On 06.08.2012 07:54, Atsushi Kumagai wrote: > Hello Stefan, > > On Thu, 02 Aug 2012 10:23:13 +0200 > Stefan Bader <[email protected]> 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:
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;
>
>
> 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
>>>
>>
>>
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