5 Lexical conventions [lex]

5.13 Literals [lex.literal]

5.13.2 Integer literals [lex.icon]

integer-literal:
	binary-literal integer-suffix $_{o p t}$ 
	octal-literal integer-suffix $_{o p t}$ 
	decimal-literal integer-suffix $_{o p t}$ 
	hexadecimal-literal integer-suffix $_{o p t}$

binary-literal:
	0b binary-digit
	0B binary-digit
	binary-literal ' $_{o p t}$  binary-digit

octal-literal:
	0
	octal-literal ' $_{o p t}$  octal-digit

decimal-literal:
	nonzero-digit
	decimal-literal ' $_{o p t}$  digit

hexadecimal-literal:
	hexadecimal-prefix hexadecimal-digit-sequence

binary-digit: one of
	0  1

octal-digit: one of
	0  1  2  3  4  5  6  7

nonzero-digit: one of
	1  2  3  4  5  6  7  8  9

hexadecimal-prefix: one of
	0x  0X

hexadecimal-digit-sequence:
	hexadecimal-digit
	hexadecimal-digit-sequence ' $_{o p t}$  hexadecimal-digit

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-suffix $_{o p t}$  
	unsigned-suffix long-long-suffix $_{o p t}$  
	long-suffix unsigned-suffix $_{o p t}$  
	long-long-suffix unsigned-suffix $_{o p t}$

unsigned-suffix: one of
	u  U

long-suffix: one of
	l  L

long-long-suffix: one of
	ll  LL

In an integer-literal, the sequence of binary-digits, octal-digits, digits, or hexadecimal-digits is interpreted as a base N integer as shown in table Table 7; the lexically first digit of the sequence of digits is the most significant.

[ Note

The prefix and any optional separating single quotes are ignored when determining the value.

— end note

]

Table 7: Base of integer-literals [tab:lex.icon.base]

Kind of integer-literal	base N
binary-literal	2
octal-literal	8
decimal-literal	10
hexadecimal-literal	16

The hexadecimal-digits a through f and A through F have decimal values ten through fifteen.

[ Example

The number twelve can be written 12, 014, 0XC, or 0b1100.

The integer-literals 1048576, 1'048'576, 0X100000, 0x10'0000, and 0'004'000'000 all have the same value.

— end example

]

The type of an integer-literal is the first type in the list in Table 8 corresponding to its optional integer-suffix in which its value can be represented.

An integer-literal is a prvalue.

Table 8: Types of integer-literals [tab:lex.icon.type]

integer-suffix	decimal-literal	integer-literal other than decimal-literal
none	int	int
	long int	unsigned int
	long long int	long int
		unsigned long int
		long long int
		unsigned long long int
u or U	unsigned int	unsigned int
	unsigned long int	unsigned long int
	unsigned long long int	unsigned long long int
l or L	long int	long int
	long long int	unsigned long int
		long long int
		unsigned long long int
Both u or U	unsigned long int	unsigned long int
and l or L	unsigned long long int	unsigned long long int
ll or LL	long long int	long long int
		unsigned long long int
Both u or U	unsigned long long int	unsigned long long int
and ll or LL

If an integer-literal cannot be represented by any type in its list and an extended integer type ([basic.fundamental]) can represent its value, it may have that extended integer type.

If all of the types in the list for the integer-literal are signed, the extended integer type shall be signed.

If all of the types in the list for the integer-literal are unsigned, the extended integer type shall be unsigned.

If the list contains both signed and unsigned types, the extended integer type may be signed or unsigned.

A program is ill-formed if one of its translation units contains an integer-literal that cannot be represented by any of the allowed types.