Marek Polacek
9a15d3beac
This patch implements C++23 P2255R2, which adds two new type traits to
detect reference binding to a temporary. They can be used to detect code
like
std::tuple<const std::string&> t("meow");
which is incorrect because it always creates a dangling reference, because
the std::string temporary is created inside the selected constructor of
std::tuple, and not outside it.
There are two new compiler builtins, __reference_constructs_from_temporary
and __reference_converts_from_temporary. The former is used to simulate
direct- and the latter copy-initialization context. But I had a hard time
finding a test where there's actually a difference. Under DR 2267, both
of these are invalid:
struct A { } a;
struct B { explicit B(const A&); };
const B &b1{a};
const B &b2(a);
so I had to peruse [over.match.ref], and eventually realized that the
difference can be seen here:
struct G {
operator int(); // #1
explicit operator int&&(); // #2
};
int&& r1(G{}); // use #2 (no temporary)
int&& r2 = G{}; // use #1 (a temporary is created to be bound to int&&)
The implementation itself was rather straightforward because we already
have the conv_binds_ref_to_prvalue function. The main function here is
ref_xes_from_temporary.
I've changed the return type of ref_conv_binds_directly to tristate, because
previously the function didn't distinguish between an invalid conversion and
one that binds to a prvalue. Since it no longer returns a bool, I removed
the _p suffix.
The patch also adds the relevant class and variable templates to <type_traits>.
PR c++/104477
gcc/c-family/ChangeLog:
* c-common.cc (c_common_reswords): Add
__reference_constructs_from_temporary and
__reference_converts_from_temporary.
* c-common.h (enum rid): Add RID_REF_CONSTRUCTS_FROM_TEMPORARY and
RID_REF_CONVERTS_FROM_TEMPORARY.
gcc/cp/ChangeLog:
* call.cc (ref_conv_binds_directly_p): Rename to ...
(ref_conv_binds_directly): ... this. Add a new bool parameter. Change
the return type to tristate.
* constraint.cc (diagnose_trait_expr): Handle
CPTK_REF_CONSTRUCTS_FROM_TEMPORARY and CPTK_REF_CONVERTS_FROM_TEMPORARY.
* cp-tree.h: Include "tristate.h".
(enum cp_trait_kind): Add CPTK_REF_CONSTRUCTS_FROM_TEMPORARY
and CPTK_REF_CONVERTS_FROM_TEMPORARY.
(ref_conv_binds_directly_p): Rename to ...
(ref_conv_binds_directly): ... this.
(ref_xes_from_temporary): Declare.
* cxx-pretty-print.cc (pp_cxx_trait_expression): Handle
CPTK_REF_CONSTRUCTS_FROM_TEMPORARY and CPTK_REF_CONVERTS_FROM_TEMPORARY.
* method.cc (ref_xes_from_temporary): New.
* parser.cc (cp_parser_primary_expression): Handle
RID_REF_CONSTRUCTS_FROM_TEMPORARY and RID_REF_CONVERTS_FROM_TEMPORARY.
(cp_parser_trait_expr): Likewise.
(warn_for_range_copy): Adjust to call ref_conv_binds_directly.
* semantics.cc (trait_expr_value): Handle
CPTK_REF_CONSTRUCTS_FROM_TEMPORARY and CPTK_REF_CONVERTS_FROM_TEMPORARY.
(finish_trait_expr): Likewise.
libstdc++-v3/ChangeLog:
* include/std/type_traits (reference_constructs_from_temporary,
reference_converts_from_temporary): New class templates.
(reference_constructs_from_temporary_v,
reference_converts_from_temporary_v): New variable templates.
(__cpp_lib_reference_from_temporary): Define for C++23.
* include/std/version (__cpp_lib_reference_from_temporary): Define for
C++23.
* testsuite/20_util/variable_templates_for_traits.cc: Test
reference_constructs_from_temporary_v and
reference_converts_from_temporary_v.
* testsuite/20_util/reference_from_temporary/value.cc: New test.
* testsuite/20_util/reference_from_temporary/value2.cc: New test.
* testsuite/20_util/reference_from_temporary/version.cc: New test.
gcc/testsuite/ChangeLog:
* g++.dg/ext/reference_constructs_from_temporary1.C: New test.
* g++.dg/ext/reference_converts_from_temporary1.C: New test.
346 lines
11 KiB
C++
346 lines
11 KiB
C++
// -*- C++ -*- Libstdc++ version details header.
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// Copyright (C) 2018-2022 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file version
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* This is a Standard C++ Library file. You should @c \#include this file
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* in your programs, rather than any of the @a *.h implementation files.
