[llvm-dev] Building A Project Against LLVM

[Rarrum via llvm-dev]

I've managed to get 10.0.0 working now.. there were a couple things I had
to adjust.

The Kaleidoscope example had me doing this before creating the object file:
llvm::InitializeAllTargetInfos();
llvm::InitializeAllTargets();
llvm::InitializeAllTargetMCs();
llvm::InitializeAllAsmParsers();
llvm::InitializeAllAsmPrinters();

It turns out I can get away with just this, since I'm not (yet) worried
about targeting other machines:
llvm::InitializeNativeTarget();
llvm::InitializeNativeTargetAsmPrinter();

Since "all" doesn't work anymore for some reason, I've managed to (through
trial and error, guessing at different names shown from llvm-config
--components) end up with this set of libnames:
llvm_map_components_to_libnames(llvm_libs core executionengine support
nativecodegen)

That left me with 2 link errors referring to llvm::raw_ostream and
llvm::raw_pwrite_stream.  After much more digging through similar
complaints on the internet.. the last fix turned out to be adding this to
CMakeLists.txt:
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")

I am a little worried that the rtti flag may come back and bite me later
when I get around to building this on windows again (since I do use
exceptions), but that's a problem for another day.


One last question.. is there a good way to know which libnames I need,
based on which #includes I pull in or which classes I'm using?  I didn't
see anything obvious in the doxygen documentation.


On Fri, May 15, 2020 at 8:57 PM Rarrum <rarrum at gmail.com> wrote:

