Library feature-test macros(since C++20)

From cppreference.com

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

[edit]

Utilities library

Language support

Type support (basic types, RTTI)

Library feature-test macros(C++20)

Program utilities

Variadic functions

initializer_list

(C++11)

is_constant_evaluated

(C++20)

is_within_lifetime

(C++26)

source_location

(C++20)

Coroutine support(C++20)

Contract support(C++26)

Three-way comparison

three_way_comparablethree_way_comparable_with

(C++20)(C++20)

strong_ordering

(C++20)

weak_ordering

(C++20)

partial_ordering

(C++20)

common_comparison_category

(C++20)

compare_three_way_result

(C++20)

(C++20)

(C++20)

(C++20)

(C++20)

compare_strong_order_fallback

(C++20)

compare_weak_order_fallback

(C++20)

compare_partial_order_fallback

(C++20)

is_eqis_ltis_lteq

(C++20)(C++20)(C++20)

is_neqis_gtis_gteq

(C++20)(C++20)(C++20)

General utilities

Function objects
Bit manipulation(C++20)
C-style bit manipulation(C++26)
bitset
hash (C++11)

Relational operators(deprecated in C++20)

rel_ops::operator!=rel_ops::operator>

rel_ops::operator<=rel_ops::operator>=

Integer comparison functions

cmp_equalcmp_lesscmp_less_than

(C++20)(C++20)(C++20)

cmp_not_equalcmp_greatercmp_greater_than

(C++20)(C++20)(C++20)

in_range

(C++20)

Swap andtype operations

swap
ranges::swap (C++20)
exchange (C++14)
declval (C++11)
to_underlying (C++23)

forward (C++11)
forward_like (C++23)
move (C++11)
move_if_noexcept (C++11)
as_const (C++17)

Common vocabulary types

pair
tuple (C++11)
optional (C++17)
any (C++17)
variant (C++17)

tuple_size (C++11)
tuple_element (C++11)
apply (C++17)
make_from_tuple (C++17)
expected (C++23)

[edit]

Each of following macros is defined if the header<version> or one of the corresponding headers specified in the table is included.

[edit]

