[llvm-dev] Using LLD to link against third-party libraries? How?

Osman Zakir via llvm-dev llvm-dev at lists.llvm.org
Wed Dec 12 08:16:26 PST 2018 

I need them so I can build stuff using clang or clang-cl with its C++ standard libraries.  To make sure that lld-link won't give errors about missing symbols from any standard libraries.

By the way, you wouldn't happen to know how to use link.exe, would you?  I might need some help on that to understand how to use lld-link.exe.
________________________________
From: Zachary Turner <zturner at google.com>
Sent: Wednesday, December 12, 2018 9:02 PM
To: Osman Zakir; llvm-dev
Subject: Re: [llvm-dev] Using LLD to link against third-party libraries? How?

Do you have a specific reason for enabling libcxx and libcxxabi?  Because I would strongly suggest disabling them otherwise

On Wed, Dec 12, 2018 at 7:47 AM Osman Zakir <osmanzakir90 at hotmail.com<mailto:osmanzakir90 at hotmail.com>> wrote:
I was asking about zlib because CMake couldn't find zlib.  There was no error in the configuration, but knowing how to set the path to zlib would still be nice.

I enabled clang, lld, lldb, libcxx and libcxxabi when configuring the build with CMake.  What projects should I build aside from ALL_BUILD.vcxproj and INSTALL.vcxproj to make sure I get the libcxx and libcxxabi projects built as well, along with lld, lldb and clang?

I didn't know about the bootstrapping Clang with itself bit, so I didn't do that.
________________________________
From: Zachary Turner <zturner at google.com<mailto:zturner at google.com>>
Sent: Wednesday, December 12, 2018 8:40 PM
To: Osman Zakir
Cc: llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>

Subject: Re: [llvm-dev] Using LLD to link against third-party libraries? How?

If you want to bootstrap clang and lld using itself, then you should pass -DCMAKE_C_COMPILER=path/to/clang-cl.exe -DCMAKE_CXX_COMPILER=path/to/clang-cl.exe -DCMAKE_LINKER=path/to/lld-link.exe.

Note the clang-cl.exe.  ***Not*** clang.exe or clang++.exe.

On Wed, Dec 12, 2018 at 7:37 AM Zachary Turner <zturner at google.com<mailto:zturner at google.com>> wrote:
You shouldn't need zlib to build.  I think we discussed in a previous thread that the only components you should need to complete a build are Microsoft Visual Studio, git, and CMake.

On Wed, Dec 12, 2018 at 7:14 AM Osman Zakir via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
How can I tell CMake during the configuration step where to find my zlib installation?
________________________________
From: blubee blubeeme <gurenchan at gmail.com<mailto:gurenchan at gmail.com>>
Sent: Wednesday, December 12, 2018 7:31 PM

To: Osman Zakir
Cc: llvm-dev
Subject: Re: [llvm-dev] Using LLD to link against third-party libraries? How?
I would agree with the next email from
Brian Cain

If you do not have specific reason to want to use llvm lld try to use your system provided c++ linker.

Bootstrapping the llvm c++ c++abi can be troublesome on Unix like platforms and I have no experience doing anything like that on windows.

If you already have a c++ toochain and still want to attempt this then you'll need to svn checkout or git clone a version of the llvm toolchain and build it with your native toolchain then switch to using clang and lld.

if you do not have a native c++ toolchain; let's cross that bridge only if you need to.

A complete LLVM toolchain includes
llvm
clang
clang-extra-tools
lld
lldb
polly
compiler-rt
openmp
libcxx
libcxx-abi
testsuite
There's "Getting Started Quickly (A Summary" : https://llvm.org/docs/GettingStarted.html

With steps to build a complete toolchain. Compilation could take a long time.

It would be simpler to use your native c++ and linker unless they do not provide c++17 in which case the above link can get you started.

Best

On Wed, Dec 12, 2018 at 8:57 PM Osman Zakir <osmanzakir90 at hotmail.com<mailto:osmanzakir90 at hotmail.com>> wrote:
So how do I get it to build libcxx and libcxxabi?  I got it from the mono repo and enabled lld, clang, libcxx and libcxxabi.  But I built the two main CMake targets only--all_build and install.  What else do I have to do?  Please let me know.
________________________________
From: Zachary Turner <zturner at google.com<mailto:zturner at google.com>>
Sent: Wednesday, December 12, 2018 11:10 AM
To: blubee blubeeme
Cc: Osman Zakir; David Greene; llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] Using LLD to link against third-party libraries? How?

I see you’re using lld-link, so we’re talking about Windows here.

Have you gotten it working with the Microsoft linker? Because if so, just replace link.exe with lld-link.exe and it will work.

Btw, it’s a bit odd to use clang++ on Windows. The recommended workflow is to use clang-cl. It’s possible to use clang++, but you’re just setting yourself up for more difficulty
On Tue, Dec 11, 2018 at 7:23 PM blubee blubeeme via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
I couldn't get it to build libcxx...
You need c++ and c++abi to compile c++ code.


