NAME

std::underflow_error - std::underflow_error

Synopsis

Defined in header <stdexcept>
class underflow_error;

Defines a type of object to be thrown as exception. It may be used to report
arithmetic underflow errors (that is, situations where the result of a computation
is a subnormal floating-point value)

The standard library components do not throw this exception (mathematical functions
report underflow errors as specified in math_errhandling). Third-party libraries,
however, use this. For example, boost.math throws std::underflow_error if
boost::math::policies::throw_on_error is enabled (the default setting).

std-underflow error-inheritance.svg

Inheritance diagram

Member functions

constructor constructs a new underflow_error object with the given message
(public member function)
operator= replaces the underflow_error object
(public member function)
what returns the explanatory string
(public member function)

std::underflow_error::underflow_error

underflow_error( const std::string& what_arg ); (1)
underflow_error( const char* what_arg ); (2) (since C++11)
underflow_error( const underflow_error& other ); (until C++11)
underflow_error( const underflow_error& other ) (3) (since C++11)
noexcept;

1-2) Constructs the exception object with what_arg as explanatory string that can be
accessed through what().
3) Copy constructor.
If *this and other both have dynamic type std::underflow_error then
std::strcmp(what(), other.what()) == 0.
(since C++11)

Parameters

what_arg - explanatory string
other - another exception object to copy

Exceptions

1-2) May throw std::bad_alloc

Notes

Because copying std::underflow_error is not permitted to throw exceptions, this
message is typically stored internally as a separately-allocated reference-counted
string. This is also why there is no constructor taking std::string&&: it would have
to copy the content anyway.

std::underflow_error::operator=

underflow_error& operator=( const underflow_error& other ); (until C++11)
underflow_error& operator=( const underflow_error& other ) noexcept; (since C++11)

Assigns the contents with those of other.
If *this and other both have dynamic type std::underflow_error then
std::strcmp(what(), other.what()) == 0 after assignment.
(since C++11)

Parameters

other - another exception object to assign with

Return value

*this

std::underflow_error::what

virtual const char* what() const throw(); (until C++11)
virtual const char* what() const noexcept; (since C++11)

Returns the explanatory string.

Parameters

(none)

Return value

Pointer to a null-terminated string with explanatory information. The string is
suitable for conversion and display as a std::wstring. The pointer is guaranteed to
be valid at least until the exception object from which it is obtained is destroyed,
or until a non-const member function (e.g. copy assignment operator) on the
exception object is called.

Notes

Implementations are allowed but not required to override what().

Inherited from std::runtime_error

Inherited from std::exception

Member functions

destructor destroys the exception object
[virtual] (virtual public member function of std::exception)
what returns an explanatory string
[virtual] (virtual public member function of std::exception)