33 Thread support library [thread]

33.6 Futures [futures]

33.6.4 Class future_­error [futures.future_error]

namespace std {
  class future_error : public logic_error {
  public:
    explicit future_error(future_errc e);

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

  private:
    error_code ec_;             // exposition only
  };
}
explicit future_error(future_errc e);
Effects: Constructs an object of class future_­error and initializes ec_­ with make_­error_­code(e).
const error_code& code() const noexcept;
Returns: ec_­.
const char* what() const noexcept;
Returns: An ntbs incorporating code().message().