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 are predefined to a value of 1 by a specific language level, represented by a suboption of the -qlanglvl 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. For descriptions of the features related to these macros, see the XL C/C++ Language Reference.

Table 1. Predefined macros for language features
Predefined macro name	Description	Predefined when the following language level is in effect
__BOOL__	Indicates that the `bool` keyword is accepted.	Always defined except when -qnokeyword=bool is in effect.
__C99_BOOL	Indicates support for the `_Bool` data type.	stdc99 \| extc99 \| extc89 \| extended
__C99_COMPLEX	Indicates support for complex data types.	stdc99 \| extc99 \| extc89 \| extended
__C99_COMPLEX_HEADER__	Indicates support for C99-style complex headers.	c99complexheader
__C99_CPLUSCMT	Indicates support for C++ style comments	stdc99 \| extc99 \| stdc 89 \| extc89 \| extended (also -qcpluscmt)
__C99_COMPOUND_LITERAL	Indicates support for compound literals.	stdc99 \| extc99 \| extc89 \| extended extended \| extended0x
__C99_DESIGNATED_INITIALIZER	Indicates support for designated initialization.	stdc99 \| extc99 \| extc89 \| extended
__C99_DUP_TYPE_QUALIFIER	Indicates support for duplicated type qualifiers.	stdc99 \| extc99 \| extc89 \| extended
__C99_EMPTY_MACRO_ARGUMENTS	Indicates support for empty macro arguments.	stdc99 \| extc99 \| extc89 \| extended
__C99_FLEXIBLE_ARRAY_MEMBER	Indicates support for flexible array members.	stdc99 \| extc99 \| extc89 \| extended
__C99__FUNC__	Indicates support for the `__func__` predefined identifier.	stdc99 \| extc99 \| extc89 \| extended extended \| extended0x \|c99__func__
__C99_HEX_FLOAT_CONST	Indicates support for hexadecimal floating constants.	stdc99 \| extc99 \| extc89 \| extended extended \| extended0x \| c99hexfloat
__C99_INLINE	Indicates support for the `inline` function specifier.	stdc99 \| extc99 (also -qkeyword=inline)
__C99_LLONG	Indicates support for C99-style `long long` data types and literals.	stdc99 \| extc99 extended0x \| c99longlong
__C99_MACRO_WITH_VA_ARGS	Indicates support for function-like macros with variable arguments.	stdc99 \| extc99 \| extc89 \| extended extended \| extended0x \| varargmacros
__C99_MAX_LINE_NUMBER	Indicates that the maximum line number is 2147483647.	stdc99 \| extc99 \| extc89 \| extended extended0x \| c99preprocessor
__C99_MIXED_DECL_AND_CODE	Indicates support for mixed declaration and code.	stdc99 \| extc99 \| extc89 \| extended
__C99_MIXED_STRING_CONCAT	Indicates support for concatenation of wide string and non-wide string literals.	stdc99 \| extc99 \| extc89 \| extended extended0x \| c99preprocessor
__C99_NON_LVALUE_ARRAY_SUB	Indicates support for non-lvalue subscripts for arrays.	stdc99 \| extc99 \| extc89 \| extended
__C99_NON_CONST_AGGR_INITIALIZER	Indicates support for non-constant aggregate initializers.	stdc99 \| extc99 \| extc89 \| extended
__C99_PRAGMA_OPERATOR	Indicates support for the `_Pragma` operator.	stdc99 \| extc99 \| extc89 \| extended extended extended0x
__C99_REQUIRE_FUNC_DECL	Indicates that implicit function declaration is not supported.	stdc99
__C99_RESTRICT	Indicates support for the C99 `restrict` qualifier.	stdc99 \| extc99 (also -qkeyword=restrict) extended \| extended0x (also -qkeyword=restrict)
__C99_STATIC_ARRAY_SIZE	Indicates support for the `static` keyword in array parameters to functions.	stdc99 \| extc99 \| extc89 \| extended
__C99_STD_PRAGMAS	Indicates support for standard pragmas.	stdc99 \| extc99 \| extc89 \| extended
__C99_TGMATH	Indicates support for type-generic macros in tgmath.h	stdc99 \| extc99 \| extc89 \| extended
__C99_UCN	Indicates support for universal character names.	