// Predefined symbols and macros -*- C++ -*-

// Copyright (C) 1997-2020 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/c++config.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{version}
 */

#ifndef _GLIBCXX_CXX_CONFIG_H
#define _GLIBCXX_CXX_CONFIG_H 1

// The major release number for the GCC release the C++ library belongs to.
#define _GLIBCXX_RELEASE

// The datestamp of the C++ library in compressed ISO date format.
#define __GLIBCXX__

// Macros for various attributes.
//   _GLIBCXX_PURE
//   _GLIBCXX_CONST
//   _GLIBCXX_NORETURN
//   _GLIBCXX_NOTHROW
//   _GLIBCXX_VISIBILITY
#ifndef _GLIBCXX_PURE
# define _GLIBCXX_PURE __attribute__ ((__pure__))
#endif

#ifndef _GLIBCXX_CONST
# define _GLIBCXX_CONST __attribute__ ((__const__))
#endif

#ifndef _GLIBCXX_NORETURN
# define _GLIBCXX_NORETURN __attribute__ ((__noreturn__))
#endif

// See below for C++
#ifndef _GLIBCXX_NOTHROW
# ifndef __cplusplus
#  define _GLIBCXX_NOTHROW __attribute__((__nothrow__))
# endif
#endif

// Macros for visibility attributes.
//   _GLIBCXX_HAVE_ATTRIBUTE_VISIBILITY
//   _GLIBCXX_VISIBILITY
#define _GLIBCXX_HAVE_ATTRIBUTE_VISIBILITY

#if _GLIBCXX_HAVE_ATTRIBUTE_VISIBILITY
# define _GLIBCXX_VISIBILITY(V) __attribute__ ((__visibility__ (#V)))
#else
// If this is not supplied by the OS-specific or CPU-specific
// headers included below, it will be defined to an empty default.
# define _GLIBCXX_VISIBILITY(V) _GLIBCXX_PSEUDO_VISIBILITY(V)
#endif

// Macros for deprecated attributes.
//   _GLIBCXX_USE_DEPRECATED
//   _GLIBCXX_DEPRECATED
//   _GLIBCXX17_DEPRECATED
//   _GLIBCXX20_DEPRECATED( string-literal )
#ifndef _GLIBCXX_USE_DEPRECATED
# define _GLIBCXX_USE_DEPRECATED 1
#endif

#if defined(__DEPRECATED) && (__cplusplus >= 201103L)
# define _GLIBCXX_DEPRECATED __attribute__ ((__deprecated__))
#else
# define _GLIBCXX_DEPRECATED
#endif

#if defined(__DEPRECATED) && (__cplusplus >= 201703L)
# define _GLIBCXX17_DEPRECATED [[__deprecated__]]
#else
# define _GLIBCXX17_DEPRECATED
#endif

#if defined(__DEPRECATED) && (__cplusplus > 201703L)
# define _GLIBCXX20_DEPRECATED(MSG) [[deprecated(MSG)]]
#else
# define _GLIBCXX20_DEPRECATED(MSG)
#endif

// Macros for ABI tag attributes.
#ifndef _GLIBCXX_ABI_TAG_CXX11
# define _GLIBCXX_ABI_TAG_CXX11 __attribute ((__abi_tag__ ("cxx11")))
#endif

// Macro to warn about unused results.
#if __cplusplus >= 201703L
# define _GLIBCXX_NODISCARD [[__nodiscard__]]
#else
# define _GLIBCXX_NODISCARD
#endif



#if __cplusplus

// Macro for constexpr, to support in mixed 03/0x mode.
#ifndef _GLIBCXX_CONSTEXPR
# if __cplusplus >= 201103L
#  define _GLIBCXX_CONSTEXPR constexpr
#  define _GLIBCXX_USE_CONSTEXPR constexpr
# else
#  define _GLIBCXX_CONSTEXPR
#  define _GLIBCXX_USE_CONSTEXPR const
# endif
#endif

#ifndef _GLIBCXX14_CONSTEXPR
# if __cplusplus >= 201402L
#  define _GLIBCXX14_CONSTEXPR constexpr
# else
#  define _GLIBCXX14_CONSTEXPR
# endif
#endif

