os_defines.h

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// Specific definitions for GNU/Linux  -*- C++ -*-
 
// Copyright (C) 2000-2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.
 
/** @file bits/os_defines.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{iosfwd}
 */
 
#ifndef _GLIBCXX_OS_DEFINES
#define _GLIBCXX_OS_DEFINES 1
 
// System-specific #define, typedefs, corrections, etc, go here.  This
// file will come before all others.
 
// This keeps isanum, et al from being propagated as macros.
#define __NO_CTYPE 1
 
#include <features.h>
 
// Provide a declaration for the possibly deprecated gets function, as
// glibc 2.15 and later does not declare gets for ISO C11 when
// __GNU_SOURCE is defined.
#if __GLIBC_PREREQ(2,15) && defined(_GNU_SOURCE)
# undef _GLIBCXX_HAVE_GETS
#endif
 
// Glibc 2.23 removed the obsolete isinf and isnan declarations. Check the
// version dynamically in case it has changed since libstdc++ was configured.
#define _GLIBCXX_NO_OBSOLETE_ISINF_ISNAN_DYNAMIC __GLIBC_PREREQ(2,23)
 
#if __GLIBC_PREREQ(2, 27)
// Since glibc 2.27 pthread_self() is usable without linking to libpthread.
# define _GLIBCXX_NATIVE_THREAD_ID pthread_self()
#else
// Before then it was in libc.so.6 but not libc.a, and always returns 0,
// which breaks the invariant this_thread::get_id() != thread::id{}.
// So only use it if we know the libpthread version is available.
// Otherwise use (__gthread_t)1 as the ID of the main (and only) thread.
# define _GLIBCXX_NATIVE_THREAD_ID \
  (__gthread_active_p() ? __gthread_self() : (__gthread_t)1)
#endif
 
#endif