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*/
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#ifndef _GLIBCXX_VERSION_INCLUDED
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#define _GLIBCXX_VERSION_INCLUDED
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#pragma GCC system_header
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#include <bits/c++config.h>
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// c++03
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#if _GLIBCXX_HOSTED
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# define __cpp_lib_incomplete_container_elements 201505L
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#endif
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#if !defined(__STRICT_ANSI__)
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// gnu++03
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# define __cpp_lib_uncaught_exceptions 201411L
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#endif
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#if __cplusplus >= 201103L
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// c++11
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#define __cpp_lib_is_null_pointer 201309L
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#define __cpp_lib_result_of_sfinae 201210L
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#if _GLIBCXX_HOSTED
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# define __cpp_lib_allocator_traits_is_always_equal 201411L
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#if __cplusplus <= 201703L // N.B. updated value in C++20
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# define __cpp_lib_shared_ptr_arrays 201611L
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#endif
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#endif
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#if !defined(__STRICT_ANSI__)
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// gnu++11
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# define __cpp_lib_is_swappable 201603L
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# define __cpp_lib_void_t 201411L
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# if _GLIBCXX_HOSTED
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# define __cpp_lib_enable_shared_from_this 201603L
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# endif
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#endif
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// For C++11 and later we support ISO/IEC 29124 Mathematical Special Functions
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#define __STDCPP_MATH_SPEC_FUNCS__ 201003L
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#if __cplusplus >= 201402L
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// c++14
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#if __cpp_impl_coroutine
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# define __cpp_lib_coroutine 201902L
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#endif
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#define __cpp_lib_integral_constant_callable 201304L
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#define __cpp_lib_is_final 201402L
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#define __cpp_lib_transformation_trait_aliases 201304L
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#if _GLIBCXX_HOSTED
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# define __cpp_lib_chrono_udls 201304L
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# define __cpp_lib_complex_udls 201309L
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# define __cpp_lib_exchange_function 201304L
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# define __cpp_lib_generic_associative_lookup 201304L
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# define __cpp_lib_integer_sequence 201304L
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# define __cpp_lib_make_reverse_iterator 201402L
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# define __cpp_lib_make_unique 201304L
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# ifndef _GLIBCXX_DEBUG // PR libstdc++/70303
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# define __cpp_lib_null_iterators 201304L
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# endif
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# define __cpp_lib_quoted_string_io 201304L
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# define __cpp_lib_robust_nonmodifying_seq_ops 201304L
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# ifdef _GLIBCXX_HAS_GTHREADS
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# define __cpp_lib_shared_timed_mutex 201402L
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# endif
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# define __cpp_lib_string_udls 201304L
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# define __cpp_lib_transparent_operators 201510L
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# define __cpp_lib_tuple_element_t 201402L
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# define __cpp_lib_tuples_by_type 201304L
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#endif
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#if __cplusplus >= 201703L
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// c++17
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#define __cpp_lib_addressof_constexpr 201603L
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#define __cpp_lib_atomic_is_always_lock_free 201603L
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#define __cpp_lib_bool_constant 201505L
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#define __cpp_lib_byte 201603L
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#ifdef _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP
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# define __cpp_lib_has_unique_object_representations 201606L
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#endif
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#ifdef __GCC_DESTRUCTIVE_SIZE
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# define __cpp_lib_hardware_interference_size 201703L
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#endif
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#ifdef _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE
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# define __cpp_lib_is_aggregate 201703L
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#endif
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#define __cpp_lib_is_invocable 201703L
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#define __cpp_lib_is_swappable 201603L
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#ifdef _GLIBCXX_HAVE_BUILTIN_LAUNDER
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# define __cpp_lib_launder 201606L
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#endif
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#define __cpp_lib_logical_traits 201510L
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#define __cpp_lib_type_trait_variable_templates 201510L
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#define __cpp_lib_uncaught_exceptions 201411L
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#define __cpp_lib_void_t 201411L
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#if _GLIBCXX_HOSTED
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#define __cpp_lib_any 201606L
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#define __cpp_lib_apply 201603L
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#if __cplusplus == 201703L // N.B. updated value in C++20
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# define __cpp_lib_array_constexpr 201803L
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#endif
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#define __cpp_lib_as_const 201510L
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#define __cpp_lib_boyer_moore_searcher 201603L
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#define __cpp_lib_chrono 201611L
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#define __cpp_lib_clamp 201603L
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#if __cplusplus == 201703L // N.B. updated value in C++20
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# if _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
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# define __cpp_lib_constexpr_char_traits 201611L
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# define __cpp_lib_constexpr_string 201611L
