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1 .. Copyright (C) 2015-2016 Free Software Foundation, Inc.
2 Originally contributed by David Malcolm <dmalcolm@redhat.com>
3
4 This is free software: you can redistribute it and/or modify it
5 under the terms of the GNU General Public License as published by
6 the Free Software Foundation, either version 3 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful, but
10 WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see
16 <http://www.gnu.org/licenses/>.
17
18 .. default-domain:: c
19
20 ABI and API compatibility
21 =========================
22
23 The libgccjit developers strive for ABI and API backward-compatibility:
24 programs built against libgccjit.so stand a good chance of running
25 without recompilation against newer versions of libgccjit.so, and
26 ought to recompile without modification against newer versions of
27 libgccjit.h.
28
29 .. note:: The libgccjit++.h C++ API is more experimental, and less
30 locked-down at this time.
31
32 API compatibility is achieved by extending the API rather than changing
33 it. For ABI compatiblity, we avoid bumping the SONAME, and instead use
34 symbol versioning to tag each symbol, so that a binary linked against
35 libgccjit.so is tagged according to the symbols that it uses.
36
37 For example, :func:`gcc_jit_context_add_command_line_option` was added in
38 ``LIBGCCJIT_ABI_1``. If a client program uses it, this can be detected
39 from metadata by using ``objdump``:
40
41 .. code-block:: bash
42
43 $ objdump -p testsuite/jit/test-extra-options.c.exe | tail -n 8
44
45 Version References:
46 required from libgccjit.so.0:
47 0x00824161 0x00 04 LIBGCCJIT_ABI_1
48 0x00824160 0x00 03 LIBGCCJIT_ABI_0
49 required from libc.so.6:
50
51 You can see the symbol tags provided by libgccjit.so using ``objdump``:
52
53 .. code-block:: bash
54
55 $ objdump -p libgccjit.so | less
56 [...snip...]
57 Version definitions:
58 1 0x01 0x0ff81f20 libgccjit.so.0
59 2 0x00 0x00824160 LIBGCCJIT_ABI_0
60 3 0x00 0x00824161 LIBGCCJIT_ABI_1
61 LIBGCCJIT_ABI_0
62 [...snip...]
63
64 ABI symbol tags
65 ***************
66
67 The initial release of libgccjit (in gcc 5.1) did not use symbol versioning.
68
69 Newer releases use the following tags.
70
71 .. _LIBGCCJIT_ABI_0:
72
73 ``LIBGCCJIT_ABI_0``
74 -------------------
75
76 All entrypoints in the initial release of libgccjit are tagged with
77 ``LIBGCCJIT_ABI_0``, to signify the transition to symbol versioning.
78
79 Binaries built against older copies of ``libgccjit.so`` should
80 continue to work, with this being handled transparently by the linker
81 (see `this post
82 <https://gcc.gnu.org/ml/gcc-patches/2015-06/msg02126.html>`_)
83
84 .. _LIBGCCJIT_ABI_1:
85
86 ``LIBGCCJIT_ABI_1``
87 -------------------
88 ``LIBGCCJIT_ABI_1`` covers the addition of
89 :func:`gcc_jit_context_add_command_line_option`
90
91 .. _LIBGCCJIT_ABI_2:
92
93 ``LIBGCCJIT_ABI_2``
94 -------------------
95 ``LIBGCCJIT_ABI_2`` covers the addition of
96 :func:`gcc_jit_context_set_bool_allow_unreachable_blocks`
97
98 .. _LIBGCCJIT_ABI_3:
99
100 ``LIBGCCJIT_ABI_3``
101 -------------------
102 ``LIBGCCJIT_ABI_3`` covers the addition of switch statements via API
103 entrypoints:
104
105 * :func:`gcc_jit_block_end_with_switch`
106
107 * :func:`gcc_jit_case_as_object`
108
109 * :func:`gcc_jit_context_new_case`
110
111 .. _LIBGCCJIT_ABI_4:
112
113 ``LIBGCCJIT_ABI_4``
114 -------------------
115 ``LIBGCCJIT_ABI_4`` covers the addition of timers via API
116 entrypoints:
117
118 * :func:`gcc_jit_context_get_timer`
119
120 * :func:`gcc_jit_context_set_timer`
121
122 * :func:`gcc_jit_timer_new`
123
124 * :func:`gcc_jit_timer_release`
125
126 * :func:`gcc_jit_timer_push`
127
128 * :func:`gcc_jit_timer_pop`
129
130 * :func:`gcc_jit_timer_print`
131
132 .. _LIBGCCJIT_ABI_5:
133
134 ``LIBGCCJIT_ABI_5``
135 -------------------
136 ``LIBGCCJIT_ABI_5`` covers the addition of
137 :func:`gcc_jit_context_set_bool_use_external_driver`