Re: [PATCH, v2] Fortran: fix for absent array argument passed to optional dummy [PR101135]

[Mikael Morin <morin-mikael@orange.fr>]

Le 15/03/2024 à 20:32, Harald Anlauf a écrit :
> Dear all,
> 
> as there has been some good progress in the handling of optional dummy
> arguments, I looked again at this PR and a patch for it that I withdrew
> as it turned out incomplete.
> 
> It turned out that it now needs only a minor adjustment for optional
> dummy arguments of procedures with bind(c) attribute so that ubsan
> checking does not trigger.
> 
> Along this way I extended the previous testcase to exercise to some
> extent combinations of bind(c) and non-bind(c) procedures and found
> one failure (since at least gcc-9) that is genuine: passing a missing
> optional from a bind(c) procedure to an assumed-rank dummy, see
> PR114355.  The corresponding test is commented in the testcase.
> 
> Regtested on x86_64-pc-linux-gnu.  OK for mainline?
> 
> Thanks,
> Harald
> 
(...)
> 
> From b3079a82a220477704f8156207239e4af4103ea9 Mon Sep 17 00:00:00 2001
> From: Harald Anlauf <anlauf@gmx.de>
> Date: Fri, 15 Mar 2024 20:14:07 +0100
> Subject: [PATCH] Fortran: fix for absent array argument passed to optional
>  dummy [PR101135]
> 
> gcc/fortran/ChangeLog:
> 
> 	PR fortran/101135
> 	* trans-array.cc (gfc_get_dataptr_offset): Check for optional
> 	arguments being present before dereferencing data pointer.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR fortran/101135
> 	* gfortran.dg/missing_optional_dummy_6a.f90: Adjust diagnostic pattern.
> 	* gfortran.dg/ubsan/missing_optional_dummy_8.f90: New test.
> ---
>  gcc/fortran/trans-array.cc                    |  11 ++
>  .../gfortran.dg/missing_optional_dummy_6a.f90 |   2 +-
>  .../ubsan/missing_optional_dummy_8.f90        | 108 ++++++++++++++++++
>  3 files changed, 120 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gfortran.dg/ubsan/missing_optional_dummy_8.f90
> 
> diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
> index 3673fa40720..a7717a8107e 100644
> --- a/gcc/fortran/trans-array.cc
> +++ b/gcc/fortran/trans-array.cc
> @@ -7526,6 +7526,17 @@ gfc_get_dataptr_offset (stmtblock_t *block, tree parm, tree desc, tree offset,
>  
>    /* Set the target data pointer.  */
>    offset = gfc_build_addr_expr (gfc_array_dataptr_type (desc), tmp);
> +
> +  /* Check for optional dummy argument being present.  Arguments of BIND(C)
> +     procedures are excepted here since they are handled differently.  */
> +  if (expr->expr_type == EXPR_VARIABLE
> +      && expr->symtree->n.sym->attr.dummy
> +      && expr->symtree->n.sym->attr.optional
> +      && !is_CFI_desc (NULL, expr))

I think the condition could additionally check the lack of subreferences.
But it's maybe not worth the trouble, and the patch is conservatively 
correct as is, so OK.

Thanks for the patch.

> +    offset = build3_loc (input_location, COND_EXPR, TREE_TYPE (offset),
> +			 gfc_conv_expr_present (expr->symtree->n.sym), offset,
> +			 fold_convert (TREE_TYPE (offset), gfc_index_zero_node));
> +
>    gfc_conv_descriptor_data_set (block, parm, offset);
>  }
>