PR fortran/93524 - rank >= 3 array stride incorrectly set in CFI_establish

[Harris Snyder]

Hi all,

Now that my copyright assignment is complete, I'm submitting this fix.
Test cases are included.
OK for master? I do not have write access, so someone will need to
commit this for me.

Regards,
Harris

libgfortran/ChangeLog:

    * runtime/ISO_Fortran_binding.c (CFI_establish):  fixed strides
for rank >2 arrays

gcc/testsuite/ChangeLog:

    * gfortran.dg/ISO_Fortran_binding_18.c: New test.
    * gfortran.dg/ISO_Fortran_binding_18.f90: New test.




On Wed, Jan 13, 2021 at 2:10 PM Harris Snyder <hsnyder@structura.bio> wrote:
>
> Hi Tobias / all,
>
> Further related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93524
> `sm` is being incorrectly computed in CFI_establish. Take a look at
> the diff below - we are currently only using the extent of the
> previous rank to assign `sm`, instead of all previous ranks. Have I
> got this right, or am I missing something / does this need to be
> handled differently? I can offer some test cases and submit a proper
> patch if we think this solution is OK...
>
> Thanks,
> Harris
>
> diff --git a/libgfortran/runtime/ISO_Fortran_binding.c
> b/libgfortran/runtime/ISO_Fortran_binding.c
> index 3746ec1c681..20833ad2025 100644
> --- a/libgfortran/runtime/ISO_Fortran_binding.c
> +++ b/libgfortran/runtime/ISO_Fortran_binding.c
> @@ -391,7 +391,12 @@ int CFI_establish (CFI_cdesc_t *dv, void
> *base_addr, CFI_attribute_t attribute,
>           if (i == 0)
>             dv->dim[i].sm = dv->elem_len;
>           else
> -           dv->dim[i].sm = (CFI_index_t)(dv->elem_len * extents[i - 1]);
> +           {
> +             CFI_index_t extents_product = 1;
> +             for (int j = 0; j < i; j++)
> +               extents_product *= extents[j];
> +             dv->dim[i].sm = (CFI_index_t)(dv->elem_len * extents_product);
> +           }
>         }
>      }
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