[Bug fortran/59015] New: I/O of derived type with private component is forbidden

[Bug fortran/59015] New: I/O of derived type with private component is forbidden

[fxcoudert at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59015

            Bug ID: 59015
           Summary: I/O of derived type with private component is
                    forbidden
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxcoudert at gcc dot gnu.org

We should diagnose and prevent I/O of a derived-type object with one or more
private components. Example:

module foo
  type, public :: t
    private
    integer :: hidden
  end type t

  type(t), parameter, public :: v = t(42)
end module foo

program test
  use foo
  print *, v
end

This currently compiles and print 42. It should be rejected.

[Bug fortran/59015] I/O of PARAMETER derived type with private component is forbidden

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59015

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid, diagnostic
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-11-06
                 CC|                            |burnus at gcc dot gnu.org
            Summary|I/O of derived type with    |I/O of PARAMETER derived
                   |private component is        |type with private component
                   |forbidden                   |is forbidden
     Ever confirmed|0                           |1

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Confirmed. Not even -pedantic -std=f95 has any effect.

Note: The issue only affects PARAMETER. For module variables, one gets:
  Error: Data transfer element at (1) cannot have PRIVATE components


Fortran 2008, "9.6.3 Data transfer input/output list", second bullet point of
paragraph 7 [see last sentence after the ";"]

"If a list item of derived type in an unformatted input/output statement is not
processed by a defined input/output procedure (9.6.4.8), and if any subobject
of that list item would be processed by a defined input/output procedure, the
list item is treated as if all of the components of the object were specified
in the list in component order (4.5.4.7); those components shall be accessible
in the scoping unit containing the input/output statement and shall not be
pointers or allocatable."

[Bug fortran/59015] I/O of PARAMETER derived type with private component is forbidden

[fxcoudert at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59015

--- Comment #2 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
We don't trigger the check in resolve.c:resolve_transfer() because we bail out
early:

  if (exp == NULL || (exp->expr_type != EXPR_VARIABLE
                      && exp->expr_type != EXPR_FUNCTION))
    return;

I'm testing a patch to allow EXPR_STRUCTURE to go through the checks.

[Bug fortran/59015] I/O of PARAMETER derived type with private component is forbidden

[fxcoudert at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59015

--- Comment #3 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> ---
Allowing EXPR_STRUCTURE to go through the tests (by adding it along
EXPR_VARIABLE and EXPR_FUNCTION) leads to a failure of c_ptr_tests_16.f90 (the
rest of the testsuite works ok). The code that triggers it uses a TRANSFER:

module foo
  type mytype
    integer, private :: a, b, c
  end type mytype
end module foo

  use foo
  type(mytype) x
  print *, transfer(32512, x)
end

There is a segfault when it tries to access the symbol of the TRANSFER:

  sym = exp->symtree->n.sym;

I'm not able to dig any further, so I'll let someone else take care of it.