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# endif
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#endif
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#define __cpp_lib_enable_shared_from_this 201603L
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#define __cpp_lib_execution 201902L // FIXME: should be 201603L
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#define __cpp_lib_filesystem 201703L
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#define __cpp_lib_gcd 201606L
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#define __cpp_lib_gcd_lcm 201606L
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#define __cpp_lib_hypot 201603L
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#define __cpp_lib_invoke 201411L
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#define __cpp_lib_lcm 201606L
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#define __cpp_lib_make_from_tuple 201606L
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#define __cpp_lib_map_try_emplace 201411L
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#define __cpp_lib_math_special_functions 201603L
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#ifdef _GLIBCXX_HAS_GTHREADS
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# define __cpp_lib_memory_resource 201603L
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#else
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# define __cpp_lib_memory_resource 1
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#endif
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#define __cpp_lib_node_extract 201606L
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#define __cpp_lib_nonmember_container_access 201411L
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#define __cpp_lib_not_fn 201603L
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#if __cplusplus == 201703L // N.B. updated value in C++20
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# define __cpp_lib_optional 201606L
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#endif
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#define __cpp_lib_parallel_algorithm 201603L
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#define __cpp_lib_raw_memory_algorithms 201606L
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#define __cpp_lib_sample 201603L
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#ifdef _GLIBCXX_HAS_GTHREADS
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# define __cpp_lib_scoped_lock 201703L
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# define __cpp_lib_shared_mutex 201505L
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#endif
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#define __cpp_lib_shared_ptr_weak_type 201606L
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#define __cpp_lib_string_view 201803L
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#if _GLIBCXX_FLOAT_IS_IEEE_BINARY32 && _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 \
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&& __SIZE_WIDTH__ >= 32
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# define __cpp_lib_to_chars 201611L
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#endif
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#define __cpp_lib_unordered_map_try_emplace 201411L
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#if !(__cpp_concepts >= 202002L && __cpp_constexpr >= 201811L)
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// N.B. updated value in C++20
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# define __cpp_lib_variant 202102L
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#endif
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#endif
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#if __cplusplus >= 202002L
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// c++20
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#define __cpp_lib_atomic_flag_test 201907L
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#define __cpp_lib_atomic_float 201711L
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#define __cpp_lib_atomic_ref 201806L
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#define __cpp_lib_atomic_value_initialization 201911L
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#if __has_builtin(__builtin_bit_cast)
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# define __cpp_lib_bit_cast 201806L
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#endif
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#define __cpp_lib_bitops 201907L
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#define __cpp_lib_bounded_array_traits 201902L
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// __cpp_lib_char8_t is defined in <bits/c++config.h>
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#if __cpp_concepts >= 201907L
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# define __cpp_lib_concepts 202002L
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#endif
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#if __cpp_impl_destroying_delete
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# define __cpp_lib_destroying_delete 201806L
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#endif
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#define __cpp_lib_endian 201907L
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#define __cpp_lib_int_pow2 202002L
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#ifdef _GLIBCXX_HAVE_IS_CONSTANT_EVALUATED
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# define __cpp_lib_is_constant_evaluated 201811L
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#endif
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#if __has_builtin(__is_layout_compatible) \
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&& __has_builtin(__builtin_is_corresponding_member)
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# define __cpp_lib_is_layout_compatible 201907L
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#endif
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#define __cpp_lib_is_nothrow_convertible 201806L
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#if __has_builtin(__is_pointer_interconvertible_base_of) \
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&& __has_builtin(__builtin_is_pointer_interconvertible_with_class)
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# define __cpp_lib_is_pointer_interconvertible 201907L
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#endif
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#define __cpp_lib_remove_cvref 201711L
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#if __has_builtin(__builtin_source_location)
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# define __cpp_lib_source_location 201907L
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#endif
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#if __cpp_impl_three_way_comparison >= 201907L && __cpp_lib_concepts
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# define __cpp_lib_three_way_comparison 201907L
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#endif
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#define __cpp_lib_type_identity 201806L
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#define __cpp_lib_unwrap_ref 201811L
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#if _GLIBCXX_HOSTED
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#define __cpp_lib_array_constexpr 201811L
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#define __cpp_lib_assume_aligned 201811L
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#define __cpp_lib_atomic_shared_ptr 201711L
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#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
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# define __cpp_lib_atomic_wait 201907L
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# if __cpp_aligned_new
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# define __cpp_lib_barrier 201907L
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# endif
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#endif
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#define __cpp_lib_bind_front 201907L
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// FIXME: #define __cpp_lib_execution 201902L
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#define __cpp_lib_integer_comparison_functions 202002L
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#define __cpp_lib_constexpr_algorithms 201806L
