Hello Stefan,
On Mon, 06 Aug 2012 09:39:53 +0200
Stefan Bader <stefan.bader at canonical.com> wrote:
> On 06.08.2012 07:54, Atsushi Kumagai wrote:
> > Hello Stefan,
> >
> > On Thu, 02 Aug 2012 10:23:13 +0200
> > Stefan Bader <stefan.bader at canonical.com> wrote:
> >
> >>> static void
> >>> adjust_member_offset(Dwarf_Die *die)
> >>> {
> >>> long offset;
> >>>
> >>> if (dwarf_info.member_offset == NOT_FOUND_STRUCTURE) // this comparison is always true
> >>> return;
> >>> if (!get_data_member_location(die, &offset))
> >>> return;
> >>> dwarf_info.member_offset += offset;
> >>> }
> >>>
> >>> At least, the change below works fine without regression.
> >>>
> >>>
> >>> diff --git a/dwarf_info.c b/dwarf_info.c
> >>> index 583df53..03e4c90 100644
> >>> --- a/dwarf_info.c
> >>> +++ b/dwarf_info.c
> >>> @@ -520,7 +520,9 @@ search_member(Dwarf_Die *die)
> >>> /*
> >>> * Get the member offset.
> >>> */
> >>> - if (!get_data_member_location(walker, &offset))
> >>> + if (dwarf_tag(die) == DW_TAG_union_type)
> >>
> >> Hm, should that not be die_type to check what the walker is on? And in that case
> >> it seems that check was made just before... So maybe it would be ok to assume 0
> >> as the offset when getting here...?
> >
> > As you said, the walker will be a member of union or struct when reaching here,
> > because is_anonymous_container() already checked the walker.
> >
> > However, get_data_member_location() must succeed if the walker is a member of struct
> > while it doesn't succeed if the walker is a member of union.
> > That's why I added the code to check whether the walker is a member of union or not.
>
> Right, I was just wondering whether that would allow to simplify even more. Like
> this:
It seems we misunderstood each other, I talked about DWARF_INFO_GET_MEMBER_OFFSET:
case DWARF_INFO_GET_MEMBER_OFFSET:
if ((!name) || strcmp(name, dwarf_info.member_name))
continue;
/*
* Get the member offset.
*/
if (dwarf_tag(die) == DW_TAG_union_type)
offset = 0;
else if (!get_data_member_location(walker, &offset))
continue;
dwarf_info.member_offset = offset;
return TRUE;
And about your code:
> case DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION:
> if (!get_die_type(walker, &die_type))
> continue;
> if (dwarf_tag(&die_type) != DW_TAG_union_type)
> continue;
>
> /*
> * At this point it is clear that this is a union.
> * Though unions have no offset elements (the offset
> * is always 0. So get_data_member_location would fail.
> */
> dwarf_info.member_offset = 0;
> return TRUE;
It's wrong that unions have no offset elements.
Correctly, members of union have no offset elements.
So, I'll fix it similarly to DWARF_INFO_GET_MEMBER_OFFSET:
case DWARF_INFO_GET_MEMBER_OFFSET_1ST_UNION:
if (!get_die_type(walker, &die_type))
continue;
if (dwarf_tag(&die_type) != DW_TAG_union_type)
continue;
/*
* Get the member offset.
*/
if (dwarf_tag(die) == DW_TAG_union_type)
offset = 0;
else if (!get_data_member_location(walker, &offset))
continue;
dwarf_info.member_offset = offset;
return TRUE;
Thanks
Atsushi Kumagai
> >
> >
> > Thanks
> > Atsushi Kumagai
> >
> >>> + offset = 0;
> >>> + else if (!get_data_member_location(walker, &offset))
> >>> continue;
> >>> dwarf_info.member_offset = offset;
> >>> return TRUE;
> >>>
> >>>
> >>> Unless you have better way to fix this issue, I'll merge your patch into
> >>> the next version with the change above.
> >>>
> >>> By the way, this fix enable us also to get the offset of page._mapcount and
> >>> page.private, it's very helpful for the new method of free page filtering.
> >>>
> >>> http://lists.infradead.org/pipermail/kexec/2012-June/006441.html
> >>>
> >>>
> >>> Thanks
> >>> Atsushi Kumagai