#ifndef _GLIBCXX17_CONSTEXPR
# if __cplusplus >= 201703L
#  define _GLIBCXX17_CONSTEXPR constexpr
# else
#  define _GLIBCXX17_CONSTEXPR
# endif
#endif

#ifndef _GLIBCXX20_CONSTEXPR
# if __cplusplus > 201703L
#  define _GLIBCXX20_CONSTEXPR constexpr
# else
#  define _GLIBCXX20_CONSTEXPR
# endif
#endif

#ifndef _GLIBCXX17_INLINE
# if __cplusplus >= 201703L
#  define _GLIBCXX17_INLINE inline
# else
#  define _GLIBCXX17_INLINE
# endif
#endif

// Macro for noexcept, to support in mixed 03/0x mode.
#ifndef _GLIBCXX_NOEXCEPT
# if __cplusplus >= 201103L
#  define _GLIBCXX_NOEXCEPT noexcept
#  define _GLIBCXX_NOEXCEPT_IF(...) noexcept(__VA_ARGS__)
#  define _GLIBCXX_USE_NOEXCEPT noexcept
#  define _GLIBCXX_THROW(_EXC)
# else
#  define _GLIBCXX_NOEXCEPT
#  define _GLIBCXX_NOEXCEPT_IF(...)
#  define _GLIBCXX_USE_NOEXCEPT throw()
#  define _GLIBCXX_THROW(_EXC) throw(_EXC)
# endif
#endif

#ifndef _GLIBCXX_NOTHROW
# define _GLIBCXX_NOTHROW _GLIBCXX_USE_NOEXCEPT
#endif

#ifndef _GLIBCXX_THROW_OR_ABORT
# if __cpp_exceptions
#  define _GLIBCXX_THROW_OR_ABORT(_EXC) (throw (_EXC))
# else
#  define _GLIBCXX_THROW_OR_ABORT(_EXC) (__builtin_abort())
# endif
#endif

#if __cpp_noexcept_function_type
#define _GLIBCXX_NOEXCEPT_PARM , bool _NE
#define _GLIBCXX_NOEXCEPT_QUAL noexcept (_NE)
#else
#define _GLIBCXX_NOEXCEPT_PARM
#define _GLIBCXX_NOEXCEPT_QUAL
#endif

// Macro for extern template, ie controlling template linkage via use
// of extern keyword on template declaration. As documented in the g++
// manual, it inhibits all implicit instantiations and is used
// throughout the library to avoid multiple weak definitions for
// required types that are already explicitly instantiated in the
// library binary. This substantially reduces the binary size of
// resulting executables.
// Special case: _GLIBCXX_EXTERN_TEMPLATE == -1 disallows extern
// templates only in basic_string, thus activating its debug-mode
// checks even at -O0.
#define _GLIBCXX_EXTERN_TEMPLATE

/*
  Outline of libstdc++ namespaces.

  namespace std
  {
    namespace __debug { }
    namespace __parallel { }
    namespace __cxx1998 { }

    namespace __detail {
      namespace __variant { }				// C++17
    }

    namespace rel_ops { }

    namespace tr1
    {
      namespace placeholders { }
      namespace regex_constants { }
      namespace __detail { }
    }

    namespace tr2 { }
    
    namespace decimal { }

    namespace chrono { }				// C++11
    namespace placeholders { }				// C++11
    namespace regex_constants { }			// C++11
    namespace this_thread { }				// C++11
    inline namespace literals {				// C++14
      inline namespace chrono_literals { }		// C++14
      inline namespace complex_literals { }		// C++14
      inline namespace string_literals { }		// C++14
      inline namespace string_view_literals { }		// C++17
    }
  }

  namespace abi { }

  namespace __gnu_cxx
  {
    namespace __detail { }
  }

  For full details see:
  http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/namespaces.html
*/
namespace std
{
  typedef __SIZE_TYPE__ 	size_t;
  typedef __PTRDIFF_TYPE__	ptrdiff_t;

#if __cplusplus >= 201103L
  typedef decltype(nullptr)	nullptr_t;
#endif
}

#define _GLIBCXX_USE_DUAL_ABI

#if ! _GLIBCXX_USE_DUAL_ABI
// Ignore any pre-defined value of _GLIBCXX_USE_CXX11_ABI
# undef _GLIBCXX_USE_CXX11_ABI
#endif

