To: J3                                                     J3/26-219
From: Malcolm Cohen
Subject: Interp F23/028 on NOTIFY_TYPE pointers
Date: 2026-October-23


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NUMBER: F23/029
TITLE: Can a variable of type NOTIFY_TYPE be a pointer?
KEYWORDS: NOTIFY_TYPE, POINTER
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress
REFERENCES: 24-007

QUESTION:

A named variable of type NOTIFY_TYPE cannot be a pointer, as it is
required to be a coarray (C854 says pointers cannot be coarrays).

However, a component of type NOTIFY_TYPE is apparently permitted to be
a pointer. This is problematic, as in:

    TYPE t
        TYPE(notify_type),POINTER :: p
    END TYPE
    TYPE(t) x[*]
    REAL y[*]

    ... assume that x%p becomes associated on the executing image,
    ... whether by allocation or pointer assignment

    y[n,NOTIFY=x%p] = 999

The assignment statement
   "increments the count of the corresponding notify variable on the
    image specified by the image selector"

But there is no corresponding notify variable, because x%p is not a
subobject of X, and therefore is not a coarray. That renders any use
of x%p for synchronisation non-conforming.

And that renders NOTIFY_TYPE pointer components useless, quite apart
from the inconsistency with not allowing them for named variables of
type NOTIFY_TYPE.

Should components of type NOTIFY_TYPE be required to be nonpointer?

ANSWER:

Yes, such components should not be pointers.

An edit is supplied to correct this oversight.

EDIT to 24-007.

[462:14] 16.10.2.22 NOTIFY_TYPE, C1612 "A named entity...",
         before "data component"
         insert "nonpointer".
That makes the whole constraint read:
   "C1612 A named entity with declared type NOTIFY_TYPE, or which has
          a noncoarray potential subobject component with declared
          type NOTIFY_TYPE, shall be a variable. A component that is
          of such a type shall be a nonpointer data component."

SUBMITTED BY: Malcolm Cohen

HISTORY: 26-nnn   m241  Submitted

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