This summary of C++ syntax is intended to be an aid to comprehension. It is not an exact statement of the language. In particular, the grammar described here accepts a superset of valid C++ constructs. Disambiguation rules ([stmt.ambig], [dcl.spec], [class.member.lookup]) must be applied to distinguish expressions from declarations. Further, access control, ambiguity, and type rules must be used to weed out syntactically valid but meaningless constructs.
New context-dependent keywords are introduced into a program by typedef ([dcl.typedef]), namespace ([namespace.def]), class (clause [class]), enumeration ([dcl.enum]), and template (clause [temp]) declarations.
typedef-name: identifier
namespace-name: original-namespace-name namespace-alias original-namespace-name: identifier namespace-alias: identifier
class-name: identifier simple-template-id
enum-name: identifier
template-name: identifier
Note that a typedef-name naming a class is also a class-name ([class.name]).
hex-quad: hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
universal-character-name: \u hex-quad \U hex-quad hex-quad
preprocessing-token: header-name identifier pp-number character-literal user-defined-character-literal string-literal user-defined-string-literal preprocessing-op-or-punc each non-white-space character that cannot be one of the above
token: identifier keyword literal operator punctuator
header-name: < h-char-sequence > " q-char-sequence "
h-char-sequence: h-char h-char-sequence h-char
h-char: any member of the source character set except new-line and >
q-char-sequence: q-char q-char-sequence q-char
q-char: any member of the source character set except new-line and "
pp-number: digit . digit pp-number digit pp-number identifier-nondigit pp-number e sign pp-number E sign pp-number .
identifier: identifier-nondigit identifier identifier-nondigit identifier digit
identifier-nondigit: nondigit universal-character-name other implementation-defined characters
nondigit: one of a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _
digit: one of 0 1 2 3 4 5 6 7 8 9
preprocessing-op-or-punc: one of { } [ ] # ## ( ) <: :> <% %> %: %:%: ; : ... new delete ? :: . .* + - * / % ^ & | ~ ! = < > += -= *= /= %= ^= &= |= << >> >>= <<= == != <= >= && || ++ -- , ->* -> and and_eq bitand bitor compl not not_eq or or_eq xor xor_eq
literal: integer-literal character-literal floating-literal string-literal boolean-literal pointer-literal user-defined-literal
integer-literal: decimal-literal integer-suffixopt octal-literal integer-suffixopt hexadecimal-literal integer-suffixopt
decimal-literal: nonzero-digit decimal-literal digit
octal-literal: 0 octal-literal octal-digit
hexadecimal-literal: 0x hexadecimal-digit 0X hexadecimal-digit hexadecimal-literal hexadecimal-digit
nonzero-digit: one of 1 2 3 4 5 6 7 8 9
octal-digit: one of 0 1 2 3 4 5 6 7
hexadecimal-digit: one of 0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F
integer-suffix: unsigned-suffix long-suffixopt unsigned-suffix long-long-suffixopt long-suffix unsigned-suffixopt long-long-suffix unsigned-suffixopt
unsigned-suffix: one of u U
long-suffix: one of l L
long-long-suffix: one of ll LL
character-literal: ' c-char-sequence ' u' c-char-sequence ' U' c-char-sequence ' L' c-char-sequence '
c-char-sequence: c-char c-char-sequence c-char
c-char: any member of the source character set except the single-quote ', backslash \, or new-line character escape-sequence universal-character-name
escape-sequence: simple-escape-sequence octal-escape-sequence hexadecimal-escape-sequence
simple-escape-sequence: one of \' \" \? \\ \a \b \f \n \r \t \v
octal-escape-sequence: \ octal-digit \ octal-digit octal-digit \ octal-digit octal-digit octal-digit
hexadecimal-escape-sequence: \x hexadecimal-digit hexadecimal-escape-sequence hexadecimal-digit
floating-literal: fractional-constant exponent-partopt floating-suffixopt digit-sequence exponent-part floating-suffixopt
fractional-constant: digit-sequenceopt . digit-sequence digit-sequence .