#ifndef _GLIBCXX_USE_CXX11_ABI
#define _GLIBCXX_USE_CXX11_ABI
#endif

#if _GLIBCXX_USE_CXX11_ABI
namespace std
{
  inline namespace __cxx11 __attribute__((__abi_tag__ ("cxx11"))) { }
}
namespace __gnu_cxx
{
  inline namespace __cxx11 __attribute__((__abi_tag__ ("cxx11"))) { }
}
# define _GLIBCXX_NAMESPACE_CXX11 __cxx11::
# define _GLIBCXX_BEGIN_NAMESPACE_CXX11 namespace __cxx11 {
# define _GLIBCXX_END_NAMESPACE_CXX11 }
# define _GLIBCXX_DEFAULT_ABI_TAG _GLIBCXX_ABI_TAG_CXX11
#else
# define _GLIBCXX_NAMESPACE_CXX11
# define _GLIBCXX_BEGIN_NAMESPACE_CXX11
# define _GLIBCXX_END_NAMESPACE_CXX11
# define _GLIBCXX_DEFAULT_ABI_TAG
#endif

// Defined if inline namespaces are used for versioning.
#define _GLIBCXX_INLINE_VERSION 

// Inline namespace for symbol versioning.
#if _GLIBCXX_INLINE_VERSION
# define _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace __8 {
# define _GLIBCXX_END_NAMESPACE_VERSION }

namespace std
{
inline _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus >= 201402L
  inline namespace literals {
    inline namespace chrono_literals { }
    inline namespace complex_literals { }
    inline namespace string_literals { }
#if __cplusplus > 201402L
    inline namespace string_view_literals { }
#endif // C++17
  }
#endif // C++14
_GLIBCXX_END_NAMESPACE_VERSION
}

namespace __gnu_cxx
{
inline _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_END_NAMESPACE_VERSION
}

#else
# define _GLIBCXX_BEGIN_NAMESPACE_VERSION
# define _GLIBCXX_END_NAMESPACE_VERSION
#endif

// Inline namespaces for special modes: debug, parallel.
#if defined(_GLIBCXX_DEBUG) || defined(_GLIBCXX_PARALLEL)
namespace std
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Non-inline namespace for components replaced by alternates in active mode.
  namespace __cxx1998
  {
# if _GLIBCXX_USE_CXX11_ABI
  inline namespace __cxx11 __attribute__((__abi_tag__ ("cxx11"))) { }
# endif
  }

_GLIBCXX_END_NAMESPACE_VERSION

  // Inline namespace for debug mode.
# ifdef _GLIBCXX_DEBUG
  inline namespace __debug { }
# endif

  // Inline namespaces for parallel mode.
# ifdef _GLIBCXX_PARALLEL
  inline namespace __parallel { }
# endif
}

// Check for invalid usage and unsupported mixed-mode use.
# if defined(_GLIBCXX_DEBUG) && defined(_GLIBCXX_PARALLEL)
#  error illegal use of multiple inlined namespaces
# endif

// Check for invalid use due to lack for weak symbols.
# if __NO_INLINE__ && !__GXX_WEAK__
#  warning currently using inlined namespace mode which may fail \
   without inlining due to lack of weak symbols
# endif
#endif

// Macros for namespace scope. Either namespace std:: or the name
// of some nested namespace within it corresponding to the active mode.
// _GLIBCXX_STD_A
// _GLIBCXX_STD_C
//
// Macros for opening/closing conditional namespaces.
// _GLIBCXX_BEGIN_NAMESPACE_ALGO
// _GLIBCXX_END_NAMESPACE_ALGO
// _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
// _GLIBCXX_END_NAMESPACE_CONTAINER
#if defined(_GLIBCXX_DEBUG)
# define _GLIBCXX_STD_C __cxx1998
# define _GLIBCXX_BEGIN_NAMESPACE_CONTAINER \
	 namespace _GLIBCXX_STD_C {
# define _GLIBCXX_END_NAMESPACE_CONTAINER }
#else
# define _GLIBCXX_STD_C std
# define _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
# define _GLIBCXX_END_NAMESPACE_CONTAINER
#endif

