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Subject: [Bug fortran/54958] New: Wrongly rejects ac-implied-DO variables which also occur with INTENT(IN)
Date: Wed, 17 Oct 2012 19:16:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54958

             Bug #: 54958
           Summary: Wrongly rejects ac-implied-DO variables which also
                    occur with INTENT(IN)
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org


gfortran rejects all four uses of "i" in the following program with

  Error: Dummy argument 'i' with INTENT(IN) in variable definition context
         (iterator variable) at (1)

However, it should only reject the use as variable in io-implied-do and in the
do-stmt and not the (ac-,data-)implied-do variable. Cf. IR 000076 at
ftp://ftp.nag.co.uk/sc22wg5/n1351-n1400/N1393.txt

g95, pathf95 and NAG properly handle this case, gfortran 4.1 to 4.8 doesn't.


subroutine test(i)
  integer, intent(in) :: i
  integer :: A(5)
  ! Valid: data-implied-do  [WRONGLY rejected by gfortran]
  DATA (A(i), i=1,5)/5*42/

  ! Valid: ac-implied-do  [WRONGLY rejected by gfortran]
  print *, [(i, i=1,5 )]

  ! Invalid: io-implied-do  [OK: rejected by gfortran]
  print *, (i, i=1,5 )

  ! Invalid: do-variable in a do-stmt  [OK: rejected by gfortran]
  do i = 1, 5
  end do
end




>>From the standard (F2008):

"C539 (R523) A nonpointer object with the INTENT (IN) attribute shall not
appear in a variable definition context (16.6.7)."

and in "16.6.7 Variable definition context":

"(4) a do-variable in a do-stmt or io-implied-do;"


The reason that a data-implied-do and ac-implied-do is allowed is given at
"16.4 Statement and construct entities":

"The name of a data-i-do-variable in a DATA statement or an ac-do-variable in
an array constructor has a scope of its data-implied-do or ac-implied-do. [...]
The appearance of a name as a data-i-do-variable of an implied DO in a DATA
statement or an ac-do-variable in an array constructor is not an implicit
declaration of a variable whose scope is the scoping unit that contains the
statement."