stdc99 \| extc99 \| ucs ucs
__C99_VAR_LEN_ARRAY	Indicates support for variable length arrays.	stdc99 \| extc99 \| extc89 \| extended
__C99_VARIABLE_LENGTH_ARRAY	Indicates support for variable length arrays.	extended \| extended0x \| c99vla
__DIGRAPHS__	Indicates support for digraphs.	stdc99 \| extc99 \| extc89 \| extended (also -qdigraph) extended \| extended0x \| compat366 \| strict98(also -qdigraph)
__EXTENDED__	Indicates that language extensions are supported.	extended
__IBM__ALIGN	Indicates support for the `__align` specifier.	Always defined except when -qnokeyword=__alignof is specified
__IBM__ALIGNOF__	Indicates support for the `__alignof__` operator.	extc99 \| extc89 \| extended extended
__IBM_ATTRIBUTES	Indicates support for type, variable, and function attributes.	extc99 \| extc89 \| extended extended \| extended0x
__IBM_COMPUTED_GOTO	Indicates support for computed `goto` statements.	extc99 \| extc89 \| extended extended \| extended0x \| gnu_computedgoto
__IBM_EXTENSION_KEYWORD	Indicates support for the `__extension__` keyword.	extc99 \| extc89 \| extended extended \| extended0x \| compat366 \| strict98
__IBM_GCC__INLINE__	Indicates support for the GCC `__inline__` specifier.	extc99 \| extc89 \| extended
__IBM_DOLLAR_IN_ID	Indicates support for dollar signs in identifiers.	extc99 \| extc89 \| extended
__IBM_GENERALIZED_LVALUE	Indicates support for generalized lvalues.	extc99 \| extc89 \| extended
__IBM_INCLUDE_NEXT	Indicates support for the `#include_next` preprocessing directive.	Always defined Always defined except when -qlanglvl=nognu_include_next is in effect.
__IBM_LABEL_VALUE	Indicates support for labels as values.	extc99 \| extc89 \| extended extended \| extended0x \|gnu_labelvalue
__IBM_LOCAL_LABEL	Indicates support for local labels.	extc99 \| extc89 \| extended extended \| extended0x \| gnu_locallabel
__IBM_MACRO_WITH_VA_ARGS	Indicates support for variadic macro extensions.	extc99 \| extc89 \| extended extended \| extended0x \| gnu_varargmacros
_IBM_NESTED_FUNCTION	Indicates support for nested functions.	extc99 \| extc89 \| extended
__IBM_PP_PREDICATE	Indicates support for `#assert`, `#unassert`, `#cpu`, `#machine`, and `#system` preprocessing directives.	extc99 \| extc89 \| extended
__IBM_PP_WARNING	Indicates support for the `#warning` preprocessing directive.	extc99 \| extc89 \| extended
__IBM_REGISTER_VARS	Indicates support for variables in specified registers.	Always defined.
__IBM__TYPEOF__	Indicates support for the `__typeof__ or typeof` keyword.	always defined extended \| extended0x (Also -qkeyword=typeof)
__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++0x standard.	extended0x \| c99preprocessor
__IBMCPP_DECLTYPE	Indicates support for the decltype feature.	extended0x \| decltype
__IBMCPP_DELEGATING_CTORS	Indicates support for the delegating constructors feature.	extended0x \| delegatingctors
__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_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.	stdc99 \| extc99 \| \| stdc89 \| extc89 \| extended (also -qlonglong) extended0x \| c99longlong \| extended (also -qlonglong)
__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
__STDC__	Indicates that the compiler conforms to the ANSI/ISO C standard.	Predefined to 1 if ANSI/ISO C standard conformance is in effect.
__STDC_HOSTED__	Indicates that the implementation is a hosted implementation of the ANSI/ISO C standard. (That is, the hosted environment has all the facilities of the standard C available).	stdc99 \| extc99 extended0x
__STDC_VERSION__	Indicates the version of ANSI/ISO C standard which the compiler conforms to.	The format is yyyymmL. (For example, the format is 199901L for C99.)