libelf/elf_version.c

   1 /* Coordinate ELF library and application versions.
   2    Copyright (C) 1998, 1999, 2000, 2002, 2015 Red Hat, Inc.
   3    This file is part of elfutils.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 1998.
   5
   6    This file is free software; you can redistribute it and/or modify
   7    it under the terms of either
   8
   9      * the GNU Lesser General Public License as published by the Free
  10        Software Foundation; either version 3 of the License, or (at
  11        your option) any later version
  12
  13    or
  14
  15      * the GNU General Public License as published by the Free
  16        Software Foundation; either version 2 of the License, or (at
  17        your option) any later version
  18
  19    or both in parallel, as here.
  20
  21    elfutils is distributed in the hope that it will be useful, but
  22    WITHOUT ANY WARRANTY; without even the implied warranty of
  23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  24    General Public License for more details.
  25
  26    You should have received copies of the GNU General Public License and
  27    the GNU Lesser General Public License along with this program.  If
  28    not, see <http://www.gnu.org/licenses/>.  */
  29
  30 #ifdef HAVE_CONFIG_H
  31 # include <config.h>
  32 #endif
  33
  34 #include <libelfP.h>
  35 #include <pthread.h>
  36
  37 /* Multiple threads may initialize __libelf_version.
  38    pthread_once() ensures that __libelf_version is initialized only once. */
  39 once_define(static, version_once);
  40
  41 /* Currently selected version.  Should be EV_CURRENT.
  42    Will be EV_NONE if elf_version () has not been called yet.  */
  43 unsigned int __libelf_version = EV_NONE;
  44
  45 static void initialize_version(void)
  46 {
  47   __libelf_version = EV_CURRENT;
  48 }
  49
  50 unsigned int
  51 elf_version (unsigned int version)
  52 {
  53   if (version == EV_NONE)
  54     return EV_CURRENT;
  55
  56   if (likely (version == EV_CURRENT))
  57     {
  58       /* Phew, we know this version.  */
  59
  60       /* Signal that the version is now initialized.  */
  61       once(version_once, initialize_version);
  62
  63       /* And return the last (or initial) version.  */
  64       return EV_CURRENT;
  65     }
  66
  67   /* We cannot handle this version.  */
  68   __libelf_seterrno (ELF_E_UNKNOWN_VERSION);
  69   return EV_NONE;
  70 }
  71 INTDEF(elf_version)