(cffi:defcstruct param-spec-string
  (:parent-instance (:pointer (:struct param-spec)))
  (:default-value (:string :free-to-foreign nil :free-from-foreign nil))
  (:cset-first (:string :free-to-foreign nil :free-from-foreign nil))
  (:cset-nth (:string :free-to-foreign nil :free-from-foreign nil))
  (:substitutor :char)
  (:flags-for-null :uint))  

:parent-instance

Private g:param-spec portion.

:default-value

The string with the default value.

:cset-frist

The string containing the allowed values for the first byte.

:cset-nth

The string containing the allowed values for the subsequent bytes.

:substitutor

The character with the replacement byte for bytes which do not match :cset-first or cset-nth.

:flags-for-null

The unsigned integer whether to replace empty string by nil and nil strings by an empty string.