cppdraft_translate/cppdraft/cpp/predefined.md

[cpp.predefined]

15 Preprocessing directives [cpp]

15.12 Predefined macro names [cpp.predefined]

1

#

The following macro names shall be defined by the implementation:

• (1.1)

  __cplusplus
  The integer literal 202302L. [Note 1: Future revisions of this document will replace the value of this macro with a greater value. — end note]

• (1.2)

  The names listed in Table 22.

  The macros defined in Table 22 shall be defined to the corresponding integer literal. [Note 2: Future revisions of this document might replace the values of these macros with greater values. — end note]

• (1.3)

  DATE
  The date of translation of the source file: a character string literal of the form"Mmm dd yyyy", where the names of the months are the same as those generated by theasctime function, and the first character ofdd is a space character if the value is less than 10. If the date of translation is not available, an implementation-defined valid date shall be supplied.

• (1.4)

  FILE
  The presumed name of the current source file (a character string literal).129

• (1.5)

  LINE
  The presumed line number (within the current source file) of the current source line (an integer literal).130

• (1.6)

  STDC_EMBED_NOT_FOUND, STDC_EMBED_FOUND, and STDC_EMBED_EMPTY
  The integer literals 0, 1, and 2, respectively. [Note 3: These represent values replaced from has-embed-expressions ([cpp.cond]). — end note]

• (1.7)

  STDC_HOSTED
  The integer literal 1 if the implementation is a hosted implementation or the integer literal 0 if it is a freestanding implementation ([intro.compliance]).

• (1.8)

  STDCPP_DEFAULT_NEW_ALIGNMENT
  An integer literal of type std​::​size_t whose value is the alignment guaranteed by a call to operator new(std​::​size_t) or operator new. [Note 4: Larger alignments will be passed tooperator new(std​::​size_t, std​::​align_val_t), etc. ([expr.new]). — end note]

• (1.9)

  STDCPP_FLOAT16_T
  Defined as the integer literal 1 if and only if the implementation supports the ISO/IEC 60559 floating-point interchange format binary16 as an extended floating-point type ([basic.extended.fp]).

• (1.10)

  STDCPP_FLOAT32_T
  Defined as the integer literal 1 if and only if the implementation supports the ISO/IEC 60559 floating-point interchange format binary32 as an extended floating-point type.

• (1.11)

  STDCPP_FLOAT64_T
  Defined as the integer literal 1 if and only if the implementation supports the ISO/IEC 60559 floating-point interchange format binary64 as an extended floating-point type.

• (1.12)

  STDCPP_FLOAT128_T
  Defined as the integer literal 1 if and only if the implementation supports the ISO/IEC 60559 floating-point interchange format binary128 as an extended floating-point type.

• (1.13)

  STDCPP_BFLOAT16_T
  Defined as the integer literal 1 if and only if the implementation supports an extended floating-point type with the properties of the typedef-name std​::​bfloat16_t as described in [basic.extended.fp].

• (1.14)

  TIME
  The time of translation of the source file: a character string literal of the form"hh:mm:ss" as in the time generated by theasctime function. If the time of translation is not available, an implementation-defined valid time shall be supplied.

Table 22 — Feature-test macros [tab:cpp.predefined.ft]

