J3/15-211
To: J3
From: Malcolm Cohen
Subject: Interp on INTENT(OUT) pure polymorphic components
Date: 2015 August 06


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NUMBER: F08/0143
TITLE: May a pure procedure have an INTENT(OUT) polymorphic component?
KEYWORDS: PURE, INTENT(OUT), polymorphic
DEFECT TYPE: Erratum
STATUS: J3 consideration in progress

QUESTION:

Consider:

  Type t
    Class(*),Allocatable :: c
  End Type
  ...
  Pure Subroutine zap(x)
    Type(t),Intent(Out) x
    x%c = 'I wonder if that invoked an impure procedure?'
  End Subroutine

Is this program standard-conforming?

ANSWER:

No, this is not standard-conforming.

Corrigendum 1 of Fortran 2008 added the constraint
  "C1284a A statement that might result in the deallocation of a
          polymorphic entity is not permitted in a pure procedure."

The type declaration statement with INTENT(OUT) causes the
deallocation of the polymorphic component X%C, and is therefore not
allowed.

However, this is difficult to understand, so a clarifying edit is
provided.

EDITS:

In the constraint added by Corrigendum 1,
  "C1278a An INTENT (OUT) dummy argument of a pure procedure shall not
          be polymorphic."

after the word "polymorphic"
insert "or have a polymorphic allocatable ultimate component".

SUBMITTED BY: Malcolm Cohen

HISTORY: 15-nnn    m207  F08/0143  Submitted

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