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bae7f79e | 1 | gold is an ELF linker. It is intended to have complete support for |
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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. | |
bae7f79e | 4 | |
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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 | |
874c5b28 | 20 | * cross-reference reports (--cref) |
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21 | * position independent executables (-pie) |
22 | * various other minor options | |
23 | ||
24 | ||
25 | Notes on the code | |
26 | ================= | |
27 | ||
28 | These are some notes which may be helpful to people working on the | |
29 | source code of gold itself. | |
30 | ||
31 | gold is written in C++. It is a GNU program, and therefore follows | |
32 | the GNU formatting standards as modified for C++. Source documents in | |
33 | order of decreasing precedence: | |
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34 | http://www.gnu.org/prep/standards/ |
35 | http://gcc.gnu.org/onlinedocs/libstdc++/17_intro/C++STYLE | |
36 | http://www.zembu.com/eng/procs/c++style.html | |
37 | ||
38 | The linker is intended to have complete support for cross-compilation, | |
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39 | while still supporting the normal case of native linking as fast as |
40 | possible. In order to do this, many classes are actually templates | |
41 | whose parameter is the ELF file class (e.g., 32 bits or 64 bits). The | |
42 | C++ code is the same, but we don't pay the execution time cost of | |
43 | always using 64-bit integers if the target is 32 bits. Many of these | |
44 | class templates also have an endianness parameter: true for | |
45 | big-endian, false for little-endian. | |
bae7f79e | 46 | |
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47 | The linker is multi-threaded. The Task class represents a single unit |
48 | of work. Task objects are stored on a single Workqueue object. Tasks | |
49 | communicate via Task_token objects. Task_token objects are only | |
50 | manipulated while holding the master Workqueue lock. Relatively few | |
51 | mutexes are used. | |
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52 | |
53 | ||
54 | Build requirements | |
55 | ================== | |
56 | ||
57 | The gold source code uses templates heavily. Building it requires a | |
58 | recent version of g++. g++ 4.0.3 is known to work. g++ 3.2 and g++ | |
59 | 3.4.3 are known to fail. | |
60 | ||
61 | The linker script parser uses features which are only in newer | |
62 | versions of bison. bison 2.3 is known to work. bison 1.26 is known | |
63 | to fail. If you are building gold from an official binutils release, | |
64 | the bison output should already be included. |