MIN_DLVL
prg, MIN_DLVL, MAX_DLVL, dlvl,
assert(MIN_DLVL == 0);
assert(MIN_DLVL == DNONE);
if (dlvl < MIN_DLVL || dlvl > MAX_DLVL) {
dlvl_t dlvl = MIN_DLVL; /* verbosity */