1/* Macros for managing ABI-compatibility definitions using ELF symbol versions.
2 Copyright (C) 2000-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#ifndef _SHLIB_COMPAT_H
20#define _SHLIB_COMPAT_H 1
21
22# include <abi-versions.h>
23
24#ifdef SHARED
25
26/* The file abi-versions.h (generated by scripts/abi-versions.awk) defines
27 symbols like `ABI_libm_GLIBC_2_0' for each version set in the source
28 code for each library. For a version set that is subsumed by a later
29 version set, the definition gives the subsuming set, i.e. if GLIBC_2_0
30 is subsumed by GLIBC_2_1, then ABI_libm_GLIBC_2_0 == ABI_libm_GLIBC_2_1.
31 Each version set that is to be distinctly defined in the output has an
32 unique positive integer value, increasing with newer versions. Thus,
33 evaluating two ABI_* symbols reduces to integer values that differ only
34 when the two version sets named are in fact two different ABIs we are
35 supporting. If these do not differ, then there is no need to compile in
36 extra code to support this version set where it has been superseded by a
37 newer version. The compatibility code should be conditionalized with
38 e.g. `#if SHLIB_COMPAT (libm, GLIBC_2_0, GLIBC_2_2)' for code introduced
39 in the GLIBC_2.0 version and obsoleted in the GLIBC_2.2 version. */
40
41# define SHLIB_COMPAT(lib, introduced, obsoleted) \
42 _SHLIB_COMPAT (lib, introduced, obsoleted)
43# define _SHLIB_COMPAT(lib, introduced, obsoleted) \
44 (IS_IN (lib) \
45 && (!(ABI_##lib##_##obsoleted - 0) \
46 || ((ABI_##lib##_##introduced - 0) < (ABI_##lib##_##obsoleted - 0))))
47
48/* That header also defines symbols like `VERSION_libm_GLIBC_2_1' to
49 the version set name to use for e.g. symbols first introduced into
50 libm in the GLIBC_2.1 version. Definitions of symbols with explicit
51 versions should look like:
52 versioned_symbol (libm, new_foo, foo, GLIBC_2_1);
53 This will define the symbol `foo' with the appropriate default version,
54 i.e. either GLIBC_2.1 or the "earliest version" specified in
55 shlib-versions if that is newer. */
56
57# define versioned_symbol(lib, local, symbol, version) \
58 versioned_symbol_1 (lib, local, symbol, version)
59# define versioned_symbol_1(lib, local, symbol, version) \
60 versioned_symbol_2 (local, symbol, VERSION_##lib##_##version)
61# define versioned_symbol_2(local, symbol, name) \
62 default_symbol_version (local, symbol, name)
63
64# define compat_symbol(lib, local, symbol, version) \
65 compat_symbol_reference (lib, local, symbol, version)
66
67/* This is similar to compat_symbol, but allows versioning the same symbol
68 to multiple version without having multiple symbol definitions. For
69 instance:
70
71 #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
72 compat_symbol_unique (libc, old_foo, GLIBC_2_1_2)
73 #endif
74
75 #if (SHLIB_COMPAT (libpthread, GLIBC_2_2_6, GLIBC_2_3))
76 compat_symbol_unique (libc, old_foo, GLIBC_2_2_6)
77 #endif
78
79 Internally it creates a unique strong alias to the input symbol and
80 creates one compat_symbol on the alias. Using the above example,
81 it is similar to:
82
83 #if (SHLIB_COMPAT (libpthread, GLIBC_2_1_2, GLIBC_2_2))
84 strong_alias (old_foo, old_foo__COUNTER__)
85 compat_symbol (libc, old_foo__COUNTER__, foo, GLIBC_2_2)
86 #endif.
87
88 With __COUNTER__ being a monotonic number generated by the compiler. */
89
90# define __compat_symbol_unique_concat(x, y) x ## y
91# define _compat_symbol_unique_concat(x, y) \
92 __compat_symbol_unique_concat (x, y)
93# define _compat_symbol_unique_alias(name) \
94 _compat_symbol_unique_concat (name, __COUNTER__)
95# define _compat_symbol_unique(lib, orig_name, name, version) \
96 strong_alias (orig_name, name) \
97 compat_symbol (lib, name, orig_name, version)
98# define compat_symbol_unique(lib, name, version) \
99 _compat_symbol_unique (lib, name, _compat_symbol_unique_alias (name), \
100 version)
101
102#else
103
104/* Not compiling ELF shared libraries at all, so never any old versions. */
105# define SHLIB_COMPAT(lib, introduced, obsoleted) 0
106
107/* No versions to worry about, just make this the global definition. */
108# define versioned_symbol(lib, local, symbol, version) \
109 weak_alias (local, symbol)
110
111/* This should not appear outside `#if SHLIB_COMPAT (...)'. */
112# define compat_symbol(lib, local, symbol, version) ...
113# define compat_symbol_unique(lib, name, version) ...
114
115#endif
116
117/* Use compat_symbol_reference for a reference *or* definition of a
118 specific version of a symbol. Definitions are primarily used to
119 ensure tests reference the exact compat symbol required, or define an
120 interposing symbol of the right version e.g. __malloc_initialize_hook
121 in mcheck-init.c. Use compat_symbol to define such a symbol within
122 the shared libraries that are built for users. */
123#define compat_symbol_reference(lib, local, symbol, version) \
124 compat_symbol_reference_1 (lib, local, symbol, version)
125#define compat_symbol_reference_1(lib, local, symbol, version) \
126 compat_symbol_reference_2 (local, symbol, VERSION_##lib##_##version)
127#define compat_symbol_reference_2(local, symbol, name) \
128 symbol_version_reference (local, symbol, name)
129
130/* Export the symbol only for shared-library compatibility. */
131#define libc_sunrpc_symbol(name, aliasname, version) \
132 compat_symbol (libc, name, aliasname, version);
133
134/* The TEST_COMPAT macro acts just like the SHLIB_COMPAT macro except
135 that it does not check IS_IN. It is used by tests that are testing
136 functionality that is only available in specific GLIBC versions. */
137
138# define TEST_COMPAT(lib, introduced, obsoleted) \
139 _TEST_COMPAT (lib, introduced, obsoleted)
140# define _TEST_COMPAT(lib, introduced, obsoleted) \
141 (!(ABI_##lib##_##obsoleted - 0) \
142 || ((ABI_##lib##_##introduced - 0) < (ABI_##lib##_##obsoleted - 0)))
143
144#endif /* shlib-compat.h */
145