See also std::numeric_limits interface.
Limits of core language integer types |
|
Defined in header <climits> |
|
|---|---|
| CHAR_BIT | number of bits in a byte (macro constant) |
| MB_LEN_MAX | maximum number of bytes in a multibyte character (macro constant) |
| CHAR_MIN | minimum value of char (macro constant) |
| CHAR_MAX | maximum value of char (macro constant) |
| SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN
(C++11) | minimum value of signed char, short, int, long and long long respectively (macro constant) |
| SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX
(C++11) | maximum value of signed char, short, int, long and long long respectively (macro constant) |
| UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX
(C++11) | maximum value of unsigned char, unsigned short, unsigned int, unsigned long and unsigned long long respectively (macro constant) |
Defined in header <cwchar> |
|
Defined in header <cstdint> |
|
| WCHAR_MIN
(C++11) | minimum value of wchar_t (macro constant) |
| WCHAR_MAX
(C++11) | maximum value of wchar_t (macro constant) |
Limits of library type aliases |
|
Defined in header <cstdint> |
|
| PTRDIFF_MIN
(C++11) | minimum value of std::ptrdiff_t (macro constant) |
| PTRDIFF_MAX
(C++11) | maximum value of std::ptrdiff_t (macro constant) |
| SIZE_MAX
(C++11) | maximum value of std::size_t (macro constant) |
| SIG_ATOMIC_MIN
(C++11) | minimum value of std::sig_atomic_t (macro constant) |
| SIG_ATOMIC_MAX
(C++11) | maximum value of std::sig_atomic_t (macro constant) |
| WINT_MIN
(C++11) | minimum value of std::wint_t (macro constant) |
| WINT_MAX
(C++11) | maximum value of std::wint_t (macro constant) |
The types of these constants, other than CHAR_BIT and MB_LEN_MAX, are required to match the results of the integral promotions as applied to objects of the types they describe: CHAR_MAX may have type int or unsigned int, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.
A freestanding implementation may lack std::sig_atomic_t and/or std::wint_t typedef names, in which case the SIG_ATOMIC_* and/or WINT_* macros are correspondingly absent.
#include <climits>
#include <cstdint>
#include <iomanip>
#include <iostream>
int main()
{
constexpr int w = 14;
std::cout << std::left;
# define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n'
COUT( CHAR_BIT );
COUT( MB_LEN_MAX );
COUT( CHAR_MIN );
COUT( CHAR_MAX );
COUT( SCHAR_MIN );
COUT( SHRT_MIN );
COUT( INT_MIN );
COUT( LONG_MIN );
COUT( LLONG_MIN );
COUT( SCHAR_MAX );
COUT( SHRT_MAX );
COUT( INT_MAX );
COUT( LONG_MAX );
COUT( LLONG_MAX );
COUT( UCHAR_MAX );
COUT( USHRT_MAX );
COUT( UINT_MAX );
COUT( ULONG_MAX );
COUT( ULLONG_MAX );
COUT( PTRDIFF_MIN );
COUT( PTRDIFF_MAX );
COUT( SIZE_MAX );
COUT( SIG_ATOMIC_MIN );
COUT( SIG_ATOMIC_MAX );
COUT( WCHAR_MIN );
COUT( WCHAR_MAX );
COUT( WINT_MIN );
COUT( WINT_MAX );
}Possible output:
CHAR_BIT = 8 MB_LEN_MAX = 16 CHAR_MIN = -128 CHAR_MAX = 127 SCHAR_MIN = -128 SHRT_MIN = -32768 INT_MIN = -2147483648 LONG_MIN = -9223372036854775808 LLONG_MIN = -9223372036854775808 SCHAR_MAX = 127 SHRT_MAX = 32767 INT_MAX = 2147483647 LONG_MAX = 9223372036854775807 LLONG_MAX = 9223372036854775807 UCHAR_MAX = 255 USHRT_MAX = 65535 UINT_MAX = 4294967295 ULONG_MAX = 18446744073709551615 ULLONG_MAX = 18446744073709551615 PTRDIFF_MIN = -9223372036854775808 PTRDIFF_MAX = 9223372036854775807 SIZE_MAX = 18446744073709551615 SIG_ATOMIC_MIN = -2147483648 SIG_ATOMIC_MAX = 2147483647 WCHAR_MIN = -2147483648 WCHAR_MAX = 2147483647 WINT_MIN = 0 WINT_MAX = 4294967295
Defined in header <cfloat> |
|
|---|---|
| FLT_RADIX | the radix (integer base) used by the representation of all three floating-point types (macro constant) |
| DECIMAL_DIG
(C++11) | conversion from long double to decimal with at least DECIMAL_DIG digits and back to long double is the identity conversion: this is the decimal precision required to serialize/deserialize a long double (see also std::numeric_limits::max_digits10) (macro constant) |
| FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG
(C++17) | conversion from float/double/long double to decimal with at least FLT_DECIMAL_DIG/DBL_DECIMAL_DIG/LDBL_DECIMAL_DIG digits and back is the identity conversion: this is the decimal precision required to serialize/deserialize a floating-point value (see also std::numeric_limits::max_digits10). Defined to at least 6, 10, and 10 respectively, or 9 for IEEE float and 17 for IEEE double. (macro constant) |