On Wed, Dec 12, 2018, 07:01 Osman Zakir via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
LLVM on a Developer Command Prompt.  The ones I want to fix first are the ones from Boost and Jinja2Cpp.  I saw some from those as well.

If there any standard library ones missing, could it be because I couldn't get it to build libcxx?  I did try to include that, but it seems to be missing.  What should I do?
________________________________
From: David Greene <dag at cray.com<mailto:dag at cray.com>>
Sent: Wednesday, December 12, 2018 3:30 AM
To: Osman Zakir
Cc: blubee blubeeme; llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>

Subject: Re: [llvm-dev] Using LLD to link against third-party libraries? How?

Are you linking with a C++ compiler?  A lot of those missing symbols
look like they come from the C++ standard library.

                          -David

Osman Zakir via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> writes:

> @blubee blubeeme So what do you think? Got any ideas?
> ----------------------------------------------------------------------
> From: Osman Zakir <osmanzakir90 at hotmail.com<mailto:osmanzakir90 at hotmail.com>>
> Sent: Wednesday, December 12, 2018 1:43 AM
> To: llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
> Subject: Re: [llvm-dev] Using LLD to link against third-party
> libraries? How?
> In my code here https://github.com/DragonOsman/currency_converter , I
> used C++17 and managed to get it to work (though I'm only using
> std::map::insert_or_assign() from C++17). And I'm using Windows, so I
> shouldn't use LDFLAGS or CXXFLAGS as environment variables. I'll use
> them directly on the compiler command line instead. The libraries I
> need to link against are
> C:/boost_1_68_0/stage/lib/libboost_system-vc141-mt-x64-1_68.lib and
> C:/Jinja2Cpp/install_x64/lib/static/jinja2cpp.lib.
>
> I tried to build it with this flag:
> "
> clang++ -std=c++17 -Wall -pedantic -
> D_SILENCE_CXX17_ADAPTOR_TYPEDEFS_DEPRECATION_WARNING -
> Dvariant_CONFIG_SELECT_VARIANT=variant_VARIANT_NONSTD -
> D_SILENCE_CXX17_ALLOCATOR_VOID_DEPRECATION_WARNING -
> D_CRT_SECURE_NO_WARNINGS -D_WINSOCK_DEPRECATED_NO_WARNINGS -D_WIN32 -
> D_WIN32_WINDOWS -D_NDEBUG -fexceptions -
> IC:/Jinja2Cpp/install_x64/include -IC:/json/single_include -
> IC:/boost_1_68_0 -
> LC:/boost_1_68_0/stage/lib/libboost_system-vc141-mt-x64-1_68.lib -
> LC:/Jinja2Cpp/install_x64/lib/static/jinja2cpp.lib
> currency_converter.cpp -o currency_converter.exe
> "
> And I got these warnings and errors from LLD:
>
> "
> lld-link: warning:
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o: locally
> defined symbol imported: __std_terminate (defined in libvcruntime.lib
> (ehhelpers.obj)) [LNK4217]
> lld-link: error: undefined symbol: "public: __cdecl
> jinja2::Template::Template(class jinja2::TemplateEnv *)"
> (??0Template at jinja2@@QEAA at PEAVTemplateEnv@1@@Z)​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("void _
> _cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> boost::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)"
> (??$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $allocator at D@std@@AEAUsend_lambda at server_session@@@@YAXV?$basic_string_
> view at DU?$char_traits at D@std@@@boost@@$$QEAU?$message@$00U?$basic_string_
> body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?$basic_
> fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_session@@PEBD3 at Z)
> )​
> ​
> lld-link: error: undefined symbol: "public: class
> nonstd::expected_lite::expected<void, class
> jinja2::ErrorInfoTpl<char>> __cdecl jinja2::Template::LoadFromFile
> (class std::basic_string<char, struct std::char_traits<char>, class
> std::allocator<char>> const &)"
> (?LoadFromFile at Template@jinja2@@QEAA?AV?$expected at XV?$ErrorInfoTpl at D@jinja2@@@expected_
> lite at nonstd@@AEBV?$basic_string at DU?$char_traits at D@std@@V?$allocator at D@2@@std@@@Z)
> ​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("void _
> _cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> boost::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)"
> (??$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $allocator at D@std@@AEAUsend_lambda at server_session@@@@YAXV?$basic_string_
> view at DU?$char_traits at D@std@@@boost@@$$QEAU?$message@$00U?$basic_string_
> body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?$basic_
> fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_session@@PEBD3 at Z)
> )​
> ​
> lld-link: error: undefined symbol: "public: class
> std::basic_string<char, struct std::char_traits<char>, class
> std::allocator<char>> __cdecl jinja2::Template::RenderAsString(class
> std::unordered_map<class std::basic_string<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> jinja2::Value, struct std::hash<class std::basic_string<char, struct
> std::char_traits<char>, class std::allocator<char>>>, struct
> std::equal_to<class std::basic_string<char, struct
> std::char_traits<char>, class std::allocator<char>>>, class
> std::allocator<struct std::pair<class std::basic_string<char, struct
> std::char_traits<char>, class std::allocator<char>> const, class
> jinja2::Value>>> const &)"
> (?RenderAsString at Template@jinja2@@QEAA?AV?$basic_string at DU?$char_traits at D@std@@V?
