 2005, a number of small changes were deemed to apply also to Ada 95 and thus were classified as binding interpretations rather than amendments. Accordingly they are not (generally) covered by the changes discussed in the previous chapters. Note however, that AI-241 on exceptions was discussed in chapter 6 even though it was eventually classified as a binding interpretation. Moreover, AI-329 was split and the part stating that Raise_Exception never returns (also applying to Ada 95) was formed into AI-446.

AI-438 adds subprograms Read_Exception_Occurrence and Write_Exception_Occurence plus corresponding attribute definition clauses for streams to the package Ada.Exceptions thus

procedure Read_Exception_Occurrence
(Stream: not null access Root_Stream_Type'Class; Item: out Exception_Occurrence);

procedure Write_Exception_Occurrence
(Stream: not null access Root_Stream_Type'Class; Item: in Exception_Occurrence);

for Exception_Occurrence'Read use Read_Exception_Occurrence;

for Exception_Occurrence'Write use Write_Exception_Occurrence;

These attributes enable the type Exception_Occurrence to be streamed. Note that this is a limited type and so streaming is only possible if predefined. A survey of other existing and new predefined limited types showed that no others needed to be treated in this way.

No other retrospective AIs actually affect the specification of any units but typically add or correct a number of rules. Of these some are of special interest because they introduce minor incompatibilities or inconsistencies. They are

108

Inheritance of stream attributes for type extensions

(108 was actually in the 2001 Corrigendum)

133

Controlling bit ordering

195

Streams (this covers many issues regarding streams)

220

Subprograms withing private compilation units

225

Aliased current instance for limited types

229