Version 1.1.1.1 of ais/ai-00114.txt

Unformatted version of ais/ai-00114.txt version 1.1.1.1
Other versions for file ais/ai-00114.txt

!standard 12.03 (11)          96-10-04 AI95-00114/00
!class confirmation 96-04-04
!status work item 96-04-10
!status received 96-04-04
!priority Low
!difficulty Hard
!subject Editorial Comments on AARM
!summary 96-04-04
This AI serves as a holder for editorial comments on AARM-only annotations. Because the AARM has no official status as far as ISO is concerned, these will be considered low priority.
!question 96-04-04
!response 96-04-04
!appendix

!section 12.3(11)
!subject but the{y} can be in instances.
!reference AARM95-12.3(11.x)
!from Keith Thompson 95-11-10
!reference 95-5384.a Keith Thompson 95-11-11>>
!discussion

****************************************************************

!section 12.3(11)
!subject It doesn't matter that [an] one could imagine ...
!reference AARM-12.3(11.dd)
!from Keith Thompson 95-11-17
!reference 95-5391.a Keith Thompson 95-11-17>>

****************************************************************

!section 13.3(12)
!subject Address clauses for components
!reference AARM95-13.3(12)
!from Keith Thompson 96-02-22
!reference 96-5429.a Keith Thompson 96-2-22>>
!discussion

The referenced paragraph in the AARM says:

        12   {specifiable [of Address for stand-alone objects and for
        program units]} {Address clause} Address may be specified for
        [stand-alone] objects and for program units via an attribute_
        definition_clause.

The use of square brackets around the phrase "stand-alone" implies that it
is redundant and can be proven from other rules.  How does the restriction
to stand-alone objects follow from other rules?  In particular, why is
this illegal (adapted from a posting to comp.lang.ada by Bob Gilbert)?

   protected Discretes is 
      procedure Write(Settings : in Setting_List);
   private
      HW_Control : Discrete_HW_Control;
      for HW_Control use at Some_Legal_Address;
   end Discretes;

I'm not suggesting that it should be, just asking how it can be proven
from other rules.


****************************************************************

!section 13.1(14)
!subject Errors in example
!reference RM95-13.1(14)
!from Jorgen Bundgaard 96-03-07
!keywords
!reference 96-5434.a Joergen Bundgaard 96-3-7>>
!discussion

The example 13.1(14.c-e) contains other violations of the legality rules than
those marked with "-- Illegal!": types A1 and A2 should be general access
types, and the accessibility levels of the Obj1(17) and Obj2(17) should not be
statically deeper than that of access types A2 and A1, respectively.

****************************************************************

!section 13.3(12)
!subject Address clauses for components
!reference AARM95-13.3(12)
!reference 96-5429.a Keith Thompson 96-2-22
!from Bob Duff
!reference 96-5456.a Robert A Duff 96-4-8>>
!discussion

> The referenced paragraph in the AARM says:
> 
>       12   {specifiable [of Address for stand-alone objects and for
>       program units]} {Address clause} Address may be specified for
>       [stand-alone] objects and for program units via an attribute_
>       definition_clause.
> 
> The use of square brackets around the phrase "stand-alone" implies that it
> is redundant and can be proven from other rules.  How does the restriction
> to stand-alone objects follow from other rules?

Good question.

Apparently, we thought that it was implied by 13.1(6.a):

        6.a   Ramification:  The ``statically denote'' part implies that it
        is impossible to specify the representation of an object that is not
        a stand-alone object, except in the case of a representation item
        like pragma Atomic that is allowed inside a component_list (in which
        case the representation item specifies the representation of
        components of all objects of the type).  It also prevents the problem
        of renamings of things like ``P.all'' (where P is an
        access-to-subprogram value) or ``E(I)'' (where E is an entry family).

But I must admit that I don't see how this follows from the RM.

In any case, the square brackets are AARM-only material, so the ARG can
safely believe them, even if they don't strictly follow from other
rules.  That is, this is a bug in the AARM's use of brackets, but not a
bug in the RM itself.

>...  In particular, why is
> this illegal (adapted from a posting to comp.lang.ada by Bob Gilbert)?
> 
>    protected Discretes is 
>       procedure Write(Settings : in Setting_List);
>    private
>       HW_Control : Discrete_HW_Control;
>       for HW_Control use at Some_Legal_Address;
>    end Discretes;
> 
> I'm not suggesting that it should be, just asking how it can be proven
> from other rules.

The above was intended to be illegal, and *is* illegal by 13.3(12),
despite its use of square brackets in the AARM.

Anwyay, I think this can be taken as an editorial comment on the AARM,
rather than a comment on the RM itself.

- Bob

****************************************************************

!section 13.3(12)
!subject Address clauses for components
!reference AARM95-13.3(12)
!reference 96-5429.a Keith Thompson 96-2-22
!reference 96-5456.a Bob Duff 96-03-08
!from Keith Thompson
!reference 96-5458.a Keith Thompson 96-4-8>>
!discussion

Bob Duff wrote:
> In any case, the square brackets are AARM-only material, so the ARG can
> safely believe them, even if they don't strictly follow from other
> rules.  That is, this is a bug in the AARM's use of brackets, but not a
> bug in the RM itself.
[...]
> Anwyay, I think this can be taken as an editorial comment on the AARM,
> rather than a comment on the RM itself.

I agree.  I hadn't realized (though I probably should have) that the
phrase "stand-alone" does appear in the RM, without the brackets.

****************************************************************

!section 7.3(7)
!subject Semantic Errors in AARM 7.3 Examples
!reference AARM-7.3(7.f)
!reference AARM-7.3(7.h)
!reference AARM-7.3(7.m)
!from Ivan B. Cvar 96-08-01
!reference 96-5629.a Ivan B. Cvar 96-8-1>>
!discussion

There are 3 unintended semantic errors in Annotated Ada 95 Reference Manual
clause 7.3, paragraphs 7.f, 7.h, and 7.m.  They are:

In the example of 7.3(7.f), the closing designator at the end of the
body of procedure Foo is wrong.  It should be Foo, not A.

In the example of 7.3(7.h), the named association in the discriminant
constraint denotes a discriminant named A, whereas the correct name is D,
as declared in paragraph 7.g.

In the example of 7.3(7.m), the package Q should have the context clause
"with P; use P" to make the name of type Parent visible, and for consistency
with 7.3(7.n) since 7.3(7.n) contains a with clause that denotes Q.

****************************************************************

!section 3.9.2(20)
!subject Illegal use of names in 3.9.2 example
!reference AARM95-3.9.2(20.e)
!from Ivan B. Cvar 96-09-19
!keywords dispatching operations
!reference 96-5703.a Ivan B. Cvar 96-9-19>>
!discussion

The example in the Annotated Ada95 Reference Manual 3.9.2(20.e) fails
to compile because it references 2 type names that are not visible at
the point of use.

However, the meaning of the example is clear, despite the errors, but you
may want to repair the example for future releases.

with P1; with P2;
procedure Main is
    X : T2;                  --<<< ERROR: Should be P2.T2
    Y : T1'Class := X;       --<<< ERROR: Should be P1.T1
begin
    P2.Op_A(Param => X); -- Nondispatching call.
    P1.Op_A(Arg => Y); -- Dispatching call.
    P2.Op_B(Arg => X); -- Nondispatching call.
    P1.Op_B(Arg => Y); -- Dispatching call.
end Main;



****************************************************************

Questions? Ask the ACAA Technical Agent