[Patch, fortran] PR51976 - [F2003] Support deferred-length character components of derived types (allocatable string length)

[Paul Richard Thomas <paul dot richard dot thomas at gmail dot com>]

Dear All,

The attached patch represents progress to date.  It fixes the original
problem in this PR and allows John Reid's version of
iso_varying_string/vocabulary_word_count.f90 to compile and run
correctly.  It even bootstraps and regtests!

However, it doe not fix:
PR51976 comment #6 and PR51550 - allocate with typespec ICEs
PR51976 comment #6 FORALL assignment is messed up and ICEs..
PR47545 the compiler complains about the lack of an initializer for
the hidden character length field.
PR45170 will need going through from one end to the other - there is a
lot of "stuff" here!

Of these, I consider the fix of the PR47545 problem to be a must and
the allocate with typespec desirable.

Cheers

Paul

2013-02-24  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/51976
    * gfortran.h : Add deferred_parameter attribute.
    * primary.c (build_actual_constructor): It is not an error if
    a missing component has the deferred_parameter attribute;
    equally, if one is given a value, it is an error.
    * resolve.c (resolve_fl_derived0): Remove error for deferred
    character length components.  Add the hidden string length
    field to the structure. Give it the deferred_parameter
    attribute.
    * trans-array.c (duplicate_allocatable): Add a strlen field
    which is used as the element size if it is non-null.
    (gfc_duplicate_allocatable, gfc_copy_allocatable_data): Pass a
    NULL to the new argument in duplicate_allocatable.
    (structure_alloc_comps): Set the hidden string length as
    appropriate. Use it in calls to duplicate_allocatable.
    (gfc_alloc_allocatable_for_assignment): When a deferred length
    backend declaration is variable, use that; otherwise use the
    string length from the expression evaluation.
    * trans-expr.c (gfc_conv_component_ref): If this is a deferred
    character length component, the string length should have the
    value of the hidden string length field.
    (gfc_trans_subcomponent_assign): Set the hidden string length
    field for deferred character length components.  Allocate the
    necessary memory for the string.
    (alloc_scalar_allocatable_for_assignment): Same change as in
    gfc_alloc_allocatable_for_assignment above.
    * trans-stmt.c (gfc_trans_allocate): Likewise.
    * trans-types.c (gfc_get_derived_type): Set the tree type for
    a deferred character length component.
    * trans.c (gfc_deferred_strlen): New function.
    * trans.h : Prototype for the new function.

2013-02-24  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/51976
    * gfortran.dg/deferred_type_component_1.f90 : New test.

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