> $allocator at D@2@@std@@AEBV?$unordered_map at V?$basic_string at DU?$char_traits at D@std@@V?
> $allocator at D@2@@std@@VValue at jinja2@@U?$hash at V?$basic_string at DU?$char_traits at D@std@@V?
> $allocator at D@2@@std@@@2 at U?$equal_to at V?$basic_string at DU?$char_traits at D@std@@V?
> $allocator at D@2@@std@@@2 at V?$allocator at U?$pair@$$CBV?$basic_string at DU?$char_
> traits at D@std@@V?$allocator at D@2@@std@@VValue at jinja2@@@std@@@2@@4@@Z)​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("void _
> _cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> boost::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)"
> (??$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $allocator at D@std@@AEAUsend_lambda at server_session@@@@YAXV?$basic_string_
> view at DU?$char_traits at D@std@@@boost@@$$QEAU?$message@$00U?$basic_string_
> body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?$basic_
> fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_session@@PEBD3 at Z)
> )​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("void _
> _cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> boost::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)"
> (??$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $allocator at D@std@@AEAUsend_lambda at server_session@@@@YAXV?$basic_string_
> view at DU?$char_traits at D@std@@@boost@@$$QEAU?$message@$00U?$basic_string_
> body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?$basic_
> fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_session@@PEBD3 at Z)
> )​
> ​
> lld-link: error: undefined symbol: "public: __cdecl
> jinja2::Template::~Template(void)" (??1Template at jinja2@@QEAA at XZ)​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("void _
> _cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> boost::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)"
> (??$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $allocator at D@std@@AEAUsend_lambda at server_session@@@@YAXV?$basic_string_
> view at DU?$char_traits at D@std@@@boost@@$$QEAU?$message@$00U?$basic_string_
> body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?$basic_
> fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_session@@PEBD3 at Z)
> )​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("int
> `void __cdecl handle_request<struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> std::allocator<char>, struct server_session::send_lambda &>(class
> boost::basic_string_view<char, struct std::char_traits<char>>, struct
> basic_string_view<char, struct
> std::char_traits<char>>::beast::http::message<1, struct
> boost::beast::http::basic_string_body<char, struct
> std::char_traits<char>, class std::allocator<char>>, class
> boost::beast::http::basic_fields<class std::allocator<char>>> &&,
> struct server_session::send_lambda &, char const *, char const *)'::
> `1'::dtor$114"
> (?dtor$114@?0???$handle_request at U?$basic_string_body at DU?$char_traits at D@std@@V?
> $allocator at D@2@@http at beast@boost@@V?$allocator at D@std@@AEAUsend_lambda at server_
> session@@@@YAXV?$basic_string_view at DU?$char_traits at D@std@@@boost@@$$QEAU?
> $message@$00U?$basic_string_body at DU?$char_traits at D@std@@V?$allocator at D@2@@http at beast@boost@@V?
> $basic_fields at V?$allocator at D@std@@@234@@http at beast@1 at AEAUsend_lambda@server_
> session@@PEBD3 at Z@4HA))​
> ​
> lld-link: warning:
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o: locally
> defined symbol imported: _CxxThrowException (defined in
> libvcruntime.lib(throw.obj)) [LNK4217]​
> lld-link: error: undefined symbol: "class
> boost::system::error_category const & __cdecl
> boost::system::detail::system_category_ncx(void)"
> (?system_category_ncx at detail@system at boost@@YAAEBVerror_category at 23@XZ)​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("class
> boost::system::error_category const & __cdecl
> boost::system::system_category(void)"
> (?system_category at system@boost@@YAAEBVerror_category at 12@XZ))​
> ​
> lld-link: warning:
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o: locally
> defined symbol imported: __RTDynamicCast (defined in libvcruntime.lib
> (rtti.obj)) [LNK4217]​
> lld-link: error: undefined symbol: "class
> boost::system::error_category const & __cdecl
> boost::system::detail::generic_category_ncx(void)"
> (?generic_category_ncx at detail@system at boost@@YAAEBVerror_category at 23@XZ)
> ​
>>>> referenced by
> C:\Users\Osman\AppData\Local\Temp\currency_converter-264ae1.o:("class
> boost::system::error_category const & __cdecl
> boost::system::generic_category(void)"
> (?generic_category at system@boost@@YAAEBVerror_category at 12@XZ))​
> clang++: error: linker command failed with exit code 1 (use -v to see
> invocation)
> "
>
>
>  * GitHub - DragonOsman/currency_converter: Application for Computer
>    Science course
>    Google Maps + Currency Converter Web Application. Application for
>    Computer Science course. This is a currency converter web
>    application with the frontend and a backend.
>    github.com<http://github.com>
>
> *
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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