#ifdef _GLIBCXX_PARALLEL
# define _GLIBCXX_STD_A __cxx1998
# define _GLIBCXX_BEGIN_NAMESPACE_ALGO \
	 namespace _GLIBCXX_STD_A {
# define _GLIBCXX_END_NAMESPACE_ALGO }
#else
# define _GLIBCXX_STD_A std
# define _GLIBCXX_BEGIN_NAMESPACE_ALGO
# define _GLIBCXX_END_NAMESPACE_ALGO
#endif

// GLIBCXX_ABI Deprecated
// Define if compatibility should be provided for -mlong-double-64.
#undef _GLIBCXX_LONG_DOUBLE_COMPAT

// Inline namespace for long double 128 mode.
#if defined _GLIBCXX_LONG_DOUBLE_COMPAT && defined __LONG_DOUBLE_128__
namespace std
{
  inline namespace __gnu_cxx_ldbl128 { }
}
# define _GLIBCXX_NAMESPACE_LDBL __gnu_cxx_ldbl128::
# define _GLIBCXX_BEGIN_NAMESPACE_LDBL namespace __gnu_cxx_ldbl128 {
# define _GLIBCXX_END_NAMESPACE_LDBL }
#else
# define _GLIBCXX_NAMESPACE_LDBL
# define _GLIBCXX_BEGIN_NAMESPACE_LDBL
# define _GLIBCXX_END_NAMESPACE_LDBL
#endif
#if _GLIBCXX_USE_CXX11_ABI
# define _GLIBCXX_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_NAMESPACE_CXX11
# define _GLIBCXX_BEGIN_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_BEGIN_NAMESPACE_CXX11
# define _GLIBCXX_END_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_END_NAMESPACE_CXX11
#else
# define _GLIBCXX_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_NAMESPACE_LDBL
# define _GLIBCXX_BEGIN_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_BEGIN_NAMESPACE_LDBL
# define _GLIBCXX_END_NAMESPACE_LDBL_OR_CXX11 _GLIBCXX_END_NAMESPACE_LDBL
#endif

// Debug Mode implies checking assertions.
#if defined(_GLIBCXX_DEBUG) && !defined(_GLIBCXX_ASSERTIONS)
# define _GLIBCXX_ASSERTIONS 1
#endif

// Disable std::string explicit instantiation declarations in order to assert.
#ifdef _GLIBCXX_ASSERTIONS
# undef _GLIBCXX_EXTERN_TEMPLATE
# define _GLIBCXX_EXTERN_TEMPLATE -1
#endif

// Assert.
#if defined(_GLIBCXX_ASSERTIONS) \
  || defined(_GLIBCXX_PARALLEL) || defined(_GLIBCXX_PARALLEL_ASSERTIONS)
namespace std
{
  // Avoid the use of assert, because we're trying to keep the <cassert>
  // include out of the mix.
  extern "C++" inline void
  __replacement_assert(const char* __file, int __line,
		       const char* __function, const char* __condition)
  {
    __builtin_printf("%s:%d: %s: Assertion '%s' failed.\n", __file, __line,
		     __function, __condition);
    __builtin_abort();
  }
}
#define __glibcxx_assert_impl(_Condition)				 \
  do 									 \
  {							      		 \
    if (! (_Condition))                                                  \
      std::__replacement_assert(__FILE__, __LINE__, __PRETTY_FUNCTION__, \
				#_Condition);				 \
  } while (false)
#endif

#if defined(_GLIBCXX_ASSERTIONS)
# define __glibcxx_assert(_Condition) __glibcxx_assert_impl(_Condition)
#else
# define __glibcxx_assert(_Condition)
#endif

// Macros for race detectors.
// _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A) and
// _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A) should be used to explain
// atomic (lock-free) synchronization to race detectors:
// the race detector will infer a happens-before arc from the former to the
// latter when they share the same argument pointer.
//
// The most frequent use case for these macros (and the only case in the
// current implementation of the library) is atomic reference counting:
//   void _M_remove_reference()
//   {
//     _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&this->_M_refcount);
//     if (__gnu_cxx::__exchange_and_add_dispatch(&this->_M_refcount, -1) <= 0)
//       {
//         _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&this->_M_refcount);
//         _M_destroy(__a);
//       }
//   }
// The annotations in this example tell the race detector that all memory
// accesses occurred when the refcount was positive do not race with
// memory accesses which occurred after the refcount became zero.
#ifndef _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE
# define  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A)
#endif
#ifndef _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER
# define  _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A)
#endif

