std::exception::operator= (3) Linux Manual Page

std::exception::operator= – std::exception::operator=

Synopsis

exception &operator=(const exception &other) throw();
(until C++ 11)

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

Copy assignment operator. Assigns the contents of other
The effects of calling what() after assignment are implementation-defined. (until C++11)
If *this and other both have dynamic type std::exception then std::strcmp(what(), other.what()) == 0. (since C++11)

Parameters

other – another exception to assign the contents of