5 Lexical conventions [lex]

5.13 Literals [lex.literal]

5.13.3 Character literals [lex.ccon]

_{o p t}

' c-char-sequence '

encoding-prefix: one of
u8 u U L

c-char-sequence:
c-char
c-char-sequence c-char

c-char:
basic-c-char
escape-sequence
universal-character-name

basic-c-char:
any member of the translation character set except the U+0027 apostrophe,
U+005c reverse solidus, or new-line character

escape-sequence:
simple-escape-sequence
numeric-escape-sequence
conditional-escape-sequence

simple-escape-sequence:
\ simple-escape-sequence-char

simple-escape-sequence-char: one of
' " ? \ a b f n r t v

numeric-escape-sequence:
octal-escape-sequence
hexadecimal-escape-sequence

simple-octal-digit-sequence:
octal-digit
simple-octal-digit-sequence octal-digit

octal-escape-sequence:
\ octal-digit
\ octal-digit octal-digit
\ octal-digit octal-digit octal-digit
\o{ simple-octal-digit-sequence }

hexadecimal-escape-sequence:
\x simple-hexadecimal-digit-sequence
\x{ simple-hexadecimal-digit-sequence }

conditional-escape-sequence:
\ conditional-escape-sequence-char

conditional-escape-sequence-char:
any member of the basic character set that is not an octal-digit, a simple-escape-sequence-char, or the characters N, o, u, U, or x

A non-encodable character literal is a character-literal whose c-char-sequence consists of a single c-char that is not a numeric-escape-sequence and that specifies a character that either lacks representation in the literal's associated character encoding or that cannot be encoded as a single code unit.

A multicharacter literal is a character-literal whose c-char-sequence consists of more than one c-char.

The encoding-prefix of a non-encodable character literal or a multicharacter literal shall be absent.

Such character-literals are conditionally-supported.

The kind of a character-literal, its type, and its associated character encoding ([lex.charset]) are determined by its encoding-prefix and its c-char-sequence as defined by Table 9 .

The special cases for non-encodable character literals and multicharacter literals take precedence over the base kind.

[Note 1:

The associated character encoding for ordinary character literals determines encodability, but does not determine the value of non-encodable ordinary character literals or ordinary multicharacter literals.

The examples in Table 9 for non-encodable ordinary character literals assume that the specified character lacks representation in the ordinary literal encoding or that encoding the character would require more than one code unit.

— end note]

Table 9: Character literals [tab:lex.ccon.literal]

🔗	Encoding	Kind	Type	Associated char-	Example
🔗	prefix			acter encoding
🔗	none	ordinary character literal	char	ordinary	'v'
🔗		non-encodable ordinary character literal	int	literal	'\U0001F525'
🔗		ordinary multicharacter literal	int	encoding	'abcd'
🔗	L	wide character literal	wchar_t	wide literal	L'w'
🔗				encoding
🔗	u8	UTF-8 character literal	char8_t	UTF-8	u8'x'
🔗	u	UTF-16 character literal	char16_t	UTF-16	u'y'
🔗	U	UTF-32 character literal	char32_t	UTF-32	U'z'

In translation phase 4, the value of a character-literal is determined using the range of representable values of the character-literal's type in translation phase 7.

A non-encodable character literal or a multicharacter literal has an implementation-defined value.

The value of any other kind of character-literal is determined as follows:

(3.1)
A character-literal with a c-char-sequence consisting of a single basic-c-char, simple-escape-sequence, or universal-character-name is the code unit value of the specified character as encoded in the literal's associated character encoding.

[Note 2:
If the specified character lacks representation in the literal's associated character encoding or if it cannot be encoded as a single code unit, then the literal is a non-encodable character literal.
— end note]
(3.2)
A character-literal with a c-char-sequence consisting of a single numeric-escape-sequence has a value as follows:
- (3.2.1)
  Let v be the integer value represented by the octal number comprising the sequence of octal-digits in an octal-escape-sequence or by the hexadecimal number comprising the sequence of hexadecimal-digits in a hexadecimal-escape-sequence.
- (3.2.2)
  If v does not exceed the range of representable values of the character-literal's type, then the value is v.
- (3.2.3)
  Otherwise, if the character-literal's encoding-prefix is absent or L, and v does not exceed the range of representable values of the corresponding unsigned type for the underlying type of the character-literal's type, then the value is the unique value of the character-literal's type T that is congruent to v modulo $2^{N}$ , where N is the width of T.
- (3.2.4)
  Otherwise, the character-literal is ill-formed.
(3.3)
A character-literal with a c-char-sequence consisting of a single conditional-escape-sequence is conditionally-supported and has an implementation-defined value.

The character specified by a simple-escape-sequence is specified in Table 10 .

[Note 3:

Using an escape sequence for a question mark is supported for compatibility with ISO C++ 2014 and ISO C.

— end note]

Table 10: Simple escape sequences [tab:lex.ccon.esc]

🔗	character		*simple-escape-sequence*
🔗	U+000a	line feed	\n
🔗	U+0009	character tabulation	\t
🔗	U+000b	line tabulation	\v
🔗	U+0008	backspace	\b
🔗	U+000d	carriage return	\r
🔗	U+000c	form feed	\f
🔗	U+0007	alert	\a
🔗	U+005c	reverse solidus	\\
🔗	U+003f	question mark	\?
🔗	U+0027	apostrophe	\'
🔗	U+0022	quotation mark	\"