// Macros for C linkage: define extern "C" linkage only when using C++.
# define _GLIBCXX_BEGIN_EXTERN_C extern "C" {
# define _GLIBCXX_END_EXTERN_C }

#define _GLIBCXX_USE_ALLOCATOR_NEW

#else // !__cplusplus
# define _GLIBCXX_BEGIN_EXTERN_C
# define _GLIBCXX_END_EXTERN_C
#endif


// First includes.

// Pick up any OS-specific definitions.
#include <bits/os_defines.h>

// Pick up any CPU-specific definitions.
#include <bits/cpu_defines.h>

// If platform uses neither visibility nor psuedo-visibility,
// specify empty default for namespace annotation macros.
#ifndef _GLIBCXX_PSEUDO_VISIBILITY
# define _GLIBCXX_PSEUDO_VISIBILITY(V)
#endif

// Certain function definitions that are meant to be overridable from
// user code are decorated with this macro.  For some targets, this
// macro causes these definitions to be weak.
#ifndef _GLIBCXX_WEAK_DEFINITION
# define _GLIBCXX_WEAK_DEFINITION
#endif

// By default, we assume that __GXX_WEAK__ also means that there is support
// for declaring functions as weak while not defining such functions.  This
// allows for referring to functions provided by other libraries (e.g.,
// libitm) without depending on them if the respective features are not used.
#ifndef _GLIBCXX_USE_WEAK_REF
# define _GLIBCXX_USE_WEAK_REF __GXX_WEAK__
#endif

// Conditionally enable annotations for the Transactional Memory TS on C++11.
// Most of the following conditions are due to limitations in the current
// implementation.
#if __cplusplus >= 201103L && _GLIBCXX_USE_CXX11_ABI			\
  && _GLIBCXX_USE_DUAL_ABI && __cpp_transactional_memory >= 201500L	\
  &&  !_GLIBCXX_FULLY_DYNAMIC_STRING && _GLIBCXX_USE_WEAK_REF		\
  && _GLIBCXX_USE_ALLOCATOR_NEW
#define _GLIBCXX_TXN_SAFE transaction_safe
#define _GLIBCXX_TXN_SAFE_DYN transaction_safe_dynamic
#else
#define _GLIBCXX_TXN_SAFE
#define _GLIBCXX_TXN_SAFE_DYN
#endif

#if __cplusplus > 201402L
// In C++17 mathematical special functions are in namespace std.
# define _GLIBCXX_USE_STD_SPEC_FUNCS 1
#elif __cplusplus >= 201103L && __STDCPP_WANT_MATH_SPEC_FUNCS__ != 0
// For C++11 and C++14 they are in namespace std when requested.
# define _GLIBCXX_USE_STD_SPEC_FUNCS 1
#endif

// The remainder of the prewritten config is automatic; all the
// user hooks are listed above.

// Create a boolean flag to be used to determine if --fast-math is set.
#ifdef __FAST_MATH__
# define _GLIBCXX_FAST_MATH 1
#else
# define _GLIBCXX_FAST_MATH 0
#endif

// This marks string literals in header files to be extracted for eventual
// translation.  It is primarily used for messages in thrown exceptions; see
// src/functexcept.cc.  We use __N because the more traditional _N is used
// for something else under certain OSes (see BADNAMES).
#define __N(msgid)     (msgid)

// For example, <windows.h> is known to #define min and max as macros...
#undef min
#undef max