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#ifdef __cpp_lib_is_constant_evaluated
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# define __cpp_lib_constexpr_char_traits 201811L
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#endif
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#define __cpp_lib_constexpr_complex 201711L
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#define __cpp_lib_constexpr_dynamic_alloc 201907L
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#define __cpp_lib_constexpr_functional 201907L
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#define __cpp_lib_constexpr_iterator 201811L
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#define __cpp_lib_constexpr_memory 201811L
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#define __cpp_lib_constexpr_numeric 201911L
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#ifdef __cpp_lib_is_constant_evaluated
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# if _GLIBCXX_USE_CXX11_ABI
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# define __cpp_lib_constexpr_string 201907L
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# else
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# define __cpp_lib_constexpr_string 201811L
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# endif
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#endif
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#define __cpp_lib_constexpr_string_view 201811L
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#define __cpp_lib_constexpr_tuple 201811L
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#define __cpp_lib_constexpr_utility 201811L
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#define __cpp_lib_constexpr_vector 201907L
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#define __cpp_lib_erase_if 202002L
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#define __cpp_lib_generic_unordered_lookup 201811L
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#define __cpp_lib_interpolate 201902L
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#ifdef _GLIBCXX_HAS_GTHREADS
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# define __cpp_lib_jthread 201911L
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#endif
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#if __cpp_lib_atomic_wait
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# define __cpp_lib_latch 201907L
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#endif
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#define __cpp_lib_list_remove_return_type 201806L
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#if __cpp_lib_concepts
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# define __cpp_lib_make_obj_using_allocator 201811L
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#endif
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#define __cpp_lib_math_constants 201907L
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#define __cpp_lib_optional 202106L
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#define __cpp_lib_polymorphic_allocator 201902L
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#if __cpp_lib_concepts
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# define __cpp_lib_ranges 202110L
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#endif
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#if __cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
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# define __cpp_lib_semaphore 201907L
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#endif
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#define __cpp_lib_shared_ptr_arrays 201707L
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#define __cpp_lib_shift 201806L
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#define __cpp_lib_smart_ptr_for_overwrite 202002L
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#if __cpp_lib_concepts
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# define __cpp_lib_span 202002L
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#endif
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#define __cpp_lib_ssize 201902L
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#define __cpp_lib_starts_ends_with 201711L
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# if _GLIBCXX_USE_CXX11_ABI
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// Only supported with cxx11-abi
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# define __cpp_lib_syncbuf 201803L
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# endif
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#define __cpp_lib_to_address 201711L
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#define __cpp_lib_to_array 201907L
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#if __cpp_concepts >= 202002L && __cpp_constexpr >= 201811L
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# define __cpp_lib_variant 202106L
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#endif
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#endif
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#if __cplusplus > 202002L
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// c++23
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#define __cpp_lib_byteswap 202110L
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#define __cpp_lib_constexpr_typeinfo 202106L
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#define __cpp_lib_is_scoped_enum 202011L
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#define __cpp_lib_reference_from_temporary 202202L
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#if _GLIBCXX_HOSTED
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#define __cpp_lib_adaptor_iterator_pair_constructor 202106L
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#if __cpp_constexpr_dynamic_alloc
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# undef __cpp_lib_constexpr_memory
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# define __cpp_lib_constexpr_memory 202202L
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#endif
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#if __cpp_concepts >= 202002L
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# define __cpp_lib_expected 202202L
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#endif
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#define __cpp_lib_invoke_r 202106L
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#define __cpp_lib_ios_noreplace 202200L
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#if __cpp_lib_concepts
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# undef __cpp_lib_optional
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# define __cpp_lib_optional 202110L
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#endif
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#define __cpp_lib_move_only_function 202110L
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#if __cpp_lib_span
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# define __cpp_lib_spanstream 202106L
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#endif
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#if _GLIBCXX_HAVE_STACKTRACE
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# define __cpp_lib_stacktrace 202011L
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#endif
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#define __cpp_lib_stdatomic_h 202011L
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#define __cpp_lib_string_contains 202011L
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#if _GLIBCXX_USE_CXX11_ABI // Only supported with cxx11-abi
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# define __cpp_lib_string_resize_and_overwrite 202110L
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#endif
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#define __cpp_lib_to_underlying 202102L
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#define __cpp_lib_unreachable 202202L
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#endif
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#endif // C++23
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#endif // C++20
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#endif // C++17
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#endif // C++14
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#endif // C++11
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#endif // _GLIBCXX_VERSION_INCLUDED
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