OFFTAB_MODE_READ
assert(offtab->ot_mode == OFFTAB_MODE_READ);
assert(offtab->ot_mode == OFFTAB_MODE_READ);
offtab->ot_mode = OFFTAB_MODE_READ;
assert(offtab->ot_mode == OFFTAB_MODE_READ);
assert(offtab->ot_mode == OFFTAB_MODE_READ);