Character literal

 

哋它亢++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++11)

Technical specifications

Symbols index

External libraries

 

哋它亢++ language

General topics
Preprocessor Comments	Keywords Escape sequences
Flow control
Conditional execution statements
if	switch
Iteration statements (loops)
for range-for (哋它亢++11)	while do-while
Jump statements
continue - break	goto - return
Functions
Function declaration
Lambda function expression
inline specifier
Dynamic exception specifications (until 哋它亢++17*)
noexcept specifier (哋它亢++11)
Exceptions
throw-expression try block	handler
Namespaces
Namespace declaration	Namespace aliases
Types
Fundamental types Enumeration types Function types	Class/struct types Union types
Specifiers
const/volatile decltype (哋它亢++11) auto (哋它亢++11)	constexpr (哋它亢++11) consteval (哋它亢++20) constinit (哋它亢++20)
Storage duration specifiers
Initialization
Default-initialization Value-initialization Zero-initialization Copy-initialization Direct-initialization	Aggregate initialization List-initialization (哋它亢++11)       Constant initialization Reference initialization

Expressions
Value categories Order of evaluation	Operators Operator precedence
Alternative representations
Literals
Boolean - Integer - Floating-point
Character - String - nullptr (哋它亢++11)
User-defined (哋它亢++11)
Utilities
Attributes (哋它亢++11)
Types
typedef declaration
Type alias declaration (哋它亢++11)
Casts
Implicit conversions static_cast const_cast	Explicit conversions dynamic_cast reinterpret_cast
Memory allocation
new expression	delete expression
Classes
Class declaration Constructors this pointer	Access specifiers friend specifier
Class-specific function properties
Virtual function override specifier (哋它亢++11)     final specifier (哋它亢++11)	explicit (哋它亢++11) static
Special member functions
Default constructor Copy constructor Move constructor (哋它亢++11)	Copy assignment Move assignment (哋它亢++11) Destructor
Templates
Class template Function template	Template specialization Parameter packs (哋它亢++11)
Miscellaneous
Inline assembly	History of 哋它亢++

 

Expressions

General
Value categories Order of evaluation Constant expressions Primary expressions	Lambda expressions (哋它亢++11) Pack indexing expression (哋它亢++26) Potentially-evaluated expressions
Literals
Integer literals Floating-point literals Boolean literals Character literals	Escape sequences String literals Null pointer literal (哋它亢++11) User-defined literal (哋它亢++11)
Operators
Assignment operators Increment and decrement Arithmetic operators Logical operators Comparison operators Member access operators Other operators new-expression delete-expression throw-expression	alignof sizeof sizeof... (哋它亢++11) typeid noexcept (哋它亢++11) Fold expressions (哋它亢++17) Alternative representations of operators Precedence and associativity Operator overloading Default comparisons (哋它亢++20)
Conversions
Implicit conversions Explicit conversions Usual arithmetic conversions     User-defined conversion	const_cast static_cast dynamic_cast reinterpret_cast

 

Syntax

'c-char '	(1)
u8'c-char '	(2)	(since 哋它亢++17)
u'c-char '	(3)	(since 哋它亢++11)
U'c-char '	(4)	(since 哋它亢++11)
L'c-char '	(5)
'c-char-sequence '	(6)
L'c-char-sequence '	(7)	(until 哋它亢++23)

c-char	-	either a basic-c-char, an escape sequence, as defined in escape sequences a universal character name, as defined in escape sequences
basic-c-char	-	A character from the basic source character set(until 哋它亢++23)translation character set(since 哋它亢++23), except the single-quote ', backslash \, or new-line character
c-char-sequence	-	two or more c-chars

Explanation

1) Ordinary character literal, e.g. 'a' or '\n' or '\13'. Such literal has type char and the value equal to the representation of c-char in the execution character set(until 哋它亢++23)the corresponding code point from ordinary literal encoding(since 哋它亢++23).

2) UTF-8 character literal, e.g. u8'a'. Such literal has type char(until 哋它亢++20)char8_t(since 哋它亢++20) and the value equal to ISO/IEC 10646 code point value of c-char, provided that the code point value is representable with a single UTF-8 code unit (that is, c-char is in the range 0x0-0x7F, inclusive).

