Macros related to language levels

The following macros can be tested for C99 features, features related to GNU C or C++, and other IBM language extensions. All of these macros except C++ only __cplusplus, __STDC__ C++ only ends , and C only __STDC_VERSION__ C only ends are predefined to a value of 1 by a specific language level, represented by a suboption of the LANGLVL compiler option, or any invocation or pragma that implies that suboption. If the suboption enabling the feature is not in effect, then the macro is undefined.

Table 1. Predefined macros for language features
Predefined macro name	Description	Predefined when the following language level is in effect
__ANSI__	Indicates that only language constructs that support the ISO C89 Standard are allowed.	ansi \| stdc89 \| stdc99
__BOOL__	Indicates that the `bool` keyword is accepted.	Always defined except when NOKEYWORD(bool) is in effect.
__C99_BOOL	Indicates support for the `_Bool` data type.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_COMPLEX	Indicates that the support for C99 complex types is enabled or that the C99 complex header should be included.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_CPLUSCMT	Indicates support for C++ style comments	extc1x \| stdc99 \| extc99 \| stdc89 \| extc89 \| extended (also SSCOM)
__C99_COMPOUND_LITERAL	Indicates support for compound literals.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_DESIGNATED_INITIALIZER	Indicates support for designated initialization.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_DUP_TYPE_QUALIFIER	Indicates support for duplicated type qualifiers.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_EMPTY_MACRO_ARGUMENTS	Indicates support for empty macro arguments.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_FLEXIBLE_ARRAY_MEMBER	Indicates support for flexible array members.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99__FUNC__	Indicates support for the `__func__` predefined identifier.	extc1x \| stdc99 \| extc99 \| extc89 \| extended extended \| extended0x \|c99__func__
__C99_HEX_FLOAT_CONST	Indicates support for hexadecimal floating constants.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_INLINE	Indicates support for the `inline` function specifier.	extc1x \| stdc99 \| extc99
__C99_LLONG	Indicates support for C99-style `long long` data types and literals.	extc1x \| stdc99 \| extc99 extended0x \| c99longlong
__C99_MACRO_WITH_VA_ARGS	Indicates support for function-like macros with variable arguments.	extc1x \| stdc99 \| extc99 \| extc89 \| extended extended
__C99_MAX_LINE_NUMBER	Indicates that the maximum line number is 2147483647.	extc1x \| stdc99 \| extc99 \| extc89 \| extended extended0x \| c99preprocessor
__C99_MIXED_DECL_AND_CODE	Indicates support for mixed declaration and code.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_MIXED_STRING_CONCAT	Indicates support for concatenation of wide string and non-wide string literals.	extc1x \| stdc99 \| extc99 \| extc89 \| extended extended0x \| c99preprocessor
__C99_NON_LVALUE_ARRAY_SUB	Indicates support for non-lvalue subscripts for arrays.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_NON_CONST_AGGR_INITIALIZER	Indicates support for non-constant aggregate initializers.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_PRAGMA_OPERATOR	Indicates support for the `_Pragma` operator.	extc1x \| stdc99 \| extc99 \| extc89 \| extended extended
__C99_REQUIRE_FUNC_DECL	Indicates that implicit function declaration is not supported.	stdc99
__C99_RESTRICT	Indicates support for the C99 `restrict` qualifier.	extc1x \| stdc99 \| extc99
__C99_STATIC_ARRAY_SIZE	Indicates support for the `static` keyword in array parameters to functions.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_STD_PRAGMAS	Indicates support for standard pragmas.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_TGMATH	Indicates support for type-generic macros in tgmath.h	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_UCN	Indicates support for universal character names.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_VAR_LEN_ARRAY	Indicates support for variable length arrays.	extc1x \| stdc99 \| extc99 \| extc89 \| extended
__C99_VARIABLE_LENGTH_ARRAY	Indicates support for variable length arrays.	extended \| extended0x \| c99vla
__COMMONC__	Indicates that language constructs defined by XPG are allowed.	commonc
__COMPATMATH__	Indicates that the newer C++ function declarations are not to be introduced by the math.h header file.	oldmath
_EXT	Used in features.h to control the availability of extensions to the general ISO run-time libraries.	LIBEXT, or any LANGLVL suboption that implies it. (See the description of the LANGLVL option in the z/OS XL C/C++ User's Guide for a list of suboptions that imply LIBEXT.)