exponent-part: e signopt digit-sequence E signopt digit-sequence
sign: one of + -
digit-sequence: digit digit-sequence digit
floating-suffix: one of f l F L
string-literal: encoding-prefixopt " s-char-sequenceopt " encoding-prefixopt R raw-string
encoding-prefix: u8 u U L
s-char-sequence: s-char s-char-sequence s-char
s-char: any member of the source character set except the double-quote ", backslash \, or new-line character escape-sequence universal-character-name
raw-string: " d-char-sequenceopt ( r-char-sequenceopt ) d-char-sequenceopt "
r-char-sequence: r-char r-char-sequence r-char
r-char: any member of the source character set, except a right parenthesis ) followed by the initial d-char-sequence (which may be empty) followed by a double quote ".
d-char-sequence: d-char d-char-sequence d-char
d-char: any member of the basic source character set except: space, the left parenthesis (, the right parenthesis ), the backslash \, and the control characters representing horizontal tab, vertical tab, form feed, and newline.
boolean-literal: false true
pointer-literal: nullptr
user-defined-literal: user-defined-integer-literal user-defined-floating-literal user-defined-string-literal user-defined-character-literal
user-defined-integer-literal: decimal-literal ud-suffix octal-literal ud-suffix hexadecimal-literal ud-suffix
user-defined-floating-literal: fractional-constant exponent-partopt ud-suffix digit-sequence exponent-part ud-suffix
user-defined-string-literal: string-literal ud-suffix
user-defined-character-literal: character-literal ud-suffix
ud-suffix: identifier
translation-unit: declaration-seqopt
primary-expression: literal this ( expression ) id-expression lambda-expression
id-expression: unqualified-id qualified-id
unqualified-id: identifier operator-function-id conversion-function-id literal-operator-id ~ class-name ~ decltype-specifier template-id
qualified-id: nested-name-specifier templateopt unqualified-id :: identifier :: operator-function-id :: literal-operator-id :: template-id
nested-name-specifier: ::opt type-name :: ::opt namespace-name :: decltype-specifier :: nested-name-specifier identifier :: nested-name-specifier templateopt simple-template-id ::
lambda-expression: lambda-introducer lambda-declaratoropt compound-statement
lambda-introducer: [ lambda-captureopt ]
lambda-capture: capture-default capture-list capture-default , capture-list
capture-default: & =
capture-list: capture ...opt capture-list , capture ...opt
capture: identifier & identifier this
lambda-declarator: ( parameter-declaration-clause ) mutableopt exception-specificationopt attribute-specifier-seqopt trailing-return-typeopt
postfix-expression: primary-expression postfix-expression [ expression ] postfix-expression [ braced-init-list ] postfix-expression ( expression-listopt ) simple-type-specifier ( expression-listopt ) typename-specifier ( expression-listopt ) simple-type-specifier braced-init-list typename-specifier braced-init-list postfix-expression . templateopt id-expression postfix-expression -> templateopt id-expression postfix-expression . pseudo-destructor-name postfix-expression -> pseudo-destructor-name postfix-expression ++ postfix-expression -- dynamic_cast < type-id > ( expression ) static_cast < type-id > ( expression ) reinterpret_cast < type-id > ( expression ) const_cast < type-id > ( expression ) typeid ( expression ) typeid ( type-id )
expression-list: initializer-list
pseudo-destructor-name: nested-name-specifieropt type-name :: ~ type-name nested-name-specifier template simple-template-id :: ~ type-name nested-name-specifieropt ~ type-name ~ decltype-specifier
unary-expression: postfix-expression ++ cast-expression -- cast-expression unary-operator cast-expression sizeof unary-expression sizeof ( type-id ) sizeof ... ( identifier ) alignof ( type-id ) noexcept-expression new-expression delete-expression
unary-operator: one of * & + - ! ~
