[Bug fortran/48831] New: check.c: Constant expression (PARAMETER array element) rejected as nonconstant

[Bug fortran/48831] New: check.c: Constant expression (PARAMETER array element) rejected as nonconstant

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48831

           Summary: check.c: Constant expression (PARAMETER array element)
                    rejected as nonconstant
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: major
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org
            Blocks: 32834


I know that this PR is a duplicate of some PR which I cannot find.

http://groups.google.com/group/comp.lang.fortran/browse_thread/thread/d0bd8bd1803b626e
has the following program, which is rejected with:


    i3 = int(0, i2(1))  ! This line gives an error when compiling.
                1
Error: 'kind' argument of 'int' intrinsic at (1) must be a constant


In check.c, there is a simple expr_type == EXPR_CONSTANT check; however, using
gfc_is_constant_expr() doesn't work either as PARAMETER (arrays) are not
recognized as being constant. (EXPR_VARIABLE + FL_PARAMETER.)

I think expr.c's check_init_expr might be better (it is currently static);
however, I have the feeling all checks are wrong.

Note: Fortran 95 distinguishes between initialization and constant expressions,
in Fortran 2003 and Fortran 2008 they have been merged to a single type -
called "initialization expressions" in Fortran 2003 and "constant expressions"
in Fortran 2008.

TODO:
- Find out what F90's constant and init expressions mean
- Make the less powerful call the more powerful, except for -std=f95
- Add checks for init/constant following the F95 pattern everywhere instead of
using the half-baked EXPR_CONST or some made up test which check more, but only
locally (e.g. const_expr + const array, as done in simplify.c)


Note: The case below should unaffected by the const/init change and should be
already valid Fortran 95.

program p1
    implicit none
    integer, parameter  :: i1    = kind(0)
    integer, parameter  :: i2(1) = [i1]
    integer(kind=i2(1)) :: i3

    i3 = int(0, i1)
    print *, i3

    i3 = int(0, i2(1))  ! This line gives an error when compiling.
    print *, i3
end program p1

[Bug fortran/48831] check.c: Constant expression (PARAMETER array element) rejected as nonconstant

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48831

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-06-03 13:21:55 UTC ---
Author: burnus
Date: Sun Jun  3 13:21:50 2012
New Revision: 188152

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=188152
Log:
2012-06-03  Alessandro Fanfarillo  <fanfarillo.gcc@gmail.com>
            Tobias Burnus  <burnus@net-b.de>

        PR fortran/48831
        * gfortran.h (gfc_check_init_expr): Add prototype declaration
        of function.
        * check.c (kind_check): Change if condition to use
        to gfc_check_init_expr.
        * expr.c (check_init_expr): Remove forward declaration
        and static keyword. Change name in gfc_check_init_expr.

2012-06-03  Alessandro Fanfarillo  <fanfarillo.gcc@gmail.com>

        PR fortran/48831
        * gfortran.dg/parameter_array_element_2.f90: New.


Added:
    trunk/gcc/testsuite/gfortran.dg/parameter_array_element_2.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/check.c
    trunk/gcc/fortran/expr.c
    trunk/gcc/fortran/gfortran.h
    trunk/gcc/testsuite/ChangeLog

[Bug fortran/48831] check.c: Constant expression (PARAMETER array element) rejected as nonconstant

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48831

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |burnus at gcc dot gnu.org
         Resolution|                            |FIXED

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-06-03 13:29:36 UTC ---
FIXED on the trunk (4.8).

Thanks Alessandro for the patch!