!standard H.4(20/2)                                      19-02-26  AI12-0318-1/02
!standard H.4(24/3)
!class binding interpretation 19-02-22
!status Amendment 1-2012 19-02-26
!status WG9 Approved 22-06-22
!status ARG Approved 10-0-0  19-02-26
!status work item 19-02-22
!status received 19-02-14
!priority Low
!difficulty Easy
!qualifier Omission
!subject No_IO should apply to Ada.Directories 
!summary

Ada.Directories is added to the list of packages not allowed by restriction 
No_IO.

!question

Restriction No_IO (see H.4) includes a list of packages that aren't allowed.
But Ada.Directories isn't on that list. Should it be on the list? (Yes.)

!recommendation

(See Summary.)

!wording

Modify H.4(20/2):

Semantic dependence on any of the library units Sequential_IO, Direct_IO, 
Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, [or] Stream_IO{, or Directories} is 
not allowed. 

Modify H.4(24/3):

If an implementation supports pragma Restrictions for a particular argument, 
then except for the restrictions [No_Unchecked_Deallocation, 
No_Unchecked_Conversion, ]No_Access_Subprograms, No_Unchecked_Access, 
No_Specification_of_Aspect, No_Use_of_Attribute, No_Use_of_Pragma, 
{No_Dependence => Ada.Unchecked_Conversion, }and [the equivalent use of]
No_Dependence {=> Ada.Unchecked_Deallocation}, the associated restriction 
applies to the run-time system. 

Delete AARM H.4(24.e/3).

!discussion

The modification to H.4(24/3) is to eliminate obsolescent restrictions from 
the rule; we generally do not mention Annex J features in the rest of the 
Standard. Since the runtime does not have to be written in Ada anyway, it is 
only the effect, and not the specific restrictions used, that matters. Thus
there is no need to mention the Annex J restrictions here.

The AARM note is explaining the old wording means essentially what the new 
wording says explicitly, there is no need for it now.

!corrigendum H.4(20/2)

@drepl
@xhang<@xterm<No_IO>
Semantic dependence on any of the library units Sequential_IO, Direct_IO,
Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO is not allowed.>
@dby
@xhang<@xterm<No_IO>
Semantic dependence on any of the library units Sequential_IO, Direct_IO,
Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, Stream_IO, or Directories is not 
allowed.>

!corrigendum H.4(24/3)

@drepl
If an implementation supports @fa<pragma> Restrictions for a particular 
argument, then except for the restrictions No_Unchecked_Deallocation, 
No_Unchecked_Conversion, No_Access_Subprograms, No_Unchecked_Access, 
No_Specification_of_Aspect, No_Use_of_Attribute, No_Use_of_Pragma, and the 
equivalent use of No_Dependence, the associated restriction applies to the 
run-time system. 
@dby
If an implementation supports @fa<pragma> Restrictions for a particular 
argument, then except for the restrictions No_Access_Subprograms, 
No_Unchecked_Access, No_Specification_of_Aspect, No_Use_of_Attribute, 
No_Use_of_Pragma, No_Dependence =@> Ada.Unchecked_Conversion, and
No_Dependence =@> Ada.Unchecked_Deallocation, the associated restriction 
applies to the run-time system. 

!ASIS

No ASIS effect.

!ACATS test


!appendix

From: Randy Brukardt
Sent: Thursday, February 14, 2019  8:06 PM

In putting the changes of AI12-0020-1, I happened to notice some old errors:

(1) H.4(24/3) mentions restrictions No_Unchecked_Deallocation and 
No_Unchecked_Conversion. But these were moved to Annex J by AI195-00394-01 in 
favor of a Note (H.4(28/2)). It does mention "equivalent use of No_Dependence", 
but that's more complex than needed.

This paragraph should be replaced by something like:

If an implementation supports pragma Restrictions for a particular argument, 
then except for the restrictions No_Access_Subprograms, No_Unchecked_Access, 
No_Specification_of_Aspect, No_Use_of_Attribute, No_Use_of_Pragma, 
No_Dependence => Ada.Unchecked_Conversion, and No_Dependence => 
Ada.Unchecked_Deallocation, the associated restriction applies to the run-time 
system. 

I suppose one could argue that the old wording allowed the old restrictions 
to be used in the runtime, but that seems irrelevant (the runtime doesn't need 
to be implemented in Ada anyway, so the implementation can do anything that 
gets the right effect). And we generally try not to mention Annex J things 
outside of Annex J.


(2) No_IO gives a list library units that are excluded. I'd suggest that 
Directories be included in this list, since Directories exists mainly to 
support those other units.

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