🔗 Macro name	Value
🔗 __cpp_aggregate_bases	201603L
🔗 __cpp_aggregate_nsdmi	201304L
🔗 __cpp_aggregate_paren_init	201902L
🔗 __cpp_alias_templates	200704L
🔗 __cpp_aligned_new	201606L
🔗 __cpp_attributes	200809L
🔗 __cpp_auto_cast	202110L
🔗 __cpp_binary_literals	201304L
🔗 __cpp_capture_star_this	201603L
🔗 __cpp_char8_t	202207L
🔗 __cpp_concepts	202002L
🔗 __cpp_conditional_explicit	201806L
🔗 __cpp_constexpr	202406L
🔗 __cpp_constexpr_dynamic_alloc	201907L
🔗 __cpp_constexpr_exceptions	202411L
🔗 __cpp_constexpr_in_decltype	201711L
🔗 __cpp_constexpr_virtual_inheritance	202506L
🔗 __cpp_consteval	202211L
🔗 __cpp_constinit	201907L
🔗 __cpp_contracts	202502L
🔗 __cpp_decltype	200707L
🔗 __cpp_decltype_auto	201304L
🔗 __cpp_deduction_guides	201907L
🔗 __cpp_delegating_constructors	200604L
🔗 __cpp_deleted_function	202403L
🔗 __cpp_designated_initializers	201707L
🔗 __cpp_enumerator_attributes	201411L
🔗 __cpp_expansion_statements	202506L
🔗 __cpp_explicit_this_parameter	202110L
🔗 __cpp_fold_expressions	201603L
🔗 __cpp_generic_lambdas	201707L
🔗 __cpp_guaranteed_copy_elision	201606L
🔗 __cpp_hex_float	201603L
🔗 __cpp_if_consteval	202106L
🔗 __cpp_if_constexpr	201606L
🔗 __cpp_impl_coroutine	201902L
🔗 __cpp_impl_destroying_delete	201806L
🔗 __cpp_impl_three_way_comparison	201907L
🔗 __cpp_impl_reflection	202506L
🔗 __cpp_implicit_move	202207L
🔗 __cpp_inheriting_constructors	201511L
🔗 __cpp_init_captures	201803L
🔗 __cpp_initializer_lists	200806L
🔗 __cpp_inline_variables	201606L
🔗 __cpp_lambdas	200907L
🔗 __cpp_modules	201907L
🔗 __cpp_multidimensional_subscript	202211L
🔗 __cpp_named_character_escapes	202207L
🔗 __cpp_namespace_attributes	201411L
🔗 __cpp_noexcept_function_type	201510L
🔗 __cpp_nontype_template_args	201911L
🔗 __cpp_nontype_template_parameter_auto	201606L
🔗 __cpp_nsdmi	200809L
🔗 __cpp_pack_indexing	202311L
🔗 __cpp_placeholder_variables	202306L
🔗 __cpp_pp_embed	202502L
🔗 __cpp_range_based_for	202211L
🔗 __cpp_raw_strings	200710L
🔗 __cpp_ref_qualifiers	200710L
🔗 __cpp_return_type_deduction	201304L
🔗 __cpp_rvalue_references	200610L
🔗 __cpp_size_t_suffix	202011L
🔗 __cpp_sized_deallocation	201309L
🔗 __cpp_static_assert	202306L
🔗 __cpp_static_call_operator	202207L
🔗 __cpp_structured_bindings	202411L
🔗 __cpp_template_parameters	202502L
🔗 __cpp_template_template_args	201611L
🔗 __cpp_threadsafe_static_init	200806L
🔗 __cpp_trivial_relocatability	202502L
🔗 __cpp_trivial_union	202502L
🔗 __cpp_unicode_characters	200704L
🔗 __cpp_unicode_literals	200710L
🔗 __cpp_user_defined_literals	200809L
🔗 __cpp_using_enum	201907L
🔗 __cpp_variable_templates	201304L
🔗 __cpp_variadic_friend	202403L
🔗 __cpp_variadic_templates	200704L
🔗 __cpp_variadic_using	201611L

2

#

The following macro names are conditionally defined by the implementation:

• (2.1)

  STDC
  Whether STDC is predefined and if so, what its value is, are implementation-defined.

• (2.2)

  STDC_MB_MIGHT_NEQ_WC
  The integer literal 1, intended to indicate that, in the encoding forwchar_t, a member of the basic character set need not have a code value equal to its value when used as the lone character in an ordinary character literal.

• (2.3)

  STDC_VERSION
  Whether STDC_VERSION is predefined and if so, what its value is, are implementation-defined.

• (2.4)

  STDC_ISO_10646
  An integer literal of the form yyyymmL (for example, 199712L). Whether STDC_ISO_10646 is predefined and if so, what its value is, are implementation-defined.

• (2.5)

  STDCPP_THREADS
  Defined, and has the value integer literal 1, if and only if a program can have more than one thread of execution.

3

#

The values of the predefined macros (except for__FILE__ and__LINE__) remain constant throughout the translation unit.

4

#

If any of the pre-defined macro names in this subclause, or the identifierdefined, is the subject of a#define or a#undef preprocessing directive, the program is ill-formed.

Any other predefined macro names shall begin with a leading underscore followed by an uppercase letter or a second underscore.

129)129)

The presumed source file name can be changed by the #line directive.

130)130)

The presumed line number can be changed by the #line directive.