libstdc++: os_defines.h Source File

libstdc++

os_defines.h
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1// Specific definitions for GNU/Linux -*- C++ -*-
2
3// Copyright (C) 2000-2026 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/os_defines.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{iosfwd}
28 */
29
30#ifndef _GLIBCXX_OS_DEFINES
31#define _GLIBCXX_OS_DEFINES 1
32
33// System-specific #define, typedefs, corrections, etc, go here. This
34// file will come before all others.
35
36// This keeps isalnum, et al from being propagated as macros.
37#define __NO_CTYPE 1
38
39#include <features.h>
40
41// Provide a declaration for the possibly deprecated gets function, as
42// glibc 2.15 and later does not declare gets for ISO C11 when
43// __GNU_SOURCE is defined.
44#if __GLIBC_PREREQ(2,15) && defined(_GNU_SOURCE)
45# undef _GLIBCXX_HAVE_GETS
46#endif
47
48// Glibc 2.23 removed the obsolete isinf and isnan declarations. Check the
49// version dynamically in case it has changed since libstdc++ was configured.
50#define _GLIBCXX_NO_OBSOLETE_ISINF_ISNAN_DYNAMIC __GLIBC_PREREQ(2,23)
51
52// Glibc 2.26 on i?86/x86-64/ia64/ppc64le added *f128 support.
53// Glibc 2.27 added it also on many other arches but those have IEEE quad
54// long double.
55#if __GLIBC_PREREQ(2, 26) \
56 && (defined(__i386__) || defined(__x86_64__) || defined (__ia64__) \
57 || (defined(__powerpc__) && defined(_ARCH_PWR8) \
58 && defined(__LITTLE_ENDIAN__) && (_CALL_ELF == 2) \
59 && defined(__FLOAT128__)))
60# define _GLIBCXX_HAVE_FLOAT128_MATH 1
61#endif
62
63// Enable __cxa_thread_atexit to rely on a (presumably libc-provided)
64// __cxa_thread_atexit_impl, if it happens to be defined, even if
65// configure couldn't find it during the build.
66#define _GLIBCXX_MAY_HAVE___CXA_THREAD_ATEXIT_IMPL 1
67
68#ifdef __linux__
69// The following libpthread properties only apply to Linux, not GNU/Hurd.
70
71# if __GLIBC_PREREQ(2, 27)
72// Since glibc 2.27 pthread_self() is usable without linking to libpthread.
73# define _GLIBCXX_NATIVE_THREAD_ID pthread_self()
74# else
75// Before then it was in libc.so.6 but not libc.a, and always returns 0,
76// which breaks the invariant this_thread::get_id() != thread::id{}.
77// So only use it if we know the libpthread version is available.
78// Otherwise use (__gthread_t)1 as the ID of the main (and only) thread.
79# define _GLIBCXX_NATIVE_THREAD_ID \
80 (__gthread_active_p() ? __gthread_self() : (__gthread_t)1)
81# endif
82
83# if __GLIBC_PREREQ(2, 34)
84// Since glibc 2.34 all pthreads functions are usable without linking to
85// libpthread.
86# define _GLIBCXX_GTHREAD_USE_WEAK 0
87# endif
88#endif // __linux__
89
90#endif
features.h
Defines on whether to include algorithm variants.