new-expression: ::opt new new-placementopt new-type-id new-initializeropt ::opt new new-placementopt ( type-id ) new-initializeropt
new-placement: ( expression-list )
new-type-id: type-specifier-seq new-declaratoropt
new-declarator: ptr-operator new-declaratoropt noptr-new-declarator
noptr-new-declarator: [ expression ] attribute-specifier-seqopt noptr-new-declarator [ constant-expression ] attribute-specifier-seqopt
new-initializer: ( expression-listopt ) braced-init-list
delete-expression: ::opt delete cast-expression ::opt delete [ ] cast-expression
noexcept-expression: noexcept ( expression )
cast-expression: unary-expression ( type-id ) cast-expression
pm-expression: cast-expression pm-expression .* cast-expression pm-expression ->* cast-expression
multiplicative-expression: pm-expression multiplicative-expression * pm-expression multiplicative-expression / pm-expression multiplicative-expression % pm-expression
additive-expression: multiplicative-expression additive-expression + multiplicative-expression additive-expression - multiplicative-expression
shift-expression: additive-expression shift-expression << additive-expression shift-expression >> additive-expression
relational-expression: shift-expression relational-expression < shift-expression relational-expression > shift-expression relational-expression <= shift-expression relational-expression >= shift-expression
equality-expression: relational-expression equality-expression == relational-expression equality-expression != relational-expression
and-expression: equality-expression and-expression & equality-expression
exclusive-or-expression: and-expression exclusive-or-expression ^ and-expression
inclusive-or-expression: exclusive-or-expression inclusive-or-expression | exclusive-or-expression
logical-and-expression: inclusive-or-expression logical-and-expression && inclusive-or-expression
logical-or-expression: logical-and-expression logical-or-expression || logical-and-expression
conditional-expression: logical-or-expression logical-or-expression ? expression : assignment-expression
assignment-expression: conditional-expression logical-or-expression assignment-operator initializer-clause throw-expression
assignment-operator: one of = *= /= %= += -= >>= <<= &= ^= |=
expression: assignment-expression expression , assignment-expression
constant-expression: conditional-expression
statement: labeled-statement attribute-specifier-seqopt expression-statement attribute-specifier-seqopt compound-statement attribute-specifier-seqopt selection-statement attribute-specifier-seqopt iteration-statement attribute-specifier-seqopt jump-statement declaration-statement attribute-specifier-seqopt try-block
labeled-statement: attribute-specifier-seqopt identifier : statement attribute-specifier-seqopt case constant-expression : statement attribute-specifier-seqopt default : statement
expression-statement: expressionopt ;
compound-statement: { statement-seqopt }
statement-seq: statement statement-seq statement
selection-statement: if ( condition ) statement if ( condition ) statement else statement switch ( condition ) statement
condition: expression attribute-specifier-seqopt decl-specifier-seq declarator = initializer-clause attribute-specifier-seqopt decl-specifier-seq declarator braced-init-list
iteration-statement: while ( condition ) statement do statement while ( expression ) ; for ( for-init-statement conditionopt ; expressionopt ) statement for ( for-range-declaration : for-range-initializer ) statement
for-init-statement: expression-statement simple-declaration
for-range-declaration: attribute-specifier-seqopt decl-specifier-seq declarator
for-range-initializer: expression braced-init-list
jump-statement: break ; continue ; return expressionopt ; return braced-init-list ; goto identifier ;
declaration-statement: block-declaration
declaration-seq: declaration declaration-seq declaration
