On 01/14/2015 08:47 AM, Mark Wielaard wrote:
On Wed, 2015-01-14 at 09:26 -0500, Jason P. Leasure wrote:
> The type_offset of a type unit header is relative to the beginning
> of the type unit header.
>
> Signed-off-by: Jason P. Leasure <jpleasu(a)super.org>
> ---
> libdw/dwarf_formref_die.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libdw/dwarf_formref_die.c b/libdw/dwarf_formref_die.c
> index 63f6697..8b92e22 100644
> --- a/libdw/dwarf_formref_die.c
> +++ b/libdw/dwarf_formref_die.c
> @@ -95,7 +95,7 @@ dwarf_formref_die (attr, result)
>
> datap = cu->dbg->sectiondata[IDX_debug_types]->d_buf;
> size = cu->dbg->sectiondata[IDX_debug_types]->d_size;
> - offset = cu->type_offset;
> + offset = cu->start + cu->type_offset;
Thanks, I believe this is correct. I am surprised we didn't encounter
this earlier. Do you happen to have a testcase for it?
It's a regression from commit 9202665816763, before which cu->start was
used with the offset everywhere.
I can see this in my dwarvish tool with Jason's example source. You
just need a ref_sig8 that's not in the first type_unit, cu->start > 0.
So here, struct A has a ref_sig8 to struct B in the second type_unit.
In the bad case I see "signature ref_sig8 [30] 0", where those last
two bits are supposed to be the offset and tag.
I see "signature ref_sig8 [72] structure_type" with 0.160, or with
master and this patch, and it expands the tree of attributes from there.
Of course you won't want a GUI for tests, but it should be easy to craft
this one directly.