callback for tracing instruction

callback for tracing memory access (READ or WRITE)

* decimal-literal: * '0' * nonzero-digit digit-sequence_opt * integer-part fractional-part * fractional-part * integer-p

* positional: * _empty_ * '-' * '-' decimal-literal * !'-' anything */

Getter that returns true for user-supplied options. Returns false if not * user-supplied, even with a default value. */

Print help message

* @throws std::runtime_error in case of any invalid argument */

Printing the one and only help message I've stuck with a simple message format, nothing fancy.