Re: [PATCH, PR 57748] Check for out of bounds access, Part 2

[Richard Biener <richard dot guenther at gmail dot com>]

On Thu, Oct 24, 2013 at 2:55 PM, Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
> On Thu, 24 Oct 2013 12:18:43, Richard Biener wrote:
>>
>> On Thu, Oct 24, 2013 at 10:48 AM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>>>> I think that is common practice to write array[1]; at the end of the
>>>> structure, and use it as a flexible array. The compute_record_mode has no
>>>> way to decide if that is going to be a flexible array or not.
>>>>
>>>> Sorry Eric, but now I have no other choice than to go back to my previous
>>>> version of part 2:
>>>>
>>>> http://gcc.gnu.org/ml/gcc-patches/2013-10/msg00222.html
>>>
>>> Why? Just set BLKmode in this case as well.
>>
>> Works for me if it works ABI-wise (which you say it should unless the
>> backend is buggy). Note that means mode_for_array should unconditionally
>> return BLKmode.
>
> Did you just propose:
>
> --- stor-layout.c.orig    2013-10-22 10:46:49.233261818 +0200
> +++ stor-layout.c    2013-10-24 14:54:00.425259062 +0200
> @@ -471,27 +471,7 @@
>  static enum machine_mode
>  mode_for_array (tree elem_type, tree size)
>  {
> -  tree elem_size;
> -  unsigned HOST_WIDE_INT int_size, int_elem_size;
> -  bool limit_p;
> -
> -  /* One-element arrays get the component type's mode.  */
> -  elem_size = TYPE_SIZE (elem_type);
> -  if (simple_cst_equal (size, elem_size))
> -    return TYPE_MODE (elem_type);
> -
> -  limit_p = true;
> -  if (host_integerp (size, 1) && host_integerp (elem_size, 1))
> -    {
> -      int_size = tree_low_cst (size, 1);
> -      int_elem_size = tree_low_cst (elem_size, 1);
> -      if (int_elem_size> 0
> -      && int_size % int_elem_size == 0
> -      && targetm.array_mode_supported_p (TYPE_MODE (elem_type),
> -                         int_size / int_elem_size))
> -    limit_p = false;
> -    }
> -  return mode_for_size_tree (size, MODE_INT, limit_p);
> +  return BLKmode;
>  }
>
> ???

Yes.  Does it work?

Richard.

>
>> Richard.
>>
>>> --
>>> Eric Botcazou