Re: [PATCH] Don't handle blocks as exprlocs for DWARF version 4 or higher.

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Feb 18, 2021 at 05:59:40PM +0100, Jakub Jelinek via Dwz wrote:
> Anyway, looking around some more,
>               if (unlikely (low_mem_phase1)
>                   && add_locexpr_dummy_dies (dso, cu, die, ptr, form,
>                                              t->attr[i].attr, len))
>                   goto fail;
> looks incorrect to me, form in that case will be DW_FORM_block{2,4,}
> and won't be canonicalized to DW_FORM_block1.  And furthermore
> len will be always 0.  It is preceded only by
>               size_t len = 0;
> and a loop handling DW_FORM_indirect.  So, ptr will always be
> the pointer to the block count too.

Another possibility would be (if we don't want to slow down non-low mem
case) to just repeat that
> 	      switch (form)
> 		{
> 		case DW_FORM_block1:
> 		  len = *ptr++;
> 		  break;
> 		case DW_FORM_block2:
> 		  len = read_16 (ptr);
> 		  form = DW_FORM_block1;
> 		  break;
> 		case DW_FORM_block4:
> 		  len = read_32 (ptr);
> 		  form = DW_FORM_block1;
> 		  break;
> 		case DW_FORM_block:
> 		  len = read_uleb128 (ptr);
> 		  form = DW_FORM_block1;
> 		  break;
> 		case DW_FORM_exprloc:
> 		  len = read_uleb128 (ptr);
> 		  break;
> 		default:
> 		  break;
> 		}
at the start of add_locexpr_dummy_dies (and not pass len to that function
and have it instead as a local var.  Perhaps even by doing:
  size_t len = 0;
  if (cu->cu_version < 4)
    {
      switch (form)
	{
	... // the above switch without DW_FORM_exprloc in there
	}
      if (form == DW_FORM_block1)
	...
    }

  if (form == DW_FORM_exprloc)
    {
      len = read_uleb128 (ptr);
      return read_exprloc_low_mem_phase1 (dso, die, ptr, len);
    }

...

	Jakub