When --build-id=tree is selected, gold would schedule a set of
tasks to run to compute md5 hashes in parallel on chunks of the
file. The scheduling was done before the
Write_after_input_sections_task ran, so if we are compressing
debug sections, the output file will change size and be remapped
to a new address, sometimes causing the build id computation to
crash, but even when it doesn't crash, it wouldn't include the
debug information in the hash computation.
This patch delays the scheduling of the md5 tasks until after
Write_after_input_sections_task.
gold/
PR gold/17819
* gold.cc (queue_final_tasks): When --build-id=tree, queue a
separate task to schedule the build id computation.
* layout.cc (Hash_task::Hash_task): Remove build_id_blocker,
add Output_file and offset.
(Hash_task::run): Get and release the input views.
(Hash_task::is_runnable): Always return NULL (always runnable).
(Layout::queue_build_id_tasks): Remove.
(Layout::write_build_id): Add array_of_hashes and size_of_hashes
parameters; use them instead of class members.
(Build_id_task_runner::run): New function.
(Close_task_runner::run): Pass array_of_hashes and size_of_hashes
to write_build_id.
* layout.h (Layout::queue_build_id_tasks): Remove.
(Layout::write_build_id): Add array_of_hashes and size_of_hashes
parameters.
(Layout::array_of_hashes_): Remove.
(Layout::size_of_array_of_hashes_): Remove.
(Layout::input_view_): Remove.
(Build_id_task_runner): New class.
(Close_task_runner::Close_task_runner): Add array_of_hashes and
size_of_hashes parameters.
(Close_task_runner::array_of_hashes_): New data member.
(Close_task_runner::size_of_hashes_): New data member.
* testsuite/Makefile.am
(flagstest_compress_debug_sections_and_build_id_tree): New test.
* testsuite/Makefile.in: Regenerate.
This file contains invisible Unicode characters that are indistinguishable to humans but may be processed differently by a computer. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.
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:
* 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++/manual/source_code_style.html
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 and 4.1.3 are known to work. g++
3.2, 3.4.3, and 4.1.2 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.
Copyright (C) 2012-2015 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
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