Macro name	Value	Header	Free- standing
`__cpp_lib_adaptor_iterator_pair_constructor`	202106L	`<stack><queue>`
`__cpp_lib_addressof_constexpr`	201603L	`<memory>`	Yes
`__cpp_lib_algorithm_default_value_type`	202403L	`<algorithm><ranges><string><deque><list><forward_list><vector>`
`__cpp_lib_algorithm_iterator_requirements`	202207L	`<algorithm><numeric><memory>`
`__cpp_lib_aligned_accessor`	202411L	`<mdspan>`
`__cpp_lib_allocate_at_least`	202302L	`<memory>`
`__cpp_lib_allocator_traits_is_always_equal`	201411L	`<memory><scoped_allocator><string><deque><forward_list><list><vector><map><set><unordered_map><unordered_set>`	Yes
`__cpp_lib_any`	201606L	`<any>`
`__cpp_lib_apply`	201603L	`<tuple>`	Yes
`__cpp_lib_array_constexpr`	201811L	`<iterator><array>`
`__cpp_lib_as_const`	201510L	`<utility>`	Yes
`__cpp_lib_associative_heterogeneous_erasure`	202110L	`<map><set><unordered_map><unordered_set>`
`__cpp_lib_associative_heterogeneous_insertion`	202306L	`<map><set><unordered_map><unordered_set>`
`__cpp_lib_assume_aligned`	201811L	`<memory>`	Yes
`__cpp_lib_atomic_flag_test`	201907L	`<atomic>`	Yes
`__cpp_lib_atomic_float`	201711L	`<atomic>`	Yes
`__cpp_lib_atomic_is_always_lock_free`	201603L	`<atomic>`	Yes
`__cpp_lib_atomic_lock_free_type_aliases`	201907L	`<atomic>`
`__cpp_lib_atomic_min_max`	202403L	`<atomic>`	Yes
`__cpp_lib_atomic_ref`	202411L	`<atomic>`	Yes
`__cpp_lib_atomic_shared_ptr`	201711L	`<memory>`
`__cpp_lib_atomic_value_initialization`	201911L	`<atomic><memory>`	Yes
`__cpp_lib_atomic_wait`	201907L	`<atomic>`	Yes
`__cpp_lib_barrier`	202302L	`<barrier>`
`__cpp_lib_bind_back`	202306L	`<functional>`	Yes
`__cpp_lib_bind_front`	202306L	`<functional>`	Yes
`__cpp_lib_bit_cast`	201806L	`<bit>`	Yes
`__cpp_lib_bitops`	201907L	`<bit>`	Yes
`__cpp_lib_bitset`	202306L	`<bitset>`
`__cpp_lib_bool_constant`	201505L	`<type_traits>`	Yes
`__cpp_lib_bounded_array_traits`	201902L	`<type_traits>`	Yes
`__cpp_lib_boyer_moore_searcher`	201603L	`<functional>`
`__cpp_lib_byte`	201603L	`<cstddef>`	Yes
`__cpp_lib_byteswap`	202110L	`<bit>`	Yes
`__cpp_lib_char8_t`	201907L	`<atomic><filesystem><istream><limits><locale><ostream><string><string_view>`	Yes
`__cpp_lib_chrono`	202306L	`<chrono>`
`__cpp_lib_chrono_udls`	201304L	`<chrono>`
`__cpp_lib_clamp`	201603L	`<algorithm>`
`__cpp_lib_common_reference`	202302L	`<type_traits>`	Yes
`__cpp_lib_common_reference_wrapper`	202302L	`<functional>`	Yes
`__cpp_lib_complex_udls`	201309L	`<complex>`
`__cpp_lib_concepts`	202207L	`<concepts><compare>`	Yes
`__cpp_lib_constexpr_algorithms`	202306L	`<algorithm><utility>`
`__cpp_lib_constexpr_atomic`	202411L	`<atomic>`
`__cpp_lib_constexpr_bitset`	202207L	`<bitset>`
`__cpp_lib_constexpr_charconv`	202207L	`<charconv>`	Yes
`__cpp_lib_constexpr_cmath`	202306L	`<cmath><cstdlib>`
`__cpp_lib_constexpr_complex`	202306L	`<complex>`
`__cpp_lib_constexpr_deque`	202502L	`<deque>`
`__cpp_lib_constexpr_dynamic_alloc`	201907L	`<memory>`
`__cpp_lib_constexpr_exceptions`	202502L	`<exception><stdexcept><expected><optional><variant><format>`
`__cpp_lib_constexpr_flat_map`	202502L	`<flat_map>`
`__cpp_lib_constexpr_flat_set`	202502L	`<flat_set>`
`__cpp_lib_constexpr_forward_list`	202502L	`<forward_list>`
`__cpp_lib_constexpr_functional`	201907L	`<functional>`	Yes
`__cpp_lib_constexpr_inplace_vector`	202502L	`<inplace_vector>`
`__cpp_lib_constexpr_iterator`	201811L	`<iterator>`	Yes
`__cpp_lib_constexpr_list`	202502L	`<list>`
`__cpp_lib_constexpr_map`	202502L	`<map>`
`__cpp_lib_constexpr_memory`	202202L	`<memory>`	Yes
`__cpp_lib_constexpr_new`	202406L	`<new>`	Yes
`__cpp_lib_constexpr_numeric`	201911L	`<numeric>`
`__cpp_lib_constexpr_queue`	202502L	`<queue>`
`__cpp_lib_constexpr_set`	202502L	`<set>`
