WithProper = code:lib_dir(proper) /= {error, bad_name}.

ErlOpts =
    [debug_info] ++
    case WithProper of
        true ->
            [{d, 'WITH_PROPER'}];
        false ->
            []
    end,

[{port_specs, [
    {"priv/hqueue.so", ["c_src/hqueue*.c"]}
]},
{port_env, [
    {".*", "CFLAGS", "$CFLAGS -g -Wall -Werror -DHQ_ENIF_ALLOC -O3"}
    %% {".*", "CFLAGS", "$CFLAGS -g -Wall -Werror -Wextra"}
]},
{eunit_opts, [verbose]},
{erl_opts, [{i, "../"} | ErlOpts]}].