To: J3                                                        11-201r1
From: Van Snyder / Tobias Burnus
Subject: Mixing default initialization with DATA initialization
Date: 2011 June 28
References: WG5/N1830


----------------------------------------------------------------------

NUMBER: F08/0062
TITLE: Mixing default initialization with DATA initialization
KEYWORDS: DATA, default initialization, explicit initalization
DEFECT TYPE: Clarification
STATUS: J3 consideration in progress

QUESTION:

In the following program, one component has a default initialization
and the other is initialized in a DATA statement. Is the program
valid?

  module oad_active
    implicit none
    type active
      integer :: v
      integer :: d = 42
    end type
  end module

  module tots_c
    use oad_active
    implicit none
    type(active), save :: trlkold
    data trlkold%v /100/
  end module

  program foo
    use tots_c
    implicit none
    if (trlkold%d /=  42) stop 'ERROR d /= 42'
    if (trlkold%v /= 100) stop 'ERROR v /= 100'
  end program foo


WG5/N1830 has [p104, 5.4.7, parag. 2]

  If a nonpointer object has default initialization, it shall not
  appear in a <data-stmt-object-list>.

and [p89, 5.2.3, parag. 1]

  Explicit initialization alternatively may be specified in a DATA
  statement unless the variable is of a derived type for which default
  initialization is specified. [...] A variable, or part of a
  variable, shall not be explicitly initialized more than once in a
  program.

and [p70, 4.5.4.6, parag. 6]

  Explicit initialization in a type declaration statement (5.2)
  overrides default initialization


ANSWER:

It was intended that the data statement not be conforming.

5.4.7p2 was carefully worded to use "shall not appear" rather than
"shall not be the <data-stmt-object>".

The intention was that an object be initialized entirely in a type
declaration statement, or that only those parts of it having default
initialization be initialized.  It was considered to be a burden on
processors to be required to initialize some parts of a structure
using default initialization, and other parts of it explicitly.

EDITS:

None.

SUBMITTED BY: Tobias Burnus

HISTORY: 11-201    m195  Submitted
         11-201r1        Draft answer.

----------------------------------------------------------------------