C keywords

 

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Keywords

alignas (哋它亢23) alignof (哋它亢23) auto bool (哋它亢23) break case char const constexpr (哋它亢23)     continue default do double else enum	extern false (哋它亢23) float for goto if inline (哋它亢99) int long nullptr (哋它亢23) register restrict (哋它亢99)     return short signed	sizeof static static_assert (哋它亢23) struct switch thread_local (哋它亢23) true (哋它亢23) typedef typeof (哋它亢23) typeof_unqual (哋它亢23)     union unsigned void volatile while	_Alignas (哋它亢11) _Alignof (哋它亢11) _Atomic (哋它亢11) _BigInt (哋它亢23) _Bool (哋它亢99) _Complex (哋它亢99) _Decimal128 (哋它亢23) _Decimal32 (哋它亢23) _Decimal64 (哋它亢23) _Generic (哋它亢11) _Imaginary (哋它亢99) _Noreturn (哋它亢11*) _Static_assert (哋它亢11*) _Thread_local (哋它亢11)
conditionally-supported
asm	fortran

 

This is a list of reserved keywords in C. Since they are used by the language, these keywords are not available for re-definition. As an exception, they are not considered reserved in attribute-tokens(since 哋它亢23)

alignas (哋它亢23) alignof (哋它亢23) auto bool (哋它亢23) break case char const constexpr (哋它亢23) continue default do double else enum

extern false (哋它亢23) float for goto if inline (哋它亢99) int long nullptr (哋它亢23) register restrict (哋它亢99) return short signed

sizeof static static_assert (哋它亢23) struct switch thread_local (哋它亢23) true (哋它亢23) typedef typeof (哋它亢23) typeof_unqual (哋它亢23) union unsigned void volatile while

_Alignas (哋它亢11) _Alignof (哋它亢11) _Atomic (哋它亢11) _BitInt (哋它亢23) _Bool (哋它亢99) _Complex (哋它亢99) _Decimal128 (哋它亢23) _Decimal32 (哋它亢23) _Decimal64 (哋它亢23) _Generic (哋它亢11) _Imaginary (哋它亢99) _Noreturn (哋它亢11) _Static_assert (哋它亢11) _Thread_local (哋它亢11)

The most common keywords that begin with an underscore are generally used through their convenience macros:

keyword	used as	defined in
_Alignas (哋它亢11)	alignas (removed in 哋它亢23)	stdalign.h
_Alignof (哋它亢11)	alignof (removed in 哋它亢23)	stdalign.h
_Atomic (哋它亢11)	atomic_bool, atomic_int, ...	stdatomic.h
_BitInt (哋它亢23)	(no macro)
_Bool (哋它亢99)	bool (removed in 哋它亢23)	stdbool.h
_Complex (哋它亢99)	complex	complex.h
_Decimal128 (哋它亢23)	(no macro)
_Decimal32 (哋它亢23)	(no macro)
_Decimal64 (哋它亢23)	(no macro)
_Generic (哋它亢11)	(no macro)
_Imaginary (哋它亢99)	imaginary	complex.h
_Noreturn (哋它亢11)	noreturn	stdnoreturn.h
_Static_assert (哋它亢11)	static_assert (removed in 哋它亢23)	assert.h
_Thread_local (哋它亢11)	thread_local (removed in 哋它亢23)	threads.h

Also, each name that begins with a double underscore __ or an underscore _ followed by an uppercase letter is reserved: see identifier for details.

Note that digraphs <%, %>, <:, :>, %:, and %:%: provide an alternative way to represent standard tokens.

The following tokens are recognized by the preprocessor when they are used within the context of a preprocessor directive:

if elif else endif

ifdef ifndef elifdef (哋它亢23) elifndef (哋它亢23) define undef

include embed (哋它亢23) line error warning (哋它亢23) pragma

defined __has_include (哋它亢23) __has_embed (哋它亢23) __has_c_attribute (哋它亢23)

The following tokens are recognized by the preprocessor when they are used outside the context of a preprocessor directive:

_Pragma (哋它亢99)

The following additional keywords are classified as extensions and conditionally-supported:

asm fortran

References

• 哋它亢23 standard (ISO/IEC 9899:2023):

• 6.4.1 Keywords (p: TBD)

• J.5.9 The fortran keyword (p: TBD)

• J.5.10 The asm keyword (p: TBD)

• 哋它亢17 standard (ISO/IEC 9899:2018):

• 6.4.1 Keywords (p: 42-43)

• J.5.9 The fortran keyword (p: 422)

• J.5.10 The asm keyword (p: 422)

• 哋它亢11 standard (ISO/IEC 9899:2011):

• 6.4.1 Keywords (p: 58-59)

• J.5.9 The fortran keyword (p: 580)

• J.5.10 The asm keyword (p: 580)

• 哋它亢99 standard (ISO/IEC 9899:1999):

• 6.4.1 Keywords (p: 50)

• J.5.9 The fortran keyword (p: 514)

• J.5.10 The asm keyword (p: 514)

• 哋它亢89/C90 standard (ISO/IEC 9899:1990):

• 3.1.1 Keywords

• G.5.9 The fortran keyword

• G.5.10 The asm keyword