[Bug fortran/80477] [OOP] Polymorphic function result generates memory leak

["paul.richard.thomas at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80477

--- Comment #11 from paul.richard.thomas at gmail dot com <paul.richard.thomas at gmail dot com> ---
Hi Janus,

I'll take a look tonight. I believe, without the source in front of me, that

s/gfc_add_expr_to_block (&post, gfc_call_free
(tmp));/gfc_add_expr_to_block (&se->post, gfc_call_free (tmp));

Cheers

Paul

On 23 April 2017 at 12:02, janus at gcc dot gnu.org
<gcc-bugzilla@gcc.gnu.org> wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80477
>
> janus at gcc dot gnu.org changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |pault at gcc dot gnu.org
>
> --- Comment #9 from janus at gcc dot gnu.org ---
> Anyway, getting back to the discussion of the actual bug ...
>
> (In reply to janus from comment #4)
>> When changing the function result from CLASS to TYPE, this deallocation
>> seems to be done properly (valgrind shows no leak), and the dump looks like
>> this:
>>
>> [...]
>
> Based on this observation, I cooked up a draft patch that tries to modify the
> code which does the freeing for TYPEs and make it work for CLASSes:
>
>
> Index: gcc/fortran/trans-expr.c
> ===================================================================
> --- gcc/fortran/trans-expr.c    (revision 247083)
> +++ gcc/fortran/trans-expr.c    (working copy)
> @@ -6131,15 +6131,26 @@ gfc_conv_procedure_call (gfc_se * se, gfc_symbol *
>    /* Allocatable scalar function results must be freed and nullified
>       after use. This necessitates the creation of a temporary to
>       hold the result to prevent duplicate calls.  */
> -  if (!byref && sym->ts.type != BT_CHARACTER
> -      && sym->attr.allocatable && !sym->attr.dimension)
> +  if (!byref && sym->ts.type != BT_CHARACTER)
>      {
> -      tmp = gfc_create_var (TREE_TYPE (se->expr), NULL);
> -      gfc_add_modify (&se->pre, tmp, se->expr);
> -      se->expr = tmp;
> -      tmp = gfc_call_free (tmp);
> -      gfc_add_expr_to_block (&post, tmp);
> -      gfc_add_modify (&post, se->expr, build_int_cst (TREE_TYPE (se->expr),
> 0));
> +      if (sym->attr.allocatable && !sym->attr.dimension)
> +       {
> +         tmp = gfc_create_var (TREE_TYPE (se->expr), NULL);
> +         gfc_add_modify (&se->pre, tmp, se->expr);
> +         se->expr = tmp;
> +         gfc_add_expr_to_block (&post, gfc_call_free (tmp));
> +         gfc_add_modify (&post, tmp, build_int_cst (TREE_TYPE (tmp), 0));
> +       }
> +      else if (sym->ts.type == BT_CLASS && CLASS_DATA (sym)->attr.allocatable
> +              && !CLASS_DATA (sym)->attr.dimension)
> +       {
> +         tmp = gfc_create_var (TREE_TYPE (se->expr), NULL);
> +         gfc_add_modify (&se->pre, tmp, se->expr);
> +         se->expr = tmp;
> +         tmp = gfc_class_data_get (tmp);
> +         gfc_add_expr_to_block (&post, gfc_call_free (tmp));
> +         gfc_add_modify (&post, tmp, build_int_cst (TREE_TYPE (tmp), 0));
> +       }
>      }
>
>    /* If we have a pointer function, but we don't want a pointer, e.g.
>
>
> Unfortunately it does not work, because it only creates a copy of the class
> container, but frees up the class data too early:
>
>
> polymorphic_operators_memory_leaks ()
> {
>   static struct a_type_t a = {.x=1.0e+0};
>   static struct a_type_t b = {.x=2.0e+0};
>
>   {
>     struct __class_a_type_m_A_type_t_a D.3528;
>     struct __class_a_type_m_A_type_t_a D.3529;
>
>     D.3528 = add_a_type (&a, &b);
>     D.3529 = D.3528;
>     __builtin_free ((void *) D.3528._data);
>     D.3528._data = 0B;
>     assign_a_type (&a, D.3529._data);
>   }
> }
>
>
> I guess I could use some help here (I always tend to get a bit lost in the
> trans-stage). Paul, do you by chance have any idea how to handle this properly?
>
> --
> You are receiving this mail because:
> You are on the CC list for the bug.