30 Thread support library [thread]

30.6 Futures [futures]

30.6.3 Class future_error [futures.future_error]

namespace std {
  class future_error : public logic_error {
  public:
    future_error(error_code ec);  // exposition only

    const error_code& code() const noexcept;
    const char*       what() const noexcept;
  };
}

const error_code& code() const noexcept;

1

Returns: The value of ec that was passed to the object's constructor.

const char *what() const noexcept;

2

Returns: An ntbs incorporating code().message().