// N.B. these _GLIBCXX_USE_C99_XXX macros are defined unconditionally
// so they should be tested with #if not with #ifdef.
#if __cplusplus >= 201103L
# ifndef _GLIBCXX_USE_C99_MATH
#  define _GLIBCXX_USE_C99_MATH _GLIBCXX11_USE_C99_MATH
# endif
# ifndef _GLIBCXX_USE_C99_COMPLEX
# define _GLIBCXX_USE_C99_COMPLEX _GLIBCXX11_USE_C99_COMPLEX
# endif
# ifndef _GLIBCXX_USE_C99_STDIO
# define _GLIBCXX_USE_C99_STDIO _GLIBCXX11_USE_C99_STDIO
# endif
# ifndef _GLIBCXX_USE_C99_STDLIB
# define _GLIBCXX_USE_C99_STDLIB _GLIBCXX11_USE_C99_STDLIB
# endif
# ifndef _GLIBCXX_USE_C99_WCHAR
# define _GLIBCXX_USE_C99_WCHAR _GLIBCXX11_USE_C99_WCHAR
# endif
#else
# ifndef _GLIBCXX_USE_C99_MATH
#  define _GLIBCXX_USE_C99_MATH _GLIBCXX98_USE_C99_MATH
# endif
# ifndef _GLIBCXX_USE_C99_COMPLEX
# define _GLIBCXX_USE_C99_COMPLEX _GLIBCXX98_USE_C99_COMPLEX
# endif
# ifndef _GLIBCXX_USE_C99_STDIO
# define _GLIBCXX_USE_C99_STDIO _GLIBCXX98_USE_C99_STDIO
# endif
# ifndef _GLIBCXX_USE_C99_STDLIB
# define _GLIBCXX_USE_C99_STDLIB _GLIBCXX98_USE_C99_STDLIB
# endif
# ifndef _GLIBCXX_USE_C99_WCHAR
# define _GLIBCXX_USE_C99_WCHAR _GLIBCXX98_USE_C99_WCHAR
# endif
#endif

// Unless explicitly specified, enable char8_t extensions only if the core
// language char8_t feature macro is defined.
#ifndef _GLIBCXX_USE_CHAR8_T
# ifdef __cpp_char8_t
#  define _GLIBCXX_USE_CHAR8_T 1
# endif
#endif
#ifdef _GLIBCXX_USE_CHAR8_T
# define __cpp_lib_char8_t 201907L
#endif

/* Define if __float128 is supported on this host. */
#if defined(__FLOAT128__) || defined(__SIZEOF_FLOAT128__)
#define _GLIBCXX_USE_FLOAT128
#endif

#if __GNUC__ >= 7
// Assume these are available if the compiler claims to be a recent GCC:
# define _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP 1
# define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
# define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
# define _GLIBCXX_BUILTIN_IS_SAME_AS(T, U) __is_same_as(T, U)
# if __GNUC__ >= 9
#  define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1
# endif
#elif defined(__is_identifier) && defined(__has_builtin)
// For non-GNU compilers:
# if ! __is_identifier(__has_unique_object_representations)
#  define _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP 1
# endif
# if ! __is_identifier(__is_aggregate)
#  define _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE 1
# endif
# if __has_builtin(__builtin_launder)
#  define _GLIBCXX_HAVE_BUILTIN_LAUNDER 1
# endif
# if __has_builtin(__builtin_is_constant_evaluated)
#  define _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED 1
# endif
# if ! __is_identifier(__is_same)
#  define _GLIBCXX_BUILTIN_IS_SAME_AS(T, U) __is_same(T, U)
# endif
#endif // GCC

// PSTL configuration

#if __cplusplus >= 201703L
// This header is not installed for freestanding:
#if __has_include(<pstl/pstl_config.h>)
// Preserved here so we have some idea which version of upstream we've pulled in
// #define PSTL_VERSION 9000

// For now this defaults to being based on the presence of Thread Building Blocks
# ifndef _GLIBCXX_USE_TBB_PAR_BACKEND
#  define _GLIBCXX_USE_TBB_PAR_BACKEND __has_include(<tbb/tbb.h>)
# endif
// This section will need some rework when a new (default) backend type is added
# if _GLIBCXX_USE_TBB_PAR_BACKEND
#  define _PSTL_PAR_BACKEND_TBB
# else
#  define _PSTL_PAR_BACKEND_SERIAL
# endif

# define _PSTL_ASSERT(_Condition) __glibcxx_assert(_Condition)
# define _PSTL_ASSERT_MSG(_Condition, _Message) __glibcxx_assert(_Condition)

#include <pstl/pstl_config.h>
#endif // __has_include
#endif // C++17

// End of prewritten config; the settings discovered at configure time follow.