> I'd rather avoid updating my OS at the moment or setting up a VM.  But the
> cmake comments were a hint.. I suspect something is going wrong in there
> preventing it from adding the actual library files to the linker
> commandline.
>
> I added this to my CMakeLists.txt:
> set(CMAKE_VERBOSE_MAKEFILE on)
>
> Which shows no LLVM libs at all being passed in:
>
> [  8%] Linking CXX executable ../bin/CBreakCompiler
> /usr/bin/c++     CMakeFiles/CBreakCompiler.dir/src/main.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/Parser.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/SourceTokenizer.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/IRCompiler.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/JIT.cpp.o  -o ../bin/CBreakCompiler
>
> If I change this:
> llvm_map_components_to_libnames(llvm_libs all)
> to:
> llvm_map_components_to_libnames(llvm_libs core)
>
> Then I start to see libraries being added:
> [  8%] Linking CXX executable ../bin/CBreakCompiler
> /usr/bin/c++     CMakeFiles/CBreakCompiler.dir/src/main.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/Parser.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/SourceTokenizer.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/IRCompiler.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o
> CMakeFiles/CBreakCompiler.dir/src/JIT.cpp.o  -o ../bin/CBreakCompiler
> /usr/local/lib/libLLVMCore.a /usr/local/lib/libLLVMBinaryFormat.a
> /usr/local/lib/libLLVMRemarks.a /usr/local/lib/libLLVMBitstreamReader.a
> /usr/local/lib/libLLVMSupport.a -lrt -ldl -ltinfo -lpthread -lm
> /usr/local/lib/libLLVMDemangle.a
>
> Perhaps I can figure out which ones I need and manually specify them all,
> rather than using "all".
>
> On Fri, May 15, 2020 at 8:17 PM Mehdi AMINI <joker.eph at gmail.com> wrote:
>
>>
>>
>> On Fri, May 15, 2020 at 6:53 PM Neil Nelson via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Rarrum,
>>>
>>> Kubuntu 20.04 LTS is available. You may be able to upgrade to 19.10, and
>>> then to 20.04 without reinstalling. It can be done on Xubuntu. A direct
>>> upgrade to 20.04 should become available. LLVM 10 then installs from the
>>> distribution packages. I put all this on a VM using KVM/QEMU to keep it
>>> isolated from my primary desktop environment. Building a 20.04 VM after
>>> upgrading to 20.04 appears to give a faster VM. Use llvm's linker lld.
>>>
>>> The cmake version for 20.04 is 3.16.3 which should help with llvm's
>>> recommended version.
>>>
>>
>> Do you believe the error listed have to do with the CMake version?
>>
>>
>>
>>
>>> Neil
>>> On 5/15/20 12:05 AM, Rarrum via llvm-dev wrote:
>>>
>>> I decided to start playing around with building my own programming
>>> language recently, and to use LLVM to handle the assembly-level details.
>>> I'm on Kubuntu 18.04, and I started out using LLVM 6.0 from Kubuntu's
>>> packages.  I put together code for dealing with my language, then went over
>>> the Kaleidoscope tutorials (which have been extremely helpful btw!).  I was
>>> able to successfully get my own compiler to generate IR using LLVM, use
>>> PassManager to write that to a native .o file, use gcc to link that, and
>>> execute a tiny program written in my own language.
>>>
>>> I also decided it was a good time to learn CMake, so I set up my project
>>> using that.  The CMakeLists.txt file I'm using is essentially just taken
>>> from: https://llvm.org/docs/CMake.html#embedding-llvm-in-your-project -
>>> though originally it would not link.  From scouring the internet I made 2
>>> changes to get that working: replaced "support core irreader" with "all",
>>> and replaced "${llvm_libs}" with just "LLVM".
>>>
>>> However as I was starting to play with setting up JIT, I hit more
>>> differences between the version of LLVM in Kubuntu and the version the
>>> examples and documentation were written against.  So I decided to try to
>>> update to a newer version of LLVM.. and this is where I've been stuck for
>>> several days now.  Here are the steps I've taken:
>>>
>>> * Uninstalled any llvm packages I could find from Kubuntu's package
>>> manager.
>>> * Followed the getting started guide:
>>> https://llvm.org/docs/GettingStarted.html - I git cloned LLVM, checked
>>> out the 10.0.0 tag, ran cmake as instructed, with the Release type.  When
>>> that completed successfully I ran sudo ninja install.
>>> * I then went back to my project and adjusted a couple places to
>>> successfully compile against the new version.
>>> * At this point I put "${llvm_libs}" in the CMakeLists.txt file back to
>>> match the example.  However I was getting a massive wall of link errors.
>>> * I assumed I must have built LLVM incorrectly somehow, so in an effort
>>> to undo that install, I deleted everything I could find under /usr/local
>>> that had LLVM in its name, downloaded the 10.0 release from
>>> https://releases.llvm.org/download.html for ubuntu 18.04, and extracted
>>> that all to /usr/local.
>>> * I can still successfully compile, but not link.
>>>
>>> At this point I'm not sure what to try next.  Is there additional
>>> documentation somewhere for how to "install" a current release of LLVM
>>> correctly?
>>>
>>>
>>> For reference here's my final CMakeLists.txt file:
>>>
>>> cmake_minimum_required(VERSION 3.10)
>>>
>>> project(CBreakCompiler)
>>>
>>> set(CMAKE_CXX_STANDARD 17)
>>> set(CMAKE_CXX_STANDARD_REQUIRED True)
>>> add_compile_options(-Wall)
>>>
>>> find_package(LLVM 10.0.0 REQUIRED CONFIG)
>>>
>>> message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
>>> message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
>>>
>>> include_directories(${LLVM_INCLUDE_DIRS})
>>> add_definitions(${LLVM_DEFINITIONS})
>>>
>>> add_executable(CBreakCompiler
>>>     src/main.cpp
>>>     src/Parser.cpp
>>>     src/SourceTokenizer.cpp
>>>     src/IRCompiler.cpp
>>>     src/CompiledOutput.cpp)
>>>
>>> llvm_map_components_to_libnames(llvm_libs all)
>>> target_link_libraries(CBreakCompiler ${llvm_libs})
>>>
>>>
>>> And a snippet from the cmake output corresponding to those message lines:
>>>
>>> -- Found LLVM 10.0.0
>>> -- Using LLVMConfig.cmake in: /usr/local/lib/cmake/llvm
>>>
>>>
>>> There are dozens of link errors.. the first few and last few are:
>>>
>>> CMakeFiles/CBreakCompiler.dir/src/main.cpp.o:(.data.rel+0x0): undefined
>>> reference to `llvm::DisableABIBreakingChecks'
>>> CMakeFiles/CBreakCompiler.dir/src/main.cpp.o: In function
>>> `std::default_delete<llvm::LLVMContext>::operator()(llvm::LLVMContext*)
>>> const':
>>> main.cpp:(.text._ZNKSt14default_deleteIN4llvm11LLVMContextEEclEPS1_[_ZNKSt14default_deleteIN4llvm11LLVMContextEEclEPS1_]+0x1e):
>>> undefined reference to `llvm::LLVMContext::~LLVMContext()'
>>> ...
>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0xe0):
>>> undefined reference to `llvm::raw_ostream::anchor()'
>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0xf8):
>>> undefined reference to `typeinfo for llvm::raw_pwrite_stream'
>>> CMakeFiles/CBreakCompiler.dir/src/CompiledOutput.cpp.o:(.data.rel.ro+0x110):
>>> undefined reference to `typeinfo for llvm::raw_ostream'
>>>
>>>
>> Seems like `llvm_map_components_to_libnames` wasn't populated well?
>> I'd start by printing `${llvm_libs}` in your CMake to check the output
>> of llvm_map_components_to_libnames, I don't know how the "all" works for
>> external builds? You may have to list the components you need more
>> explicitly instead?
>>
>> --
>> Mehdi
>>
>>
>>
>>
>>
>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing listllvm-dev at lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
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>>>
>>
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