std::underflow_error

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Diagnostics library
Exception handling
Exception handling failures
(until C++17)
(until C++17)
(C++11)(until C++17)
(until C++17)
Error codes
Error codes
Exception categories
underflow_error
System error support
(C++11)
(C++11)
Assertions
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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).

cpp/error/exceptioncpp/error/runtime errorstd-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)
(3)
underflow_error( const underflow_error& other );
(until C++11)
underflow_error( const underflow_error& other ) noexcept;
(since C++11)
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

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