__EXTENDED__	Indicates that language extensions are supported.	extended
__IBM_COMPUTED_GOTO	Indicates support for computed `goto` statements.	extc1x \| extc99 \| extc89 \| extended extended \| extended0x \| gnu_computedgoto
__IBM_INCLUDE_NEXT	Indicates support for the `#include_next` preprocessing directive.	Always defined.
__IBM_LABEL_VALUE	Indicates support for labels as values.	extc1x \| extc99 \| extc89 \| extended extended \| extended0x \|gnu_labelvalue
__IBM__TYPEOF__	Indicates support for the `__typeof__` keyword.	Always defined extended \| extended0x
__IBMC_COMPLEX_INIT	Indicates support for the macro based initialization of complex types: float _Complex, double _Complex, and long double _Complex.	extc1x
__IBMC_GENERIC	Indicates support for the generic selection feature.	extc89 \| extc99 \| extended \| extc1x
__IBMC_NORETURN	Indicates support for the `_Noreturn` function specifier.	extc89 \| extc99 \| extended \| extc1x extended \| extended0x \| c1xnoreturn
__IBMC_STATIC_ASSERT	Indicates support for the static assertions feature.	extc89 \| extc99 \| extended \| extc1x
__IBMCPP_AUTO_TYPEDEDUCTION	Indicates support for the auto type deduction feature.	extended0x \| autotypededuction
__IBMCPP_C99_LONG_LONG	Indicates support for the C99 `long long` feature.	extended0x \| c99longlong
__IBMCPP_C99_PREPROCESSOR	Indicates support for the C99 preprocessor features adopted in the C++11 standard.	extended0x \| c99preprocessor
__IBMCPP_COMPLEX_INIT	Indicates support for the initialization of complex types: float _Complex, double _Complex, and long double _Complex.	extended
__IBMCPP_CONSTEXPR	Indicates support for the generalized constant expressions feature.	extended0x \| constexpr
__IBMCPP_DECLTYPE	Indicates support for the decltype feature.	extended0x \| decltype
__IBMCPP_DEFAULTED_AND_DELETED_FUNCTIONS	Indicates support for the defaulted and deleted functions feature.	extended0x \| defaultanddelete
__IBMCPP_DELEGATING_CTORS	Indicates support for the delegating constructors feature.	extended0x \| delegatingctors
__IBMCPP_EXPLICIT_CONVERSION_OPERATORS	Indicates support for the explicit conversion operators feature.	extended0x \| explicitconversionoperators
__IBMCPP_EXTENDED_FRIEND	Indicates support for the extended friend declarations feature.	extended0x \| extendedfriend
__IBMCPP_EXTERN_TEMPLATE	Indicates support for the explicit instantiation declarations feature.	extended \| extended0x \| externtemplate
__IBMCPP_INLINE_NAMESPACE	Indicates support for the inline namespace definitions feature.	extended0x \| inlinenamespace
__IBMCPP_REFERENCE_COLLAPSING	Indicates support for the reference collapsing feature.	extended0x \| referencecollapsing
__IBMCPP_RIGHT_ANGLE_BRACKET	Indicates support for the right angle bracket feature.	extended0x \| rightanglebracket
__IBMCPP_RVALUE_REFERENCES	Indicates support for the rvalue references feature.	extended0x \| rvaluereferences
__IBMCPP_SCOPED_ENUM	Indicates support for the scoped enumeration feature.	extended0x \| scopedenum
__IBMCPP_STATIC_ASSERT	Indicates support for the static assertions feature.	extended0x \| static_assert
__IBMCPP_VARIADIC_TEMPLATES	Indicates support for the variadic templates feature.	extended0x \| variadic[templates]
_LONG_LONG	Indicates support for `long long` data types.	extc1x \| stdc99 \| extc99 \| \| stdc89 \| extc89 \| extended \| longlong extended0x \| c99longlong \| extended \| longlong
_MI_BUILTIN	Indicates that the machine instruction built-in functions are available.	LIBEXT, or any LANGLVL suboption that implies it. (See the description of the LANGLVL option in the z/OS XL C/C++ User's Guide for a list of suboptions that imply LIBEXT.)
__RESTRICT__	Indicates that the `__restrict__` or `__restrict` keywords are supported.	Predefined at all language levels.
__SAA__	Indicates that only language constructs that support the most recent level of SAA C standards are allowed.	saa
__SAA_L2__	Indicates that only language constructs that conform to SAA Level 2 C standards are allowed.	saal2