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 are constexpr: it is possible to create and use std::underflow_error objects in the evaluation of a constant expression.
However, std::underflow_error objects generally cannot be constexpr, because any dynamically allocated storage must be released in the same evaluation of constant expression.
Inheritance diagram
[edit] Member functions constructs a newunderflow_error object with the given message
underflow_error object
underflow_error( const char* what_arg );
(2) (constexpr since C++26)underflow_error( const underflow_error& other );
(3) (noexcept since C++11)Constructs the exception object with
what_argas explanatory string. After construction,
std::strcmp(what(), what_arg.c_str()) == 0.
2)Constructs the exception object with
what_argas explanatory string. After construction,
std::strcmp(what(), what_arg) == 0.
3)Copy constructor. If
*thisand
otherboth have dynamic type
std::underflow_error
then
std::strcmp(what(), other.what()) == 0. No exception can be thrown from the copy constructor.
Parameters what_arg - explanatory string other - another exception object to copy Exceptions NotesBecause 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.
Before the resolution of LWG issue 254, the non-copy constructor can only accept std::string. It makes dynamic allocation mandatory in order to construct a std::string object.
After the resolution of LWG issue 471, a derived standard exception class must have a publicly accessible copy constructor. It can be implicitly defined as long as the explanatory strings obtained by what() are the same for the original object and the copied object.
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. No exception can be thrown from the copy assignment operator.
*this
NotesAfter the resolution of LWG issue 471, a derived standard exception class must have a publicly accessible copy assignment operator. It can be implicitly defined as long as the explanatory strings obtained by what() are the same for the original object and the copied object.
std::exception) [edit] returns an explanatory string
std::exception) [edit] [edit] Notes [edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 254 C++98 the constructor accepting const char* was missing added LWG 471 C++98 the explanatory strings ofstd::underflow_error's
std::underflow_error object
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4