1.. Copyright (C) 2015-2020 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
20ABI and API compatibility
21=========================
22
23The libgccjit developers strive for ABI and API backward-compatibility:
24programs built against libgccjit.so stand a good chance of running
25without recompilation against newer versions of libgccjit.so, and
26ought to recompile without modification against newer versions of
27libgccjit.h.
28
29.. note:: The libgccjit++.h C++ API is more experimental, and less
30          locked-down at this time.
31
32API compatibility is achieved by extending the API rather than changing
33it.  For ABI compatiblity, we avoid bumping the SONAME, and instead use
34symbol versioning to tag each symbol, so that a binary linked against
35libgccjit.so is tagged according to the symbols that it uses.
36
37For 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
39from 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
51You 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
64Programmatically checking version
65***************
66
67Client code can programmatically check libgccjit version using:
68
69.. function::  int gcc_jit_version_major (void)
70
71   Return libgccjit major version.  This is analogous to __GNUC__ in C code.
72
73.. function::  int gcc_jit_version_minor (void)
74
75   Return libgccjit minor version.  This is analogous to
76   __GNUC_MINOR__ in C code.
77
78.. function::  int gcc_jit_version_patchlevel (void)
79
80   Return libgccjit patchlevel version.  This is analogous to
81   __GNUC_PATCHLEVEL__ in C code.
82
83.. note:: These entry points has been added with ``LIBGCCJIT_ABI_13``
84          (see below).
85
86ABI symbol tags
87***************
88
89The initial release of libgccjit (in gcc 5.1) did not use symbol versioning.
90
91Newer releases use the following tags.
92
93.. _LIBGCCJIT_ABI_0:
94
95``LIBGCCJIT_ABI_0``
96-------------------
97
98All entrypoints in the initial release of libgccjit are tagged with
99``LIBGCCJIT_ABI_0``, to signify the transition to symbol versioning.
100
101Binaries built against older copies of ``libgccjit.so`` should
102continue to work, with this being handled transparently by the linker
103(see `this post
104<https://gcc.gnu.org/ml/gcc-patches/2015-06/msg02126.html>`_)
105
106.. _LIBGCCJIT_ABI_1:
107
108``LIBGCCJIT_ABI_1``
109-------------------
110``LIBGCCJIT_ABI_1`` covers the addition of
111:func:`gcc_jit_context_add_command_line_option`
112
113.. _LIBGCCJIT_ABI_2:
114
115``LIBGCCJIT_ABI_2``
116-------------------
117``LIBGCCJIT_ABI_2`` covers the addition of
118:func:`gcc_jit_context_set_bool_allow_unreachable_blocks`
119
120.. _LIBGCCJIT_ABI_3:
121
122``LIBGCCJIT_ABI_3``
123-------------------
124``LIBGCCJIT_ABI_3`` covers the addition of switch statements via API
125entrypoints:
126
127  * :func:`gcc_jit_block_end_with_switch`
128
129  * :func:`gcc_jit_case_as_object`
130
131  * :func:`gcc_jit_context_new_case`
132
133.. _LIBGCCJIT_ABI_4:
134
135``LIBGCCJIT_ABI_4``
136-------------------
137``LIBGCCJIT_ABI_4`` covers the addition of timers via API
138entrypoints:
139
140  * :func:`gcc_jit_context_get_timer`
141
142  * :func:`gcc_jit_context_set_timer`
143
144  * :func:`gcc_jit_timer_new`
145
146  * :func:`gcc_jit_timer_release`
147
148  * :func:`gcc_jit_timer_push`
149
150  * :func:`gcc_jit_timer_pop`
151
152  * :func:`gcc_jit_timer_print`
153
154.. _LIBGCCJIT_ABI_5:
155
156``LIBGCCJIT_ABI_5``
157-------------------
158``LIBGCCJIT_ABI_5`` covers the addition of
159:func:`gcc_jit_context_set_bool_use_external_driver`
160
161.. _LIBGCCJIT_ABI_6:
162
163``LIBGCCJIT_ABI_6``
164-------------------
165``LIBGCCJIT_ABI_6`` covers the addition of
166:func:`gcc_jit_rvalue_set_bool_require_tail_call`
167
168.. _LIBGCCJIT_ABI_7:
169
170``LIBGCCJIT_ABI_7``
171-------------------
172``LIBGCCJIT_ABI_7`` covers the addition of
173:func:`gcc_jit_type_get_aligned`
174
175.. _LIBGCCJIT_ABI_8:
176
177``LIBGCCJIT_ABI_8``
178-------------------
179``LIBGCCJIT_ABI_8`` covers the addition of
180:func:`gcc_jit_type_get_vector`
181
182.. _LIBGCCJIT_ABI_9:
183
184``LIBGCCJIT_ABI_9``
185-------------------
186``LIBGCCJIT_ABI_9`` covers the addition of
187:func:`gcc_jit_function_get_address`
188
189.. _LIBGCCJIT_ABI_10:
190
191``LIBGCCJIT_ABI_10``
192--------------------
193``LIBGCCJIT_ABI_10`` covers the addition of
194:func:`gcc_jit_context_new_rvalue_from_vector`
195
196.. _LIBGCCJIT_ABI_11:
197
198``LIBGCCJIT_ABI_11``
199--------------------
200``LIBGCCJIT_ABI_11`` covers the addition of
201:func:`gcc_jit_context_add_driver_option`
202
203``LIBGCCJIT_ABI_12``
204--------------------
205``LIBGCCJIT_ABI_12`` covers the addition of
206:func:`gcc_jit_context_new_bitfield`
207
208``LIBGCCJIT_ABI_13``
209--------------------
210``LIBGCCJIT_ABI_13`` covers the addition of version functions via API
211entrypoints:
212
213  * :func:`gcc_jit_version_major`
214
215  * :func:`gcc_jit_version_minor`
216
217  * :func:`gcc_jit_version_patchlevel`
218