`__cpp_lib_constexpr_stack`	202502L	`<stack>`
`__cpp_lib_constexpr_string`	201907L	`<string>`
`__cpp_lib_constexpr_string_view`	201811L	`<string_view>`
`__cpp_lib_constexpr_tuple`	201811L	`<tuple>`	Yes
`__cpp_lib_constexpr_typeinfo`	202106L	`<typeinfo>`	Yes
`__cpp_lib_constexpr_unordered_map`	202502L	`<unordered_map>`
`__cpp_lib_constexpr_unordered_set`	202502L	`<unordered_set>`
`__cpp_lib_constexpr_utility`	201811L	`<utility>`	Yes
`__cpp_lib_constexpr_vector`	201907L	`<vector>`
`__cpp_lib_constrained_equality`	202411L	`<utility><tuple><optional><variant><expected>`	Yes
`__cpp_lib_containers_ranges`	202202L	`<vector><list><forward_list><map><set><unordered_map><unordered_set><deque><queue><stack><string>`
`__cpp_lib_contracts`	202502L	`<contracts>`	Yes
`__cpp_lib_copyable_function`	202306L	`<functional>`
`__cpp_lib_coroutine`	201902L	`<coroutine>`	Yes
`__cpp_lib_debugging`	202403L	`<debugging>`	Yes
`__cpp_lib_destroying_delete`	201806L	`<new>`	Yes
`__cpp_lib_enable_shared_from_this`	201603L	`<memory>`
`__cpp_lib_endian`	201907L	`<bit>`	Yes
`__cpp_lib_erase_if`	202002L	`<string><deque><forward_list><list><vector><map><set><unordered_map><unordered_set>`
`__cpp_lib_exchange_function`	201304L	`<utility>`	Yes
`__cpp_lib_execution`	201902L	`<execution>`
`__cpp_lib_expected`	202211L	`<expected>`
`__cpp_lib_filesystem`	201703L	`<filesystem>`
`__cpp_lib_flat_map`	202207L	`<flat_map>`
`__cpp_lib_flat_set`	202207L	`<flat_set>`
`__cpp_lib_format`	202311L	`<format>`
`__cpp_lib_format_ranges`	202207L	`<format>`
`__cpp_lib_format_path`	202403L	`<filesystem>`
`__cpp_lib_format_uchar`	202311L	`<format>`
`__cpp_lib_formatters`	202302L	`<stacktrace><thread>`
`__cpp_lib_forward_like`	202207L	`<utility>`	Yes
`__cpp_lib_freestanding_algorithm`	202502L	`<algorithm>`	Yes
`__cpp_lib_freestanding_array`	202311L	`<array>`	Yes
`__cpp_lib_freestanding_char_traits`	202306L	`<string>`	Yes
`__cpp_lib_freestanding_charconv`	202306L	`<charconv>`	Yes
`__cpp_lib_freestanding_cstdlib`	202306L	`<cstdlib><cmath>`	Yes
`__cpp_lib_freestanding_cstring`	202311L	`<cstring>`	Yes
`__cpp_lib_freestanding_cwchar`	202306L	`<cwchar>`	Yes
`__cpp_lib_freestanding_errc`	202306L	`<cerrno><system_error>`	Yes
`__cpp_lib_freestanding_execution`	202502L	`<execution>`	Yes
`__cpp_lib_freestanding_expected`	202311L	`<expected>`	Yes
`__cpp_lib_freestanding_feature_test_macros`	202306L		Yes
`__cpp_lib_freestanding_functional`	202306L	`<functional>`	Yes
`__cpp_lib_freestanding_iterator`	202306L	`<iterator>`	Yes
`__cpp_lib_freestanding_mdspan`	202311L	`<mdspan>`	Yes
`__cpp_lib_freestanding_memory`	202502L	`<memory>`	Yes
`__cpp_lib_freestanding_numeric`	202502L	`<numeric>`	Yes
`__cpp_lib_freestanding_operator_new`	202306L		Yes
`__cpp_lib_freestanding_optional`	202311L	`<optional>`	Yes
`__cpp_lib_freestanding_random`	202502L	`<random>`	Yes
`__cpp_lib_freestanding_ranges`	202306L	`<ranges>`	Yes
`__cpp_lib_freestanding_ratio`	202306L	`<ratio>`	Yes
`__cpp_lib_freestanding_string_view`	202311L	`<string_view>`	Yes
`__cpp_lib_freestanding_tuple`	202306L	`<tuple>`	Yes
`__cpp_lib_freestanding_utility`	202306L	`<utility>`	Yes
`__cpp_lib_freestanding_variant`	202311L	`<variant>`	Yes
`__cpp_lib_fstream_native_handle`	202306L	`<fstream>`
`__cpp_lib_function_ref`	202306L	`<functional>`
`__cpp_lib_gcd_lcm`	201606L	`<numeric>`
`__cpp_lib_generator`	202207L	`<generator>`
`__cpp_lib_generic_associative_lookup`	201304L	`<map><set>`
`__cpp_lib_generic_unordered_lookup`	201811L	`<unordered_map><unordered_set>`
`__cpp_lib_hardware_interference_size`	201703L	`<new>`	Yes
`__cpp_lib_has_unique_object_representations`	201606L	`<type_traits>`	Yes
`__cpp_lib_hazard_pointer`	202306L	`<hazard_pointer>`
