LNK2005 error when linking multiple projects that use boost

Question

I have a project that consists from one main project, 3 projects that use boost and few other projects that links to static libraries. These 3 projects use boost. But I can't build my main project. I've got a lot of error LNK2005: .... already defined in ... errors. As I understood, boost automaticaly links libraries to both of this projects. I tried to use BOOST_ALL_NO_LIB, but it didn't work. After adding this macro I've got unresolved symbols errors, but the redefinition errors still here. How can I solve this problem?

UPD1: there about 400+ errors. Here are first of them:

1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "unsigned long __cdecl boost::asio::detail::win_tss_ptr_create(void)" (?win_tss_ptr_create@detail@asio@boost@@YAKXZ) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "void __cdecl boost::asio::detail::do_throw_error(class boost::system::error_code const &,char const *)" (?do_throw_error@detail@asio@boost@@YAXABVerror_code@system@3@PBD@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "class boost::system::error_category const & __cdecl boost::asio::error::get_misc_category(void)" (?get_misc_category@error@asio@boost@@YAABVerror_category@system@3@XZ) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "protected: static void __cdecl boost::asio::detail::winsock_init_base::startup(struct boost::asio::detail::winsock_init_base::data &,unsigned char,unsigned char)" (?startup@winsock_init_base@detail@asio@boost@@KAXAAUdata@1234@EE@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "protected: static void __cdecl boost::asio::detail::winsock_init_base::cleanup(struct boost::asio::detail::winsock_init_base::data &)" (?cleanup@winsock_init_base@detail@asio@boost@@KAXAAUdata@1234@@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "protected: static void __cdecl boost::asio::detail::winsock_init_base::throw_on_error(struct boost::asio::detail::winsock_init_base::data &)" (?throw_on_error@winsock_init_base@detail@asio@boost@@KAXAAUdata@1234@@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "public: void __thiscall boost::asio::detail::win_iocp_io_service::post_deferred_completions(class boost::asio::detail::op_queue<class boost::asio::detail::win_iocp_operation> &)" (?post_deferred_completions@win_iocp_io_service@detail@asio@boost@@QAEXAAV?$op_queue@Vwin_iocp_operation@detail@asio@boost@@@234@@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "struct boost::asio::detail::signal_state * __cdecl boost::asio::detail::get_signal_state(void)" (?get_signal_state@detail@asio@boost@@YAPAUsignal_state@123@XZ) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: _boost_asio_signal_handler already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(VS_Project_with_boost_1.obj) : error LNK2005: "public: static void __cdecl boost::asio::detail::signal_set_service::deliver_signal(int)" (?deliver_signal@signal_set_service@detail@asio@boost@@SAXH@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(Some_file.obj) : error LNK2005: "unsigned long __cdecl boost::asio::detail::win_tss_ptr_create(void)" (?win_tss_ptr_create@detail@asio@boost@@YAKXZ) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(Some_file.obj) : error LNK2005: "void __cdecl boost::asio::detail::do_throw_error(class boost::system::error_code const &,char const *)" (?do_throw_error@detail@asio@boost@@YAXABVerror_code@system@3@PBD@Z) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(Some_file.obj) : error LNK2005: "class boost::system::error_category const & __cdecl boost::asio::error::get_misc_category(void)" (?get_misc_category@error@asio@boost@@YAABVerror_category@system@3@XZ) already defined in Project_with_boost_2.lib(asio.obj)
1>Project_with_boost_1.lib(Some_file.obj) : error LNK2005: "protected: static void __cdecl boost::asio::detail::winsock_init_base::startup(struct boost::asio::detail::winsock_init_base::data &,unsigned char,unsigned char)" (?startup@winsock_init_base@detail@asio@boost@@KAXAAUdata@1234@EE@Z) already defined in Project_with_boost_2.lib(asio.obj)

UPD2: I also tried to use macros kind of BOOST_SYSTEM_NO_LIB, BOOST_ASIO_NO_LIB. Result is the same as by using BOOST_ALL_NO_LIB

UPD3: I can set linker option in my main project "Force File Output" to "Multiply Defined Symbols Only /FORCE:MULTIPLE" and project compiles successfully, but during execution it crashes, so I can't use this option.

Answer 1

您的问题与自动链接无关。问题在于您已将 boost::asio（一种具有某种全局状态的仅标头库）导入到两个单独的二进制文件中并将它们链接在一起（可能是一个或多个 dll 和一个 exe）。

通过这样做，您将创建这些对象/函数的多个定义，因此会出现LNK2005错误。这篇文章对此做了一些介绍。您需要按照手册中关于这种情况的说明进行操作，并正确构建。来自文档：

可选单独编译

默认情况下，Boost.Asio 是一个仅包含头文件的库。然而，一些开发人员可能更喜欢使用单独编译的源代码来构建 Boost.Asio。为此，请添加到程序中的 #include <boost/asio/impl/src.hpp> 一个（且仅一个）BOOST_ASIO_SEPARATE_COMPILATION源文件，然后使用项目/编译器设置中定义的内容构建程序。或者，BOOST_ASIO_DYN_LINK可以定义为构建单独编译的 Boost.Asio 作为共享库的一部分。

强调我的。确保您定义了BOOST_ASIO_SEPARATE_COMPILATION所有包含 boost::asio 的关联项目。关于该/FORCE:MULTIPLE选项，假设该标志不存在。正如你所看到的，这是邪恶的。它会将错误扔进垃圾箱，告诉您出现了严重错误。