[gold patch] Incremental 16/18: COMDAT groups

[Cary Coutant]

>>       * incremental-dump.cc (dump_incremental_inputs): Print COMDAT groups.
>>       * incremental.cc (Incremental_inputs::report_input_section): Fix
>>       comment, indentation.
>>       (Incremental_inputs::report_comdat_group): New function.
>>       (Output_section_incremental_inputs::set_final_data_size): Adjust size
>>       of data for incremental input file entry.
>>       (Output_section_incremental_inputs::write_info_blocks): Write COMDAT
>>       group count, COMDAT group signatures.
>>       (Sized_incr_relobj::do_layout): Record kept COMDAT group info from
>>       an unchanged input file.
>>       * incremental.h (Incremental_object_entry::Incremental_object_entry):
>>       Initialize new data member.
>>       (Incremental_object_entry::add_comdat_group): New function.
>>       (Incremental_object_entry::get_comdat_group_count): New function.
>>       (Incremental_object_entry::get_comdat_signature_key): New function.
>>       (Incremental_object_entry::groups_): New data member.
>>       (Incremental_inputs::report_comdat_group): New function.
>>       (Incremental_input_entry_reader::get_symbol_offset): Adjust size of
>>       data for incremental input file entry.
>>       (Incremental_input_entry_reader::get_comdat_group_count): New function.
>>       (Incremental_input_entry_reader::get_input_section): Adjust size of
>>       data for incremental input file entry.
>>       (Incremental_input_entry_reader::get_global_symbol_reader): Likewise.
>>       (Incremental_input_entry_reader::get_comdat_group_signature): New
>>       function.
>>       * object.cc (Sized_relobj::include_section_group): Report kept
>>       COMDAT groups for incremental links.
>
> This is OK.

Thanks, committed.

> At some point some of these 28's and other offsets ought to turn into
> named consts.  Or perhaps even go the elfcpp route.

Agreed. Those magic constants started out few and manageable, but
started spreading, and I should have done something about that. Sorry.

-cary