C++ keywords

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C++ language
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decltype (C++11)
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alignas (C++11)
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This is a list of reserved keywords in C++. Since they are used by the language, these keywords are not available for re-definition or overloading.

alignas (since C++11)
alignof (since C++11)
and
and_eq
asm
atomic_cancel (TM TS)
atomic_commit (TM TS)
atomic_noexcept (TM TS)
auto(1)
bitand
bitor
bool
break
case
catch
char
char8_t (since C++20)
char16_t (since C++11)
char32_t (since C++11)
class(1)
compl
concept (since C++20)
const
consteval (since C++20)
constexpr (since C++11)
const_cast
continue
co_await (since C++20)
co_return (since C++20)
co_yield (since C++20)
decltype (since C++11)
default(1)

delete(1)
do
double
dynamic_cast
else
enum
explicit
export(1)(3)
extern(1)
false
float
for
friend
goto
if
inline(1)
int
long
mutable(1)
namespace
new
noexcept (since C++11)
not
not_eq
nullptr (since C++11)
operator
or
or_eq
private
protected
public
reflexpr (reflection TS)

register(2)
reinterpret_cast
requires (since C++20)
return
short
signed
sizeof(1)
static
static_assert (since C++11)
static_cast
struct(1)
switch
synchronized (TM TS)
template
this
thread_local (since C++11)
throw
true
try
typedef
typeid
typename
union
unsigned
using(1)
virtual
void
volatile
wchar_t
while
xor
xor_eq

  • (1) - meaning changed or new meaning added in C++11.
  • (2) - meaning changed in C++17.
  • (3) - meaning changed in C++20.

Note that and, bitor, or, xor, compl, bitand, and_eq, or_eq, xor_eq, not, and not_eq (along with the digraphs <%, %>, <:, :>, %:, and %:%:) provide an alternative way to represent standard tokens.

In addition to keywords, there are identifiers with special meaning, which may be used as names of objects or functions, but have special meaning in certain contexts.

override (C++11)
final (C++11)
audit (C++20)
axiom (C++20)
import (C++20)
module (C++20)
transaction_safe (TM TS)
transaction_safe_dynamic (TM TS)

Also, all identifiers that contain a double underscore __ in any position and each identifier that begins with an underscore followed by an uppercase letter is always reserved and all identifiers that begin with an underscore are reserved for use as names in the global namespace. See identifiers for more details.

The namespace std is used to place names of the standard C++ library. See Extending namespace std for the rules about adding names to it.

The name posix is reserved for a future top-level namespace. The behavior is undefined if a program declares or defines anything in that namespace.

(since C++11)

The following tokens are recognized by the preprocessor when in context of a preprocessor directive:

if
elif
else
endif

ifdef
ifndef
define
undef

include
line
error
pragma

defined
__has_include (since C++17)
__has_cpp_attribute (since C++20)

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

_Pragma(since C++11)

See also