To: J3                                                     J3/23-220r1
From: John Reid & Reinhold Bader && Malcolm Cohen
Subject: Interp for MOVE_ALLOC with FROM a coarray
Date: 2023-October-16

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NUMBER: F23/010
TITLE: MOVE_ALLOC with coarray arguments
KEYWORDS: MOVE_ALLOC, coarray
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

If the FROM and TO arguments to MOVE_ALLOC are coarrays, are
corresponding invocations of MOVE_ALLOC required to have their FROM
(and TO) arguments be corresponding coarrays?

For example, this program ends up with A and B not having the same
allocation status on all images, which surely cannot be right.

    program trouble
      real, allocatable :: a[:], b[:]
      allocate(a[*],b[*])
      if (this_image()>1) then
        call sub(a,b)
        ! Now, A is deallocated and B is allocated
      else
        call sub(b,a)
        ! Now, B is deallocated and A is allocated
      end if
    contains
      subroutine sub(s,t)
        real, allocatable :: s[:], t[:]
        call move_alloc(s,t)
      end subroutine
    end program

ANSWER:

Yes, those arguments are required to be corresponding coarrays.
An edit is supplied to correct this error.

EDIT to N2218 (Fortran 2023 FDIS):

[423] In 16.9.147 MOVE_ALLOC, Arguments paragraph,
      At the end of the FROM argument description append
        "If it is a coarray, it shall correspond to the FROM arguments
         in all corresponding invocations of MOVE_ALLOC."
      At the end of the TO argument description append
        "If it is a coarray, it shall correspond to the TO arguments
         in all corresponding invocations of MOVE_ALLOC."

SUBMITTED BY: John Reid & Reinhold Bader

HISTORY: 23-170   m230  Submitted
         23-220   m231  Revised
         23-220r1 m231  Revised

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