To: J3                                                     10-210
From: R. Bader
Subject: constraints on entities of type LOCK_TYPE
Date: 2010 September 22
Reference: N1814

NUMBER: F08/xxxx
TITLE:  constraints on entities of type LOCK_TYPE
KEYWORDS: locks, polymorphism
DEFECT TYPE: Request for interpretation
STATUS: J3 consideration in progress


Consider the following type definition

  type :: m
    class(*), allocatable :: lock
  end type

  type(m) :: om[*]
  allocate(lock_type :: om%lock)

  and later call a subprogram with a
  type(m), intent(out) :: om[*]
  dummy argument, possibly further down the call stack.

QUESTION:

  Is such a call standard conforming?

DISCUSSION:

  According to constraint C1304, such a call is not allowed; the dummy
  object is required to have INTENT(INOUT). However, it appears that
  it may not be possible to check this at compile time. A similar issue
  may arise for C1303.

  The most appropriate solution may be to prohibit unlimited polymorphic
  entities to be allocated to an entity of type LOCK_TYPE.

SUGGESTED EDIT:

  p399, add constraint

  C1302a An unlimited polymorphic entity shall not be of dynamic type
         LOCK_TYPE or one of its extensions


SUBMITTED BY: R. Bader

HISTORY: Submitted September 22, 2010