(j3.2006) deallocating pointer function results

[Robert Corbett]

On 11/03/15 13:44, Van Snyder wrote:
> On Tue, 2015-11-03 at 02:34 -0800, Robert Corbett wrote:
>> >  The following message is based on a thread on comp.lang.fortran.
>> >  All references are with respect to Fortran 2008.
>> >  
>> >  Consider the following program:
>> >  
>> >  !-----------------------------------------------------------------
>> >  
>> >  program main
>> >  
>> >       deallocate( new_int() )              ! (1)
>> >       call my_deallocate( new_int() )      ! (2)
>> >       call hmm_deallocate( new_int() )     ! (3)
>> >  
>> >  contains
>> >       function new_int()
>> >         integer, pointer :: new_int
>> >         allocate(new_int)
>> >         new_int = 3
>> >       end function
>> >  
>> >       subroutine my_deallocate(p)
>> >         integer, pointer  :: p
>> >         deallocate( p )
>> >       end subroutine
>> >  
>> >       subroutine hmm_deallocate(p)
>> >         integer, pointer  :: p, q
>> >         q =>  p
>> >         deallocate( q )
>> >       end subroutine
>> >  end
>> >  
>> >  !-----------------------------------------------------------------
>> >  The statement marked (2) leads to prohibited behavior.
>> >  Subclause 5.3.10, paragraph 5, states
>> >  
>> >          If no INTENT attribute is specified for a dummy argument,
>> >          its use is subject to the limitations of its effective
>> >          argument (12.5.2).
>> >  
>> >  Because a function reference is not allowed as an
>> >  /allocate-object/  in a DEALLOCATE statement, a dummy argument
>> >  corresponding to an actual argument that is a function reference
>> deallocate statement.  Argument association is not textual substitution.

The quoted restriction is the restriction that prohibits changing the
value of a dummy variable that is associated with an actual argument
that is not a variable.  The program

       PROGRAM MAIN
         CALL SUBR(FUNC())
       CONTAINS
         FUNCTION FUNC()
           FUNC = 1.0
         END FUNCTION
         SUBROUTINE SUBR(X)
           X = 2.0
           PRINT *, X
         END SUBROUTINE
       END

is not standard conforming because it violates that restriction.  The
program that deallocates the pointer dummy variable violates the same
restriction, but for a pointer dummy variable instead of an ordinary
dummy variable.

Robert Corbett
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