keywords-cpp.md

title	ms.custom	ms.date	helpviewer_keywords	ms.assetid
Keywords (C++)	index-page	10/10/2018	keywords [C++]	d7ca94a8-f785-41ce-9f73-d3c4fd508489

Keywords (C++)

Keywords are predefined reserved identifiers that have special meanings. They cannot be used as identifiers in your program. The following keywords are reserved for Microsoft C++. Names with leading underscores, and names followed by (C++/CLI) are Microsoft extensions.

__abstract 2	__alignof Operator 4	__asm 4	__assume 4
__based 4	__box 2	__cdecl 4	__declspec 4
__delegate 2	__event	__except 4	__fastcall 4
__finally 4	__forceinline 4	__gc 2	__hook 3
__identifier	__if_exists	__if_not_exists	__inline 4
__int16 4	__int32 4	__int64 4	__int8 4
__interface	__leave 4	__m128	__m128d
__m128i	__m64	__multiple_inheritance 4	__nogc 2
__noop	__pin 2	__property 2	__ptr32 4
__ptr644	__raise	__restrict 4	__sealed 2
__single_inheritance4	__sptr4	__stdcall 4	__super
__thiscall	__try_cast 2	__unaligned 4	__unhook 3
__uptr 4	__uuidof 4	__value 2	__vectorcall 4
__virtual_inheritance 4	__w64 4	__wchar_t	abstract(C++/CLI)
alignas	array(C++/CLI)	auto	bool
break	case	catch	char
char16_t	char32_t	class	const
const_cast	constexpr	continue	decltype
default	delegate(C++/CLI)	delete	deprecated 1
dllexport 1	dllimport 1	do	double
dynamic_cast	else	enum	enum class
enum struct	event(C++/CLI)	explicit	extern
false	finally	float	for
for each in	friend	friend_as	gcnew(C++/CLI)
generic(C++/CLI)	goto	if	initonly
inline	int	interface class(C++/CLI)	interface struct(C++/CLI)
interior_ptr(C++/CLI)	literal(C++/CLI)	long	mutable
naked 1	namespace	new(C++/CLI)	new
noexcept	noinline 1	noreturn 1	nothrow 1
novtable 1	nullptr	operator	private
property(C++/CLI)	property 1	protected	public
ref class	ref struct	register	reinterpret_cast
return	safecast	sealed(C++/CLI)	selectany 1
short	signed	sizeof	static
static_assert	static_cast	struct	switch
template	this	thread 1	throw
true	try	typedef	typeid
typeid	typename	union	unsigned
using declaration	using directive	uuid 1	value class(C++/CLI)
value struct(C++/CLI)	virtual	void	volatile
while

¹ Extended attributes for the __declspec keyword.

² Applicable to Managed Extensions for C++ only. This syntax is now deprecated. See Component Extensions for Runtime Platforms for more information.

³ Intrinsic function used in event handling.

⁴ For backward compatibility with previous versions, these keywords are available both with two leading underscores and a single leading underscore when Microsoft extensions are enabled (the default).

Microsoft Specific

In Microsoft C++, identifiers with two leading underscores are reserved for compiler implementations. Therefore, the Microsoft convention is to precede Microsoft-specific keywords with double underscores. These words cannot be used as identifier names.

Microsoft extensions are enabled by default. To ensure that your programs are fully portable, you can disable Microsoft extensions by specifying the /Za (Disable language extensions) option during compilation. When you do this, some Microsoft-specific keywords are disabled.

When Microsoft extensions are enabled, you can use the Microsoft-specific keywords in your programs. For ANSI compliance, these keywords are prefaced by a double underscore. For backward compatibility, single-underscore versions of many of the double-underscored keywords are supported. In addition, __cdecl is available with no leading underscore.

The __asm keyword replaces C++ asm syntax. asm is reserved for compatibility with other C++ implementations, but not implemented. Use __asm.

The __based keyword has limited uses for 32-bit and 64-bit target compilations.

END Microsoft Specific

See also

Lexical Conventions
C++ Built-in Operators, Precedence and Associativity