Dear All,

I ran into Ian Chivers in last week's BCS meeting, who told me that he
had found a PDT bug. My response was to post it on Bugzilla, which he
did.... promptly :-) So promptly, in fact, that I felt honour bound to
respond in kind.

Please find attached a patch to fix his bug and the extension to
recursive allocatable instead of pointer components. The third
testcase checks some tidying up in trans-array.c to stop valgrind
complaining about jumps on uninitialized variables.

It turns out that the earlier PDT tests that had PDT components in
module declarations all made use of the default parameter expressions.
Ian's bug exposed this and required the handiwork in module.c. This is
straightforward and involves the hijacking of actual_arglist service
functions as elsewhere in the initial PDT patch.

Once recursive allocatable PDT components are added, the compiler
tries to generate vtables and the associated procedures for the
template types. This of course yields nonsense and so
gfc_find_derived_vtab simply returns null.

The rest of the patch is adequately explained apart from the seemingly
trivial change in trans-decl.c. This problem was characterised by
double freeing of a PDT type, as it goes out of scope, in the
'finally' block. Clearly somebody is using 'tmp' uninitialized but I
am blowed if I can find the culprit. I have fixed it by setting it to
NULL_TREE after the intended use. This is not very satisfactory since
there is clearly a buglet lurking in the woods somewhere. My first
thought was that, since this seems to be PDT related, it must be
associated with the earlier PDT chunks. They all look to be clean,
however. I have commented accordingly.

Bootstraps and regtests on FC23/x86_64 - OK for trunk?

Now to turn to Reinhold Bader's really nasty PDT bug....

Cheers

Paul

2017-10-07  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/82375
    * class.c (gfc_find_derived_vtab): Return NULL for a passed
    pdt template to prevent bad procedures from being written.
    * decl.c (gfc_get_pdt_instance): Do not use the default
    initializer for pointer and allocatable pdt type components. If
    the component is allocatbale, set the 'alloc_comp' attribute of
    'instance'.
    * module.c : Add a prototype for 'mio_actual_arglist'. Add a
    boolean argument 'pdt'.
    (mio_component): Call it for the parameter list of pdt type
    components with 'pdt' set to true.
    (mio_actual_arg): Add the boolean 'pdt' and, if it is set, call
    mio_integer for the 'spec_type'.
    (mio_actual_arglist): Add the boolean 'pdt' and use it in the
    call to mio_actual_arg.
    (mio_expr, mio_omp_udr_expr): Call mio_actual_arglist with
    'pdt' set false.
    * resolve.c (get_pdt_spec_expr): Add the parameter name to the
    KIND parameter error.
    (get_pdt_constructor): Check that cons->expr is non-null.
    * trans-array.c (structure_alloc_comps): For deallocation of
    allocatable components, ensure that parameterized components
    are deallocated first. Likewise, when parameterized components
    are allocated, nullify allocatable components first. Do not
    recurse into pointer or allocatable pdt components while
    allocating or deallocating parameterized components. Test that
    parameterized arrays or strings are allocated before freeing
    them.
    (gfc_trans_pointer_assignment): Call the new function. Tidy up
    a minor whitespace issue.
    trans-decl.c (gfc_trans_deferred_vars): Set 'tmp' to NULL_TREE
    to prevent the expression from being used a second time.

2017-10-07  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/82375
    * gfortran.dg/pdt_13.f03 : New test.
    * gfortran.dg/pdt_14.f03 : New test.
    * gfortran.dg/pdt_15.f03 : New test.


-- 
"If you can't explain it simply, you don't understand it well enough"
- Albert Einstein