Re: Ada.Exceptions could be 'pragma Preelaborate' ?

[stt@houdini.camb.inmet.com (Tucker Taft)]

Stephen Leake (Stephen.Leake@gsfc.nasa.gov) wrote:

: Currently, Ada.Exceptions has no elaboration pragma, and thus any unit
: that 'withs' Ada.Exceptions cannot have 'pragma Preelaborate'. This is
: a pain; I'm building a nice library, everything is either Pure or
: Preelaborate, but then I start adding nice error messages to my
: exceptions, and I have to get rid of the pragmas. I started replacing
: Preelaborate with Elaborate_Body, and got some circular elaboration
: problems.

: So, is there a reason Ada.Exceptions can't be Preelaborate? nothing in
: the public spec violates a rule; do most implementations require
: something that does?

Probably RM95 should have erred on the side of putting too many
Preelaborate pragmas in, rather than too few.  Implementations
sometimes have to "cheat" anyway, so we shouldn't have worried
about that.  I think the rationale for not putting a Preelaborate
here was that it clearly depended on the run-time system, and
most run-time systems certainly need to do some kind of run-time
initialization.  However, it is permissible to raise exceptions
in a preelaborable package, so calling Raise_Exception explicitly
should be allowed as well.

This problem could probably be "fixed" pretty quickly by the
Ada Rapporteur Group as part of their language maintenance activities.  
We have already been looking into the general issue of "categorization" 
pragmas for run-time system packages.

Package Calendar is another one which should probably get
a Preelaborate pragma.  There probably aren't many language-defined
packages that shouldn't either have a pragma Pure or
a pragma Preelaborate.  A similar issue relates to the
Remote_Types pragma, for what it is worth...

: -- Stephe

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