`__cpp_lib_hive`	202502L	`<hive>`
`__cpp_lib_hypot`	201603L	`<cmath>`
`__cpp_lib_incomplete_container_elements`	201505L	`<forward_list><list><vector>`
`__cpp_lib_indirect`	202502L	`<memory>`
`__cpp_lib_inplace_vector`	202406L	`<inplace_vector>`
`__cpp_lib_int_pow2`	202002L	`<bit>`	Yes
`__cpp_lib_integer_comparison_functions`	202002L	`<utility>`
`__cpp_lib_integer_sequence`	201304L	`<utility>`	Yes
`__cpp_lib_integral_constant_callable`	201304L	`<type_traits>`	Yes
`__cpp_lib_interpolate`	201902L	`<cmath><numeric>`
`__cpp_lib_invoke`	201411L	`<functional>`	Yes
`__cpp_lib_invoke_r`	202106L	`<functional>`	Yes
`__cpp_lib_ios_noreplace`	202207L	`<ios>`
`__cpp_lib_is_aggregate`	201703L	`<type_traits>`	Yes
`__cpp_lib_is_constant_evaluated`	201811L	`<type_traits>`	Yes
`__cpp_lib_is_final`	201402L	`<type_traits>`	Yes
`__cpp_lib_is_implicit_lifetime`	202302L	`<type_traits>`	Yes
`__cpp_lib_is_invocable`	201703L	`<type_traits>`	Yes
`__cpp_lib_is_layout_compatible`	201907L	`<type_traits>`	Yes
`__cpp_lib_is_nothrow_convertible`	201806L	`<type_traits>`	Yes
`__cpp_lib_is_null_pointer`	201309L	`<type_traits>`	Yes
`__cpp_lib_is_pointer_interconvertible`	201907L	`<type_traits>`	Yes
`__cpp_lib_is_scoped_enum`	202011L	`<type_traits>`	Yes
`__cpp_lib_is_sufficiently_aligned`	202411L	`<memory>`
`__cpp_lib_is_swappable`	201603L	`<type_traits>`	Yes
`__cpp_lib_is_virtual_base_of`	202406L	`<type_traits>`	Yes
`__cpp_lib_is_within_lifetime`	202306L	`<type_traits>`	Yes
`__cpp_lib_jthread`	201911L	`<stop_token><thread>`
`__cpp_lib_latch`	201907L	`<latch>`
`__cpp_lib_launder`	201606L	`<new>`	Yes
`__cpp_lib_linalg`	202412L	`<linalg>`
`__cpp_lib_list_remove_return_type`	201806L	`<forward_list><list>`
`__cpp_lib_logical_traits`	201510L	`<type_traits>`	Yes
`__cpp_lib_make_from_tuple`	201606L	`<tuple>`	Yes
`__cpp_lib_make_reverse_iterator`	201402L	`<iterator>`	Yes
`__cpp_lib_make_unique`	201304L	`<memory>`
`__cpp_lib_map_try_emplace`	201411L	`<map>`
`__cpp_lib_math_constants`	201907L	`<numbers>`
`__cpp_lib_math_special_functions`	201603L	`<cmath>`
`__cpp_lib_mdspan`	202406L	`<mdspan>`	Yes
`__cpp_lib_memory_resource`	201603L	`<memory_resource>`
`__cpp_lib_modules`	202207L		Yes
`__cpp_lib_move_iterator_concept`	202207L	`<iterator>`	Yes
`__cpp_lib_move_only_function`	202110L	`<functional>`
`__cpp_lib_node_extract`	201606L	`<map><set><unordered_map><unordered_set>`
`__cpp_lib_nonmember_container_access`	201411L	`<array><deque><forward_list><iterator><list><map><regex><set><string><unordered_map><unordered_set><vector>`	Yes
`__cpp_lib_not_fn`	202306L	`<functional>`	Yes
`__cpp_lib_null_iterators`	201304L	`<iterator>`	Yes
`__cpp_lib_optional`	202110L	`<optional>`
`__cpp_lib_optional_range_support`	202406L	`<optional>`	Yes
`__cpp_lib_out_ptr`	202311L	`<memory>`	Yes
`__cpp_lib_parallel_algorithm`	201603L	`<algorithm><numeric>`
`__cpp_lib_philox_engine`	202406L	`<random>`
`__cpp_lib_polymorphic`	202502L	`<memory>`
`__cpp_lib_polymorphic_allocator`	201902L	`<memory_resource>`
`__cpp_lib_print`	202406L	`<print><ostream>`
`__cpp_lib_quoted_string_io`	201304L	`<iomanip>`
`__cpp_lib_ranges`	202406L	`<algorithm><functional><iterator><memory><ranges>`
`__cpp_lib_ranges_as_const`	202311L	`<ranges>`	Yes
`__cpp_lib_ranges_as_rvalue`	202207L	`<ranges>`	Yes
`__cpp_lib_ranges_cache_latest`	202411L	`<ranges>`	Yes
`__cpp_lib_ranges_cartesian_product`	202207L	`<ranges>`	Yes
`__cpp_lib_ranges_chunk`	202202L	`<ranges>`	Yes
`__cpp_lib_ranges_chunk_by`	202202L	`<ranges>`	Yes
`__cpp_lib_ranges_concat`	202403L	`<ranges>`	Yes
`__cpp_lib_ranges_contains`	202207L	`<algorithm>`
`__cpp_lib_ranges_enumerate`	202302L	`<ranges>`
`__cpp_lib_ranges_find_last`	202207L	`<algorithm>`
