[Bug fortran/39988] New: F2008: Default initialization, structure constructors, and allocatable components

["w6ws at earthlink dot net" <gcc-bugzilla at gcc dot gnu dot org>]

Consider the following test case:

program defallocatable
  implicit none

! Demonstrate structure constructors with default initialization
! and allocatable arrays.  (Unspecified in F2003, initialized to
! unallocated in F2008.)

  type mytype_t
    integer, allocatable :: data(:)
  end type

  type(mytype_t) :: my_object

  my_object = mytype_t ()
  print *, 'allocated =', allocated (my_object%data)

end program

When compiling with gfortran, we get:

$ gfortran defallocatable.f90
defallocatable.f90:14.25:

  my_object = mytype_t ()
                        1
Error: No initializer for component 'data' given in the structure constructor
at (1)!
$

This may be a valid error in F2003.  In F2003 section 4.5.9 paragraph 3, it
states that "If a component with default initialization has no corresponding
component-data-source, then the default initialization is applied to that
component."  But when a component is allocatable, it is not legal to specify
a component-data-source.  This creates a difference in how default
initialization
works with structure constructors, and other places where default
initialization
must take place.

In F2008 the above paragraph, this time in section 4.5.10 paragraph 3, adds:
"If an allocatable component has no corresponding component-data-source,
then that component has an allocation status of unallocated."  This closes
the hole and makes default initialization of allocatable components in
structure constructors work like it does everywhere else.

So this enhancement request is to consider gfortran allow the code to compile
under the F2008 semantics (which are seemingly undefined in F2003.)

FWIW, g95 and ifort have the same problem.


-- 
           Summary: F2008: Default initialization, structure constructors,
                    and allocatable components
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: w6ws at earthlink dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39988