declaration: block-declaration function-definition template-declaration explicit-instantiation explicit-specialization linkage-specification namespace-definition empty-declaration attribute-declaration
block-declaration: simple-declaration asm-definition namespace-alias-definition using-declaration using-directive static_assert-declaration alias-declaration opaque-enum-declaration
alias-declaration: using identifier attribute-specifier-seqopt = type-id ;
simple-declaration: decl-specifier-seqopt init-declarator-listopt ; attribute-specifier-seq decl-specifier-seqopt init-declarator-list ;
static_assert-declaration: static_assert ( constant-expression , string-literal ) ;
empty-declaration: ;
attribute-declaration: attribute-specifier-seq ;
decl-specifier: storage-class-specifier type-specifier function-specifier friend typedef constexpr
decl-specifier-seq: decl-specifier attribute-specifier-seqopt decl-specifier decl-specifier-seq
storage-class-specifier: register static thread_local extern mutable
function-specifier: inline virtual explicit
typedef-name: identifier
type-specifier: trailing-type-specifier class-specifier enum-specifier
trailing-type-specifier: simple-type-specifier elaborated-type-specifier typename-specifier cv-qualifier
type-specifier-seq: type-specifier attribute-specifier-seqopt type-specifier type-specifier-seq
trailing-type-specifier-seq: trailing-type-specifier attribute-specifier-seqopt trailing-type-specifier trailing-type-specifier-seq
simple-type-specifier: nested-name-specifieropt type-name nested-name-specifier template simple-template-id char char16_t char32_t wchar_t bool short int long signed unsigned float double void auto decltype-specifier
type-name: class-name enum-name typedef-name simple-template-id
decltype-specifier: decltype ( expression )
elaborated-type-specifier: class-key attribute-specifier-seqopt nested-name-specifieropt identifier class-key nested-name-specifieropt templateopt simple-template-id enum nested-name-specifieropt identifier
enum-name: identifier
enum-specifier: enum-head { enumerator-listopt } enum-head { enumerator-list , }
enum-head: enum-key attribute-specifier-seqopt identifieropt enum-baseopt enum-key attribute-specifier-seqopt nested-name-specifier identifier enum-baseopt
opaque-enum-declaration: enum-key attribute-specifier-seqopt identifier enum-baseopt ;
enum-key: enum enum class enum struct
enum-base: : type-specifier-seq
enumerator-list: enumerator-definition enumerator-list , enumerator-definition
enumerator-definition: enumerator enumerator = constant-expression
enumerator: identifier
namespace-name: original-namespace-name namespace-alias
original-namespace-name: identifier
namespace-definition: named-namespace-definition unnamed-namespace-definition
named-namespace-definition: original-namespace-definition extension-namespace-definition
original-namespace-definition: inlineopt namespace identifier { namespace-body }
extension-namespace-definition: inlineopt namespace original-namespace-name { namespace-body }
unnamed-namespace-definition: inlineopt namespace { namespace-body }
namespace-body: declaration-seqopt
namespace-alias: identifier
namespace-alias-definition: namespace identifier = qualified-namespace-specifier ;
qualified-namespace-specifier: nested-name-specifieropt namespace-name
using-declaration: using typenameopt nested-name-specifier unqualified-id ; using :: unqualified-id ;
using-directive: attribute-specifier-seqopt using namespace nested-name-specifieropt namespace-name ;
asm-definition: asm ( string-literal ) ;
linkage-specification: extern string-literal { declaration-seqopt } extern string-literal declaration
attribute-specifier-seq: attribute-specifier-seqopt attribute-specifier
attribute-specifier: [ [ attribute-list ] ] alignment-specifier
alignment-specifier: alignas ( type-id ...opt ) alignas ( alignment-expression ...opt )
attribute-list: attributeopt attribute-list , attributeopt attribute ... attribute-list , attribute ...