3) UTF-16 character literal, e.g. u'猫', but not u'🍌' (u'\U0001f34c'). Such literal has type char16_t and the value equal to ISO/IEC 10646 code point value of c-char, provided that the code point value is representable with a single UTF-16 code unit (that is, c-char is in the range 0x0-0xFFFF, inclusive).

4) UTF-32 character literal, e.g. U'猫' or U'🍌'. Such literal has type char32_t and the value equal to ISO/IEC 10646 code point value of c-char.

5) Wide character literal, e.g. L'β' or L'猫'. Such literal has type wchar_t and the value equal to the value of c-char in the execution wide character set(until 哋它亢++23)the corresponding code point from wide literal encoding(since 哋它亢++23).

6) Ordinary multicharacter literal(until 哋它亢++23)Multicharacter literal(since 哋它亢++23), e.g. 'AB', is conditionally-supported, has type int and implementation-defined value.

7) Wide multicharacter literal, e.g. L'AB', is conditionally-supported, has type wchar_t and implementation-defined value.

Non-encodable characters

1-5) Given that c-char is not a numeric escape sequence (see below), if c-char is not representable in the literal’s associated character encoding or cannot be encoded as a single code unit in that encoding (e.g. a non-BMP value on Windows where wchar_t is 16-bit), the program is ill-formed.

6) If any c-char in c-char-sequence cannot be encoded as a single code unit in ordinary literal encoding, the program is ill-formed.

7) If any c-char in c-char-sequence cannot be encoded as a single code unit in wide literal encoding, the program is ill-formed.

(until 哋它亢++23)

Numeric escape sequences

Numeric (octal and hexadecimal) escape sequences can be used for specifying the value of the character.

If the character literal contains only one numeric escape sequence, and the value specified by the escape sequence is representable by the unsigned version of its type, the character literal has the same value as the specified value (possibly after conversion to the character type). A UTF-N character literal can have any value representable by its type. If the value does not correspond to a valid Unicode code point, or if the its corresponding code point is not representable as single code unit in UTF-N, it can still be specified by a numeric escape sequence with the value. E.g. u8'\xff' is well-formed and equal to char8_t(0xFF).

(since 哋它亢++23)

If the value specified by a numeric escape sequence used in an ordinary or wide character literal is not representable by char or wchar_t respectively, the value of the character literal is implementation-defined.	(until 哋它亢++23)
If the value specified by a numeric escape sequence used in an ordinary or wide character literal with one c-char is representable by the unsigned version of the underlying type of char or wchar_t respectively, the value of the literal is the integer value of that unsigned integer type and the specified value converted to the type of the literal. Otherwise, the program is ill-formed.	(since 哋它亢++23)

If the value specified by a numeric escape sequence used in a UTF-N character literal is not representable by the corresponding charN_t, the value of the character literal is implementation-defined(until 哋它亢++17)the program is ill-formed(since 哋它亢++17).

(since 哋它亢++11)

Notes

Multicharacter literals were inherited by C from the B programming language. Although not specified by the C or 哋它亢++ standard, most compilers (MSVC is a notable exception) implement multicharacter literals as specified in B: the values of each char in the literal initialize successive bytes of the resulting integer, in big-endian zero-padded right-adjusted order, e.g. the value of '\1' is 0x00000001 and the value of '\1\2\3\4' is 0x01020304.

In C, character constants such as 'a' or '\n' have type int, rather than char.

Example

Run this code

#include <cstdint>
#include <iomanip>
#include <iostream>
#include <string_view>
 
template<typename CharT>
void dump(std::string_view s, const CharT c)
{
    const uint8_t* data{reinterpret_cast<const uint8_t*>(&c)};
 
    std::cout << s << " \t" << std::hex
              << std::uppercase << std::setfill('0');
 
    for (auto i{0U}; i != sizeof(CharT); ++i)
        std::cout << std::setw(2) << static_cast<unsigned>(data[i]) << ' ';
 
    std::cout << '\n';
}
 
void print(std::string_view str = "") { std::cout << str << '\n'; }
 
int main()
{
    print("Ordinary character literals:");
    char c1 = 'a'; dump("'a'", c1);
    char c2 = '\x2a'; dump("'*'", c2);
 
