include/shlib-compat.h

   1 /* Macros for managing ABI-compatibility definitions using ELF symbol versions.
   2    Copyright (C) 2000, 2002 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #ifndef _SHLIB_COMPAT_H
  21 #define _SHLIB_COMPAT_H 1
  22
  23 #if defined HAVE_ELF && defined DO_VERSIONING
  24 /* Since there is just one set of .d files generated, we need to
  25    include this unconditionally to have the dependency noticed properly.  */
  26 #include <abi-versions.h>       /* header generated by abi-versions.awk */
  27 #endif
  28
  29 #if defined HAVE_ELF && defined SHARED && defined DO_VERSIONING
  30
  31 /* The file abi-versions.h (generated by scripts/abi-versions.awk) defines
  32    symbols like `ABI_libm_GLIBC_2_0' for each version set in the source
  33    code for each library.  For a version set that is subsumed by a later
  34    version set, the definition gives the subsuming set, i.e. if GLIBC_2_0
  35    is subsumed by GLIBC_2_1, then ABI_libm_GLIBC_2_0 == ABI_libm_GLIBC_2_1.
  36    Each version set that is to be distinctly defined in the output has an
  37    unique positive integer value, increasing with newer versions.  Thus,
  38    evaluating two ABI_* symbols reduces to integer values that differ only
  39    when the two version sets named are in fact two different ABIs we are
  40    supporting.  If these do not differ, then there is no need to compile in
  41    extra code to support this version set where it has been superseded by a
  42    newer version.  The compatibility code should be conditionalized with
  43    e.g. `#if SHLIB_COMPAT (libm, GLIBC_2_0, GLIBC_2_2)' for code introduced
  44    in the GLIBC_2.0 version and obsoleted in the GLIBC_2.2 version.  */
  45
  46 # define SHLIB_COMPAT(lib, introduced, obsoleted)                             \
  47   ((IS_IN_##lib - 0)                                                          \
  48    && (!(ABI_##lib##_##obsoleted - 0)                                         \
  49        || ((ABI_##lib##_##introduced - 0) < (ABI_##lib##_##obsoleted - 0))))
  50
  51 # ifndef NOT_IN_libc
  52 #  define IS_IN_libc 1
  53 # endif
  54
  55 /* That header also defines symbols like `VERSION_libm_GLIBC_2_1' to
  56    the version set name to use for e.g. symbols first introduced into
  57    libm in the GLIBC_2.1 version.  Definitions of symbols with explicit
  58    versions should look like:
  59         versioned_symbol (libm, new_foo, foo, GLIBC_2_1);
  60    This will define the symbol `foo' with the appropriate default version,
  61    i.e. either GLIBC_2.1 or the "earliest version" specified in
  62    shlib-versions if that is newer.  */
  63
  64 # define versioned_symbol(lib, local, symbol, version) \
  65   versioned_symbol_1 (local, symbol, VERSION_##lib##_##version)
  66 # define versioned_symbol_1(local, symbol, name) \
  67   default_symbol_version (local, symbol, name)
  68
  69 # define compat_symbol(lib, local, symbol, version) \
  70   compat_symbol_1 (local, symbol, VERSION_##lib##_##version)
  71 # define compat_symbol_1(local, symbol, name) \
  72   symbol_version (local, symbol, name)
  73
  74 #else
  75
  76 /* Not compiling ELF shared libraries at all, so never any old versions.  */
  77 # define SHLIB_COMPAT(lib, introduced, obsoleted)       0
  78
  79 /* No versions to worry about, just make this the global definition.  */
  80 # define versioned_symbol(lib, local, symbol, version) \
  81   weak_alias (local, symbol)
  82
  83 /* This should not appear outside `#if SHLIB_COMPAT (...)'.  */
  84 # define compat_symbol(lib, local, symbol, version) ...
  85
  86 #endif
  87
  88
  89 #endif  /* shlib-compat.h */