attribute: attribute-token attribute-argument-clauseopt
attribute-token: identifier attribute-scoped-token
attribute-scoped-token: attribute-namespace :: identifier
attribute-namespace: identifier
attribute-argument-clause: ( balanced-token-seq )
balanced-token-seq: balanced-tokenopt balanced-token-seq balanced-token
balanced-token: ( balanced-token-seq ) [ balanced-token-seq ] { balanced-token-seq } any token other than a parenthesis, a bracket, or a brace
init-declarator-list: init-declarator init-declarator-list , init-declarator
init-declarator: declarator initializeropt
declarator: ptr-declarator noptr-declarator parameters-and-qualifiers trailing-return-type
ptr-declarator: noptr-declarator ptr-operator ptr-declarator
noptr-declarator: declarator-id attribute-specifier-seqopt noptr-declarator parameters-and-qualifiers noptr-declarator [ constant-expressionopt ] attribute-specifier-seqopt ( ptr-declarator )
parameters-and-qualifiers: ( parameter-declaration-clause ) attribute-specifier-seqopt cv-qualifier-seqopt ref-qualifieropt exception-specificationopt
trailing-return-type: -> trailing-type-specifier-seq abstract-declaratoropt
ptr-operator: * attribute-specifier-seqopt cv-qualifier-seqopt & attribute-specifier-seqopt && attribute-specifier-seqopt nested-name-specifier * attribute-specifier-seqopt cv-qualifier-seqopt
cv-qualifier-seq: cv-qualifier cv-qualifier-seqopt
cv-qualifier: const volatile
ref-qualifier: & &&
declarator-id: ...opt id-expression nested-name-specifieropt class-name
type-id: type-specifier-seq abstract-declaratoropt
abstract-declarator: ptr-abstract-declarator noptr-abstract-declaratoropt parameters-and-qualifiers trailing-return-type abstract-pack-declarator
ptr-abstract-declarator: noptr-abstract-declarator ptr-operator ptr-abstract-declaratoropt
noptr-abstract-declarator: noptr-abstract-declaratoropt parameters-and-qualifiers noptr-abstract-declaratoropt [ constant-expressionopt ] attribute-specifier-seqopt ( ptr-abstract-declarator )
abstract-pack-declarator: noptr-abstract-pack-declarator ptr-operator abstract-pack-declarator
noptr-abstract-pack-declarator: noptr-abstract-pack-declarator parameters-and-qualifiers noptr-abstract-pack-declarator [ constant-expressionopt ] attribute-specifier-seqopt ...
parameter-declaration-clause: parameter-declaration-listopt ...opt parameter-declaration-list , ...
parameter-declaration-list: parameter-declaration parameter-declaration-list , parameter-declaration
parameter-declaration: attribute-specifier-seqopt decl-specifier-seq declarator attribute-specifier-seqopt decl-specifier-seq declarator = initializer-clause attribute-specifier-seqopt decl-specifier-seq abstract-declaratoropt attribute-specifier-seqopt decl-specifier-seq abstract-declaratoropt = initializer-clause
function-definition: attribute-specifier-seqopt decl-specifier-seqopt declarator virt-specifier-seqopt function-body
function-body:
ctor-initializeropt compound-statement
function-try-block
= default ;
= delete ;initializer: brace-or-equal-initializer ( expression-list )
brace-or-equal-initializer: = initializer-clause braced-init-list
initializer-clause: assignment-expression braced-init-list
initializer-list: initializer-clause ...opt initializer-list , initializer-clause ...opt
braced-init-list: { initializer-list ,opt } { }
class-name: identifier simple-template-id
class-specifier: class-head { member-specificationopt }
class-head: class-key attribute-specifier-seqopt class-head-name class-virt-specifieropt base-clauseopt class-key attribute-specifier-seqopt base-clauseopt
class-head-name: nested-name-specifieropt class-name
class-virt-specifier: final
class-key: class struct union
member-specification: member-declaration member-specificationopt access-specifier : member-specificationopt
member-declaration: attribute-specifier-seqopt decl-specifier-seqopt member-declarator-listopt ; function-definition ;opt using-declaration static_assert-declaration template-declaration alias-declaration
member-declarator-list: member-declarator member-declarator-list , member-declarator
member-declarator: declarator virt-specifier-seqopt pure-specifieropt declarator brace-or-equal-initializeropt identifieropt attribute-specifier-seqopt : constant-expression
