info section.
(Layout::add_comdat): Add new parameters. Change type
of signature parameter. Add object and shndx to signatures table.
(Layout::find_kept_object): New function.
* layout.h: Include <cstring>.
(Layout::is_debug_info_section): New function.
(Layout::add_comdat): Add new parameters.
(Layout::find_kept_object): New function.
(Layout::Kept_section): New struct.
(Layout::Signatures): Change type of map range.
* object.cc (Relobj::output_section_address): New function.
(Sized_relobj::include_section_group): Add new parameters. Change
calls to Layout::add_comdat. Change to build table of kept comdat
groups and table mapping discarded sections to kept sections.
(Sized_relobj::include_linkonce_section): Likewise. Add new parameter.
(Sized_relobj::do_layout): Change calls to include_section_group and
include_linkonce_section.
(Sized_relobj::do_finalize_local_symbols): Do not set local symbol
value to zero when section is discarded.
(Sized_relobj::map_to_kept_section): New function.
* object.h (Relobj::output_section_address): New function.
(Relobj::Comdat_group): New type.
(Relobj::find_comdat_group): New function.
(Relobj::Comdat_group_table): New type.
(Relobj::Kept_comdat_section): New type.
(Relobj::Kept_comdat_section_table): New type.
(Relobj::add_comdat_group): New function.
(Relobj::set_kept_comdat_section): New function.
(Relobj::get_kept_comdat_section): New function.
(Relobj::comdat_groups_): New field.
(Relobj::kept_comdat_sections_): New field.
(Symbol_value::input_value): Update comment.
(Sized_relobj::map_to_kept_section) New function.
(Sized_relobj::include_linkonce_section): Add new parameter.
* target-reloc.h (Comdat_behavior): New type.
(get_comdat_behavior): New function.
(relocate_section): Add code to map a discarded section to the
corresponding kept section when applying a relocation.
gold is an ELF linker. It is intended to have complete support for
ELF and to run as fast as possible on modern systems. For normal use
it is a drop-in replacement for the older GNU linker.
gold is part of the GNU binutils. See ../binutils/README for more
general notes, including where to send bug reports.
gold was originally developed at Google, and was contributed to the
Free Software Foundation in March 2008. At Google it was designed by
Ian Lance Taylor, with major contributions by Cary Coutant, Craig
Silverstein, and Andrew Chatham.
The existing GNU linker manual is intended to be accurate
documentation for features which gold supports. gold supports most of
the features of the GNU linker for ELF targets. Notable
omissions--features of the GNU linker not currently supported in
gold--are:
* MEMORY regions in linker scripts
* MRI compatible linker scripts
* linker map files (-M, -Map)
* cross-reference reports (--cref)
* linker garbage collection (--gc-sections)
* position independent executables (-pie)
* various other minor options
Notes on the code
=================
These are some notes which may be helpful to people working on the
source code of gold itself.
gold is written in C++. It is a GNU program, and therefore follows
the GNU formatting standards as modified for C++. Source documents in
order of decreasing precedence:
http://www.gnu.org/prep/standards/
http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/C++STYLE
http://www.zembu.com/eng/procs/c++style.html
The linker is intended to have complete support for cross-compilation,
while still supporting the normal case of native linking as fast as
possible. In order to do this, many classes are actually templates
whose parameter is the ELF file class (e.g., 32 bits or 64 bits). The
C++ code is the same, but we don't pay the execution time cost of
always using 64-bit integers if the target is 32 bits. Many of these
class templates also have an endianness parameter: true for
big-endian, false for little-endian.
The linker is multi-threaded. The Task class represents a single unit
of work. Task objects are stored on a single Workqueue object. Tasks
communicate via Task_token objects. Task_token objects are only
manipulated while holding the master Workqueue lock. Relatively few
mutexes are used.
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