To: J3                                                     J3/23-243r1
From: Malcolm Cohen
Subject: Interp: Coarray correspondence in DEALLOCATE
Date: 2023-October-26
References: 23-169, 23-218

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NUMBER: F23/012
TITLE: Coarray correspondence in DEALLOCATE
KEYWORDS: DEALLOCATE, coarray
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

In 9.7.3.2 Deallocation of allocatable variables, paragraph 11
requires that coarray dummy arguments on the active images have
ultimate arguments that are corresponding coarrays.

However, there appears to be no such requirement for coarray
components of dummy arguments.

Thus this program appears to be valid (apart from having no
interpretation due to coarray allocation status inconsistency):

    Program trouble
        Type t
            Real,Allocatable :: c(:)[:]
        End Type
        Type(t) x,y
        Allocate(x(1)[*],y(1)[*])
        If (This_Image()==1) Then
            Call oops(x)
        Else
            Call oops(y)
        End If
        Print *,Allocated(x%c),Allocated(y%c)
        Sync All
    Contains
        Subroutine oops(z)
            Type(t) :: z
            Deallocate(z%c)
        End Subroutine
    End Program

Should there be a requirement on coarray components of dummy arguments
in DEALLOCATE?

There is also an editorial glitch in paragraph 10 where it says that a
coarray does not "become deallocated on an image unless it is
successfully deallocated on all active images", since "it" exists on
only one image (the others being the corresponding coarrays), and "all
active images" includes the image in question, so is circular. Should
this not be corrected?

ANSWER:

Yes, this requirement should be explicit.

Yes, the wording in the last sentence of paragraph 10 is poor, and
should be improved.

Edits are supplied to address these defects.

As the question noted, the example is not conforming as it violates
the semantics that corresponding coarrays have the same allocation
status, bounds, etc. on all images on which they are established.

EDIT to N2218:

[152] 9.7.3.2 Deallocation of allocatable variables, paragraph 10,
      last sentence,
      change "it is" to "the corresponding coarrays are",
      and insert "other" between "all" and "active",
      making that whole sentence read:
    "A coarray shall not become deallocated on an image unless the
     corresponding coarrays are successfully deallocated on all other
     active images in this team."
{Clarify "it" and "all".}

[152] Same subclause, paragraph 11 beginning "If an allocate-object is
      a coarray dummy argument", append new sentence
    "If an allocate-object is a coarray subcomponent of a dummy
     argument, those components of the ultimate arguments on those
     images shall be corresponding coarrays."
{Requirement needed to maintain coarray correspondence semantics.
 A "subcomponent" is a component that is an immediate component,
 of a component of a subobject.}

SUBMITTED BY: John Reid & Reinhold Bader

HISTORY: 23-218   m231  Submitted
         23-nnn   m231  Revised

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