* arm.cc (Arm_input_section::Arm_input_section): For a
SHT_ARM_EXIDX section, always keeps the input sections.
(Arm_input_section::set_exidx_section_link): New method.
(Arm_exidx_input_section::Arm_exidx_input_section): Initialize
has_errors_ to false.
(Arm_exidx_input_section::has_errors,
Arm_exidx_input_section::set_has_errors): New methods.
(Arm_exidx_input_section::has_errors_): New data member.
(Arm_relobj::get_exidx_shndx_list): New method.
(Arm_output_section::append_text_sections_to_list): Do not skip
section without SHF_EXECINSTR.
(Arm_output_section::fix_exidx_coverage): Skip input sections with
errors.
(Arm_relobj::make_exidx_input_section): Add new parameter for text
section header. Make error messages more verbose. Check for
a non-executable section linked to an EXIDX section.
(Arm_relobj::do_read_symbols): Remove error checking, which has been
moved to Arm_relobj::make_exidx_input_section. Add an assertion to
check that there is no deferred EXIDX section if we exit early.
Instead of not making an EXIDX section in case of an error, make one
and set the has_errors flag of it.
(Target_arm::do_finalize_sections): Fix up links of EXIDX sections
in a relocatable link.
(Target_arm::do_relax): Look for the EXIDX output section instead of
assuming that it is called .ARM.exidx.
(Target_arm::fix_exidx_coverage): Add a new parameter for input
section list. Do not check for SHF_EXECINSTR section flags but
skip any input section with errors.
* output.cc (Output_section::Output_section): Initialize
always_keeps_input_sections_ to false.
(Output_section::add_input_section): Check for
always_keeps_input_sections_.
* output.h (Output_section::always_keeps_input_sections,
Output_section::set_always_keeps_input_sections): New methods.
(Output_section::always_keeps_input_sections): New data member.
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
* cross-reference reports (--cref)
* 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.
Build requirements
==================
The gold source code uses templates heavily. Building it requires a
recent version of g++. g++ 4.0.3 is known to work. g++ 3.2 and g++
3.4.3 are known to fail.
The linker script parser uses features which are only in newer
versions of bison. bison 2.3 is known to work. bison 1.26 is known
to fail. If you are building gold from an official binutils release,
the bison output should already be included.
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