J3/04-336

Date:    10 June 2004
To:      J3
From:    Rob James
Subject: Allocating objects of abstract types

NUMBER:
TITLE: Allocating objects of abstract types
KEYWORDS: ALLOCATE, ABSTRACT
DEFECT TYPE:
STATUS: J3 consideration in progress

QUESTION:

Question 1
----------
Consider the following code:

      module m
        type, abstract :: t
          integer :: i
        end type
        class(t), allocatable :: d
      end module

      program foo
        use m
        allocate(d)
      end

One cannot declare a non-polymorphic object of an abstract type.
Similarly, a polymorphic object should not be allocated with a dynamic
type that is abstract.

A <type-spec> in an allocate statement cannot specify an abstract
type.  But the effect of the allocate statement in the example above
is the same as if a <type-spec> specifying an abstract type appeared
in the allocate statement, which would not be standard-conforming.

Was this example intended to be standard-conforming?


Question 2
----------
Consider the following code:

      module m
        type, abstract :: t
          integer :: i
        end type
        type, extends(t) :: t2
          integer :: j
        end type
        class(t), allocatable :: d
        type(t2) :: d2 = t2(1, 2)
      end module

      program foo
        use m
        allocate(d, source=d2%t)
      end

Similarly to the example in question 1, the allocate statement is
allocating an object of a dynamic type that is abstract.

Was this example intended to be standard-conforming?

ANSWER:
No, neither of these examples were intended to be standard-conforming.
Edits are provided to correct these oversights.

EDITS:
All edits refer to 04-007.
[111:12+] Add the following constraint:
  C625.1 (R623) If any <allocate-object> has a declared type that is
         abstract, either <type-spec> or SOURCE= shall apear.
[111:23+] Add the following constraint:
  C632.1 (R624) The <source-expr> shall not have a dynamic type that
         is abstract.

SUBMITTED BY: Rob James

HISTORY: 04-336   m169 Submitted