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Re: [patch 2/7] [gold] Modify dwarf reader to get size and endianness from the object instead of from the parameters.


On Thu, Oct 18, 2012 at 11:35 AM, Ian Lance Taylor <iant@google.com> wrote:
> On Thu, Oct 18, 2012 at 11:16 AM, Cary Coutant <ccoutant@google.com> wrote:
>> This patch modifies the dwarf reader to get size and endianness from
>> the Relobj object instead of from the global parameters (which requires
>> an initialized target).
>>
>> gold/
>>         * dwarf_reader.cc (make_elf_reloc_mapper): Check size and endianness
>>         from object, not parameters.
>>         (Dwarf_info_reader::parse): Likewise.
>>         * object.h (Relobj::elfsize, Relobj::is_big_endian): New methods.
>>         (Relobj::do_elfsize, Relobj::do_is_big_endian): New methods.
>>         (Sized_relobj::do_elfsize, Sized_relobj::do_is_big_endian): New
>>         methods.
>
> I don't quite understand how this works.  You're changing
> make_elf_reloc_mapper to take a Relobj.  But it is called from
> Dwarf_info_reader::do_parse passing this->object_, and
> Dwarf_info_reader::object_ is an Object, not a relobj.  It's clearly
> important that Dwarf_info_reader continue to work for Dynobj as well
> as Relobj.  That's not a major issue as a Dynobj presumably doesn't
> need a reloc mapper.  But it seems that something is missing somewhere
> here.

Dwarf_info_reader::object_ is a Relobj*, not an Object*. It doesn't
currently support Dynobj objects, but you make a good point that it
ought to. I can rework that in a future patch.

Sized_dwarf_line_info, on the other hand, does support Dynobj objects,
and takes an Object*, but when it creates a reloc mapper, it creates a
new Sized_elf_reloc_mapper, which still takes an Object*. I've only
changed make_elf_reloc_mapper, which now needs to call
Relobj::elf_size() and Relobj::is_big_endian(), but then passes the
Relobj* as an Object* when creating the actual reloc mapper.

I could get around this (and probably will have to in order to support
Dwarf_info_reader for Dynobj objects) by promoting elf_size() and
is_big_endian() to the Object class.

OK with you to defer that for a follow-up patch?

-cary


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