`__cpp_lib_ranges_fold`	202207L	`<algorithm>`
`__cpp_lib_ranges_generate_random`	202403L	`<random>`
`__cpp_lib_ranges_iota`	202202L	`<numeric>`
`__cpp_lib_ranges_join_with`	202202L	`<ranges>`	Yes
`__cpp_lib_ranges_repeat`	202207L	`<ranges>`	Yes
`__cpp_lib_ranges_reserve_hint`	202502L	`<ranges>`
`__cpp_lib_ranges_slide`	202202L	`<ranges>`	Yes
`__cpp_lib_ranges_starts_ends_with`	202106L	`<algorithm>`
`__cpp_lib_ranges_stride`	202207L	`<ranges>`	Yes
`__cpp_lib_ranges_to_container`	202202L	`<ranges>`	Yes
`__cpp_lib_ranges_to_input`	202502L	`<ranges>`	Yes
`__cpp_lib_ranges_zip`	202110L	`<ranges><tuple><utility>`	Yes
`__cpp_lib_ratio`	202306L	`<ratio>`	Yes
`__cpp_lib_raw_memory_algorithms`	202411L	`<memory>`
`__cpp_lib_rcu`	202306L	`<rcu>`
`__cpp_lib_reference_from_temporary`	202202L	`<type_traits>`	Yes
`__cpp_lib_reference_wrapper`	202403L	`<functional>`	Yes
`__cpp_lib_remove_cvref`	201711L	`<type_traits>`	Yes
`__cpp_lib_result_of_sfinae`	201210L	`<functional><type_traits>`	Yes
`__cpp_lib_robust_nonmodifying_seq_ops`	201304L	`<algorithm>`
`__cpp_lib_sample`	201603L	`<algorithm>`
`__cpp_lib_saturation_arithmetic`	202311L	`<numeric>`
`__cpp_lib_scoped_lock`	201703L	`<mutex>`
`__cpp_lib_semaphore`	201907L	`<semaphore>`
`__cpp_lib_senders`	202406L	`<execution>`
`__cpp_lib_shared_mutex`	201505L	`<shared_mutex>`
`__cpp_lib_shared_ptr_arrays`	201707L	`<memory>`
`__cpp_lib_shared_ptr_weak_type`	201606L	`<memory>`
`__cpp_lib_shared_timed_mutex`	201402L	`<shared_mutex>`
`__cpp_lib_shift`	202202L	`<algorithm>`
`__cpp_lib_simd`	202502L	`<simd>`
`__cpp_lib_simd_complex`	202502L	`<simd>`
`__cpp_lib_smart_ptr_for_overwrite`	202002L	`<memory>`
`__cpp_lib_smart_ptr_owner_equality`	202306L	`<memory>`
`__cpp_lib_source_location`	201907L	`<source_location>`	Yes
`__cpp_lib_span`	202311L	`<span>`	Yes
`__cpp_lib_span_initializer_list`	202311L	`<span>`	Yes
`__cpp_lib_spanstream`	202106L	`<spanstream>`
`__cpp_lib_ssize`	201902L	`<iterator>`	Yes
`__cpp_lib_sstream_from_string_view`	202306L	`<sstream>`
`__cpp_lib_stacktrace`	202011L	`<stacktrace>`
`__cpp_lib_start_lifetime_as`	202207L	`<memory>`	Yes
`__cpp_lib_starts_ends_with`	201711L	`<string><string_view>`
`__cpp_lib_stdatomic_h`	202011L	`<stdatomic.h>`
`__cpp_lib_string_contains`	202011L	`<string><string_view>`
`__cpp_lib_string_resize_and_overwrite`	202110L	`<string>`
`__cpp_lib_string_udls`	201304L	`<string>`
`__cpp_lib_string_view`	202403L	`<string><string_view>`
`__cpp_lib_submdspan`	202411L	`<mdspan>`	Yes
`__cpp_lib_syncbuf`	201803L	`<syncstream>`
`__cpp_lib_text_encoding`	202306L	`<text_encoding>`
`__cpp_lib_three_way_comparison`	201907L	`<compare>`	Yes
`__cpp_lib_to_address`	201711L	`<memory>`	Yes
`__cpp_lib_to_array`	201907L	`<array>`	Yes
`__cpp_lib_to_chars`	202306L	`<charconv>`
`__cpp_lib_to_string`	202306L	`<string>`
`__cpp_lib_to_underlying`	202102L	`<utility>`	Yes
`__cpp_lib_transformation_trait_aliases`	201304L	`<type_traits>`	Yes
`__cpp_lib_transparent_operators`	201510L	`<memory><functional>`	Yes
`__cpp_lib_trivially_relocatable`	202502L	`<memory><type_traits>`	Yes
`__cpp_lib_tuple_element_t`	201402L	`<tuple>`	Yes
`__cpp_lib_tuple_like`	202311L	`<utility><tuple><map><unordered_map>`
`__cpp_lib_tuples_by_type`	201304L	`<utility><tuple>`	Yes
`__cpp_lib_type_identity`	201806L	`<type_traits>`	Yes
`__cpp_lib_type_trait_variable_templates`	201510L	`<type_traits>`	Yes
`__cpp_lib_uncaught_exceptions`	201411L	`<exception>`	Yes
`__cpp_lib_unordered_map_try_emplace`	201411L	`<unordered_map>`
`__cpp_lib_unreachable`	202202L	`<utility>`	Yes
`__cpp_lib_unwrap_ref`	201811L	`<type_traits>`	Yes
`__cpp_lib_variant`	202306L	`<variant>`
`__cpp_lib_void_t`	201411L	`<type_traits>`	Yes
Total number of macros: 268

