http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51380
Bug #: 51380
Summary: ASSIGNMENT(=): Reject ALLOCATABLE/POINTER dummy
argument
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Keywords: accepts-invalid, diagnostic
Severity: normal
Priority: P3
Component: fortran
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: bur...@gcc.gnu.org
The following program is invalid as the call to the assignment function should
act as if the "from" argument is enclosed in parentheses. That directly implies
that the actual argument cannot be allocatable or a pointer.
For the topic and the standard, cf.
http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/13ac0c0e52339468
Note: Strictly speaking, only the call to the function is invalid while the
declaration is valid (but may not be used).
>From the standard (F2003, found by Richard Maine):
"A defined assignment is treated as a reference to the subroutine,
with the left-hand side as the first argument and the right-hand-side
enclosed in parentheses as the second argument." (12.3.2.1.2, paragraph 2)
Possibilities:
* Error for the usage
* Error for the declaration (even if valid, it may not be used)
* Warning for the declaration, error for using it
The following program is compiled without any error/(default) warning in
gfortran.
While the IBM compiler prints the error (as stated in c.l.f):
(S) Dummy argument sets of procedure or binding assign_set_i4_2_pv must
not be specified with the ALLOCATABLE attribute. assign_set_i4_2_pv
will not be included in the ASSIGNMENT(=) generic interface.
module m
type t1
integer :: i
end type t1
type t2
real :: r
end type t2
interface assignment(=)
module procedure assign1
module procedure assign2
end interface
contains
subroutine assign1 (a, b)
type(t1), intent(out) :: a
type(t1), intent(in), ALLOCATABLE :: b ! valid but questionable
a%i = b%i
end subroutine assign1
subroutine assign2 (a, b)
type(t2), intent(out) :: a
type(t2), intent(in), POINTER :: b ! valid but questionable
a%r = b%r
end subroutine assign2
end module m
use m
type(t1), allocatable :: x1
type(t2), pointer :: x2
allocate(x1, x2)
x1 = x1 ! << Invalid, equivalent to: call assign1(x1, (x1))
! and (x1) is not allocatable
x1 = (x1) ! << Similarly invalid, but with explicit (.)
x2 = x2 ! << Invalid, equivalent to: call assign2(x1, (x1))
! and (x2) is not a pointer
x2 = (x2) ! << Similarly invalid, but with explicit (.)
end
