Re: Size and pack

["Jeff Creem" <jeff@thecreems.com>]

See..I knew it was too early when I wrote that. I checked and GNAT rejects
it as well without the pragma pack.
VADS allowed it however that was an Ada 83 implementation.

In any case I stand by my basic premise that Roberts response was correct
when
limited to the scope of the thread (which was talking about record rep
clauses) however
it was too broad when taken out of context since the pragma pack should
indeed
by used on the array when one wants to pack the items of the array.


As for the "Standardization" troll comment..There are many things in the
standard
that are not directly specified or are specified in terms of dependencies on
the
host architecture. (Word size, etc).. This is not Java. There is no standard
Ada
virtual machine that forces all applications to run 5-30 times slower than
a native implementation (see I can troll too!).


"Adrian Hoe" <byhoe@greenlime.com> wrote in message
news:9ff447f2.0110311758.2be52637@posting.google.com...
> "Jeff Creem" <jeff@thecreems.com> wrote in message
news:<nHRD7.162473$vq.40258001@typhoon.ne.mediaone.net>...
> > OK.. I know I am going to regret this since whenever I question Robert I
> > usually am wrong however
> > without using the complete context of this thread, I believe Roberts
> > statement is actually
> > a little too broad. There ARE indeed times when you want a pragma pack
and a
> > rep spec. Not for the record case but for arrays of items that have been
rep
> > spec'ed.
> >
> > for example, the code fragment
> >
> > type My_Type is range 0 .. 3;
> > for My_Type'size use 2;
> >
> > type My_Array is array (1 .. 4) of My_Type;
> > pragma Pack (My_Array); -- Without this the following could fail
> > for My_Array'size use 8;
> >
> >
> > The pragma pack is needed I believe because the rep spec on My_Array can
> > be rejected without it (At least it has been rejected by some compilers
and
> > I forget
> > the exact rule but it had something to do with the final rep spec not
being
> > allowed to
> > change the layout of the items within the array).
> >
> > Having said that VADS used to compile this without the pragma pack.
Green
> > Hills did not.
> > I *THINK* GNAT does allow it to go through without the rep spec for
several
> > versions now.
>
>
> But, why the differenct implementation by these compilers' vendors? I
> thought Ada is a standardized language regardless of platforms. Of
> course, a problem like whether to use "pragma pack" or not in the
> above Jeff's example "supposed" not to arise if Ada is standardized.
>
> Oh... I am getting quite confusing now, and not to mention Ada
> newbies!
>
>
>
> >
> > "Robert Dewar" <dewar@gnat.com> wrote in message
> > news:5ee5b646.0110301750.38ba5bfd@posting.google.com...
> > > john.mccabe@emrad.com.nospam (John McCabe) wrote in message
> >  news:<3bc41989.4285341@news.demon.co.uk>...
> > > > Your best bet would be to use as many representation attributes as
are
> > > > necessary. In general I would use both a representation clause and
> > > > pragma pack
> > >
> > > No, that's pointless, if you use a complete rep clause, then it is
> > > redundant to use pragma Pack since it won't have
> > > any effect.