| FLT_MINDBL_MINLDBL_MIN | minimum normalized positive value of float, double and long double respectively (macro constant) |
| FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN
(C++17) | minimum positive value of float, double and long double respectively (macro constant) |
| FLT_MAXDBL_MAXLDBL_MAX | maximum finite value of float, double and long double respectively (macro constant) |
| FLT_EPSILONDBL_EPSILONLDBL_EPSILON | difference between 1.0 and the next representable value for float, double and long double respectively (macro constant) |
| FLT_DIGDBL_DIGLDBL_DIG | number of decimal digits that are guaranteed to be preserved in text → float/double/long double → text roundtrip without change due to rounding or overflow (see std::numeric_limits::digits10 for explanation) (macro constant) |
| FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG | number of base FLT_RADIX digits that can be represented without losing precision for float, double and long double respectively (macro constant) |
| FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP | minimum negative integer such that FLT_RADIX raised by power one less than that integer is a normalized float, double and long double respectively (macro constant) |
| FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP | minimum negative integer such that 10 raised to that power is a normalized float, double and long double respectively (macro constant) |
| FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP | maximum positive integer such that FLT_RADIX raised by power one less than that integer is a representable finite float, double and long double respectively (macro constant) |
| FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP | maximum positive integer such that 10 raised to that power is a representable finite float, double and long double respectively (macro constant) |
| default rounding mode of floating-point arithmetic (macro constant) |
|
|
(C++11) | specifies in what precision all arithmetic operations are done (macro constant) |
| FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM
(C++17) | specifies whether the type supports subnormal (denormal) numbers:-1 – indeterminable, 0 – absent, 1 – present (macro constant) |
#include <cfloat>
#include <iomanip>
#include <iostream>
int main()
{
int w = 16;
std::cout << std::left; // std::cout << std::setprecision(53);
# define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n'
COUT( FLT_RADIX );
COUT( DECIMAL_DIG );
COUT( FLT_DECIMAL_DIG );
COUT( DBL_DECIMAL_DIG );
COUT( LDBL_DECIMAL_DIG );
COUT( FLT_MIN );
COUT( DBL_MIN );
COUT( LDBL_MIN );
COUT( FLT_TRUE_MIN );
COUT( DBL_TRUE_MIN );
COUT( LDBL_TRUE_MIN );
COUT( FLT_MAX );
COUT( DBL_MAX );
COUT( LDBL_MAX );
COUT( FLT_EPSILON );
COUT( DBL_EPSILON );
COUT( LDBL_EPSILON );
COUT( FLT_DIG );
COUT( DBL_DIG );
COUT( LDBL_DIG );
COUT( FLT_MANT_DIG );
COUT( DBL_MANT_DIG );
COUT( LDBL_MANT_DIG );
COUT( FLT_MIN_EXP );
COUT( DBL_MIN_EXP );
COUT( LDBL_MIN_EXP );
COUT( FLT_MIN_10_EXP );
COUT( DBL_MIN_10_EXP );
COUT( LDBL_MIN_10_EXP );
COUT( FLT_MAX_EXP );
COUT( DBL_MAX_EXP );
COUT( LDBL_MAX_EXP );
COUT( FLT_MAX_10_EXP );
COUT( DBL_MAX_10_EXP );
COUT( LDBL_MAX_10_EXP );
COUT( FLT_ROUNDS );
COUT( FLT_EVAL_METHOD );
COUT( FLT_HAS_SUBNORM );
COUT( DBL_HAS_SUBNORM );
COUT( LDBL_HAS_SUBNORM );
}Possible output:
FLT_RADIX = 2 DECIMAL_DIG = 21 FLT_DECIMAL_DIG = 9 DBL_DECIMAL_DIG = 17 LDBL_DECIMAL_DIG = 21 FLT_MIN = 1.17549e-38 DBL_MIN = 2.22507e-308 LDBL_MIN = 3.3621e-4932 FLT_TRUE_MIN = 1.4013e-45 DBL_TRUE_MIN = 4.94066e-324 LDBL_TRUE_MIN = 3.6452e-4951 FLT_MAX = 3.40282e+38 DBL_MAX = 1.79769e+308 LDBL_MAX = 1.18973e+4932 FLT_EPSILON = 1.19209e-07 DBL_EPSILON = 2.22045e-16 LDBL_EPSILON = 1.0842e-19 FLT_DIG = 6 DBL_DIG = 15 LDBL_DIG = 18 FLT_MANT_DIG = 24 DBL_MANT_DIG = 53 LDBL_MANT_DIG = 64 FLT_MIN_EXP = -125 DBL_MIN_EXP = -1021 LDBL_MIN_EXP = -16381 FLT_MIN_10_EXP = -37 DBL_MIN_10_EXP = -307 LDBL_MIN_10_EXP = -4931 FLT_MAX_EXP = 128 DBL_MAX_EXP = 1024 LDBL_MAX_EXP = 16384 FLT_MAX_10_EXP = 38 DBL_MAX_10_EXP = 308 LDBL_MAX_10_EXP = 4932 FLT_ROUNDS = 1 FLT_EVAL_METHOD = 0 FLT_HAS_SUBNORM = 1 DBL_HAS_SUBNORM = 1 LDBL_HAS_SUBNORM = 1
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 416 | C++98 | it was unclear whether the types of the macros in <climits> are guaranteedto match the type to which they refer (C++ refers to C, and C says no) | clarified as not guaranteed |
| C documentation for Numeric limits |
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