gold/README

   1 gold is an ELF linker.  It is intended to have complete support for
   2 ELF and to run as fast as possible on modern systems.  For normal use
   3 it is a drop-in replacement for the older GNU linker.
   4
   5 gold is part of the GNU binutils.  See ../binutils/README for more
   6 general notes, including where to send bug reports.
   7
   8 gold was originally developed at Google, and was contributed to the
   9 Free Software Foundation in March 2008.  At Google it was designed by
  10 Ian Lance Taylor, with major contributions by Cary Coutant, Craig
  11 Silverstein, and Andrew Chatham.
  12
  13 The existing GNU linker manual is intended to be accurate
  14 documentation for features which gold supports.  gold supports most of
  15 the features of the GNU linker for ELF targets.  Notable
  16 omissions--features of the GNU linker not currently supported in
  17 gold--are:
  18   * MEMORY regions in linker scripts
  19   * MRI compatible linker scripts
  20   * linker map files (-M, -Map)
  21   * cross-reference reports (--cref)
  22   * linker garbage collection (--gc-sections)
  23   * position independent executables (-pie)
  24   * various other minor options
  25
  26
  27 Notes on the code
  28 =================
  29
  30 These are some notes which may be helpful to people working on the
  31 source code of gold itself.
  32
  33 gold is written in C++.  It is a GNU program, and therefore follows
  34 the GNU formatting standards as modified for C++.  Source documents in
  35 order of decreasing precedence:
  36     http://www.gnu.org/prep/standards/
  37     http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/C++STYLE
  38     http://www.zembu.com/eng/procs/c++style.html
  39
  40 The linker is intended to have complete support for cross-compilation,
  41 while still supporting the normal case of native linking as fast as
  42 possible.  In order to do this, many classes are actually templates
  43 whose parameter is the ELF file class (e.g., 32 bits or 64 bits).  The
  44 C++ code is the same, but we don't pay the execution time cost of
  45 always using 64-bit integers if the target is 32 bits.  Many of these
  46 class templates also have an endianness parameter: true for
  47 big-endian, false for little-endian.
  48
  49 The linker is multi-threaded.  The Task class represents a single unit
  50 of work.  Task objects are stored on a single Workqueue object.  Tasks
  51 communicate via Task_token objects.  Task_token objects are only
  52 manipulated while holding the master Workqueue lock.  Relatively few
  53 mutexes are used.