ps_mutable
ps->ps_mutable = NULL;
ps->ps_mutable = cp;
ps->ps_mutable = cp;
ps->ps_mutable = cp;
ocp = dst->ps_mutable;
dst->ps_mutable = cp;
ocp = dst->ps_mutable;
dst->ps_mutable = cp;
string->ps_mutable = str;
if ((ps->ps_flags & PS_F_NOCOPY) == 0 && ps->ps_mutable != NULL)
_PROP_FREE(ps->ps_mutable, M_PROP_STRING);