virt-specifier-seq: virt-specifier virt-specifier-seq virt-specifier
virt-specifier: override final
pure-specifier: = 0
base-clause: : base-specifier-list
base-specifier-list: base-specifier ...opt base-specifier-list , base-specifier ...opt
base-specifier: attribute-specifier-seqopt base-type-specifier attribute-specifier-seqopt virtual access-specifieropt base-type-specifier attribute-specifier-seqopt access-specifier virtualopt base-type-specifier
class-or-decltype: nested-name-specifieropt class-name decltype-specifier
base-type-specifier: class-or-decltype
access-specifier: private protected public
conversion-function-id: operator conversion-type-id
conversion-type-id: type-specifier-seq conversion-declaratoropt
conversion-declarator: ptr-operator conversion-declaratoropt
ctor-initializer: : mem-initializer-list
mem-initializer-list: mem-initializer ...opt mem-initializer , mem-initializer-list ...opt
mem-initializer: mem-initializer-id ( expression-listopt ) mem-initializer-id braced-init-list
mem-initializer-id: class-or-decltype identifier
operator-function-id: operator operator
operator: one of new delete new[] delete[] + - * / % ^ & | ~ ! = < > += -= *= /= %= ^= &= |= << >> >>= <<= == != <= >= && || ++ -- , ->* -> ( ) [ ]
literal-operator-id: operator "" identifier
template-declaration: template < template-parameter-list > declaration
template-parameter-list: template-parameter template-parameter-list , template-parameter
template-parameter: type-parameter parameter-declaration
type-parameter: class ...opt identifieropt class identifieropt = type-id typename ...opt identifieropt typename identifieropt = type-id template < template-parameter-list > class ...opt identifieropt template < template-parameter-list > class identifieropt = id-expression
simple-template-id: template-name < template-argument-listopt >
template-id: simple-template-id operator-function-id < template-argument-listopt > literal-operator-id < template-argument-listopt >
template-name: identifier
template-argument-list: template-argument ...opt template-argument-list , template-argument ...opt
template-argument: constant-expression type-id id-expression
typename-specifier: typename nested-name-specifier identifier typename nested-name-specifier templateopt simple-template-id
explicit-instantiation: externopt template declaration
explicit-specialization: template < > declaration
try-block: try compound-statement handler-seq
function-try-block: try ctor-initializeropt compound-statement handler-seq
handler-seq: handler handler-seqopt
handler: catch ( exception-declaration ) compound-statement
exception-declaration: attribute-specifier-seqopt type-specifier-seq declarator attribute-specifier-seqopt type-specifier-seq abstract-declaratoropt ...
throw-expression: throw assignment-expressionopt
exception-specification: dynamic-exception-specification noexcept-specification
dynamic-exception-specification: throw ( type-id-listopt )
type-id-list: type-id ...opt type-id-list , type-id ...opt
noexcept-specification: noexcept ( constant-expression ) noexcept
preprocessing-file: groupopt
group: group-part group group-part
group-part: if-section control-line text-line # non-directive
if-section: if-group elif-groupsopt else-groupopt endif-line
if-group: # if constant-expression new-line groupopt # ifdef identifier new-line groupopt # ifndef identifier new-line groupopt
elif-groups: elif-group elif-groups elif-group
elif-group: # elif constant-expression new-line groupopt
else-group: # else new-line groupopt
endif-line: # endif new-line
control-line: # include pp-tokens new-line # define identifier replacement-list new-line # define identifier lparen identifier-listopt ) replacement-list new-line # define identifier lparen ... ) replacement-list new-line # define identifier lparen identifier-list, ... ) replacement-list new-line # undef identifier new-line # line pp-tokens new-line # error pp-tokensopt new-line # pragma pp-tokensopt new-line # new-line
text-line: pp-tokensopt new-line
non-directive: pp-tokens new-line
lparen: a ( character not immediately preceded by white-space
identifier-list: identifier identifier-list , identifier
replacement-list: pp-tokensopt
pp-tokens: preprocessing-token pp-tokens preprocessing-token
new-line: the new-line character