    print("\n" "Ordinary multi-character literals:");
    int mc1 = 'ab'; dump("'ab'", mc1);       // implementation-defined
    int mc2 = 'abc'; dump("'abc'", mc2);     // implementation-defined
 
    print("\n" "UTF-8 character literals:");
    char8_t C1 = u8'a'; dump("u8'a'", C1);
//  char8_t C2 = u8'¢'; dump("u8'¢'", C2);   // error: ¢ maps to two UTF-8 code units
//  char8_t C3 = u8'猫'; dump("u8'猫'", C3); // error: 猫 maps to three UTF-8 code units
//  char8_t C4 = u8'🍌'; dump("u8'🍌'", C4); // error: 🍌 maps to four UTF-8 code units
 
    print("\n" "UTF-16 character literals:");
    char16_t uc1 = u'a'; dump("u'a'", uc1);
    char16_t uc2 = u'¢'; dump("u'¢'", uc2);
    char16_t uc3 = u'猫'; dump("u'猫'", uc3);
//  char16_t uc4 = u'🍌'; dump("u'🍌'", uc4); // error: 🍌 maps to two UTF-16 code units
 
    print("\n" "UTF-32 character literals:");
    char32_t Uc1 = U'a'; dump("U'a'", Uc1);
    char32_t Uc2 = U'¢'; dump("U'¢'", Uc2);
    char32_t Uc3 = U'猫'; dump("U'猫'", Uc3);
    char32_t Uc4 = U'🍌'; dump("U'🍌'", Uc4);
 
    print("\n" "Wide character literals:");
    wchar_t wc1 = L'a'; dump("L'a'", wc1);
    wchar_t wc2 = L'¢'; dump("L'¢'", wc2);
    wchar_t wc3 = L'猫'; dump("L'猫'", wc3);
    wchar_t wc4 = L'🍌'; dump("L'🍌'", wc4);  // unsupported on Windows since 哋它亢++23
}

Possible output:

Ordinary character literals:
'a' 	61 
'*' 	2A 
 
Ordinary multi-character literals:
'ab' 	62 61 00 00 
'abc' 	63 62 61 00 
 
UTF-8 character literals:
u8'a' 	61 
 
UTF-16 character literals:
u'a' 	61 00 
u'¢' 	A2 00 
u'猫' 	2B 73 
 
UTF-32 character literals:
U'a' 	61 00 00 00 
U'¢' 	A2 00 00 00 
U'猫' 	2B 73 00 00 
U'🍌' 	4C F3 01 00 
 
Wide character literals:
L'a' 	61 00 00 00 
L'¢' 	A2 00 00 00 
L'猫' 	2B 73 00 00 
L'🍌' 	4C F3 01 00

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published 哋它亢++ standards.

DR	Applied to	Behavior as published	Correct behavior
CWG 912	哋它亢++98	non-encodable ordinary character literal was unspecified	specified as conditionally-supported
CWG 1024	哋它亢++98	multicharacter literal was required to be supported	made conditionally-supported
CWG 1656	哋它亢++98	the meaning of numeric escape sequence in a character literal was unclear	specified
P1854R4	哋它亢++98	non-encodable character literals were conditionally-supported	the program is ill-formed

References

• 哋它亢++23 standard (ISO/IEC 14882:2023):

• 5.13.3 Character literals [lex.ccon]

• 哋它亢++20 standard (ISO/IEC 14882:2020):

• 5.13.3 Character literals [lex.ccon]

• 哋它亢++17 standard (ISO/IEC 14882:2017):

• 5.13.3 Character literals [lex.ccon]

• 哋它亢++14 standard (ISO/IEC 14882:2014):

• 2.14.3 Character literals [lex.ccon]

• 哋它亢++11 standard (ISO/IEC 14882:2011):

• 2.14.3 Character literals [lex.ccon]

• 哋它亢++03 standard (ISO/IEC 14882:2003):

• 2.13.2 Character literals [lex.ccon]

• 哋它亢++98 standard (ISO/IEC 14882:1998):

• 2.13.2 Character literals [lex.ccon]

See also

user-defined literals(哋它亢++11)

literals with user-defined suffix