头文件循环include

a.hrl

-ifndef(DEFINE_a_HRL).
-define(DEFINE_a_HRL, true).

-include("b.hrl").

-define(a, a).
-endif.

b.hrl

-ifndef(DEFINE_b_HRL).
-define(DEFINE_b_HRL, true).

-include("a.hrl").

-define(b, b).


-endif.

main.erl

-module(main).
-export([start/0]).

start() ->
    main1:start(),
    main2:start(),
    main3:start(),
    ok.

main1.erl

-module(main1).

-include("a.hrl").

-export([start/0]).


start() ->
    io:format("~p ~p~n", [?a, ?b]).

main2.erl

-module(main2).

-include("a.hrl").
-include("b.hrl").
-export([start/0]).


start() ->
    io:format("~p ~p~n", [?a, ?b]).

main3.erl

-module(main3).


-include("b.hrl").
-export([start/0]).


start() ->
    io:format("~p ~p~n", [?a, ?b]).