A hardened implementation also defines the following macros:

Macro name	Value	Header
`__cpp_lib_hardened_array`	202502L	`<array>`
`__cpp_lib_hardened_basic_string`	202502L	`<string>`
`__cpp_lib_hardened_basic_string_view`	202502L	`<string_view>`
`__cpp_lib_hardened_bitset`	202502L	`<bitset>`
`__cpp_lib_hardened_deque`	202502L	`<deque>`
`__cpp_lib_hardened_expected`	202502L	`<expected>`
`__cpp_lib_hardened_forward_list`	202502L	`<forward_list>`
`__cpp_lib_hardened_inplace_vector`	202502L	`<inplace_vector>`
`__cpp_lib_hardened_list`	202502L	`<list>`
`__cpp_lib_hardened_mdspan`	202502L	`<mdspan>`
`__cpp_lib_hardened_optional`	202502L	`<optional>`
`__cpp_lib_hardened_span`	202502L	`<span>`
`__cpp_lib_hardened_valarray`	202502L	`<valarray>`
`__cpp_lib_hardened_vector`	202502L	`<vector>`
Total number of macros: 14

[edit]Notes

Each value in "Value" column follows the pattern:"yyyymmL", where"yyyy" is a year, and"mm" is a month when the corresponding feature-set was accepted for standardization. Some values where increased since the time of their introduction, if capabilities of given feature where extended. The table above contains only the most recent values (that is, taken from the latest C++ language draft standard). A full set of values, including the initial and intermediate ones, can be found inthis table.

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 4126	C++20 C++23	some feature-test macros for fully freestanding features were not freestanding	they are also freestanding

[edit]See also

Feature testing(C++20)	A set of preprocessor macros to test the corresponding to C++ language and library features
C++ documentation forHeaders required for a freestanding implementation
C++ documentation forPredefined Macro Symbols

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