std::underflow_error (3) - Linux Man Pages
Defined in header <stdexcept>
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).
constructor (public member function)
explicit underflow_error( const std::string& what_arg ); (1)
explicit underflow_error( const char* what_arg ); (2) (since C++11)
Constructs the exception object with what_arg as explanatory string that can be accessed through what().
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.
what_arg - explanatory string
May throw std::bad_alloc
Inherited from std::exception
destructor destroys the exception object
what returns an explanatory string