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visual-studiocmakeclangllvm

Unable to compile llvm pass on Windows using Visual studio

Im learning how to use the llvm toolchain on Windows. I compiled and installed llvm using the following cmake command

cmake -S llvm -B build -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_USE_LINKER=lld -DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_INSTALL_PREFIX="C:\llvm" -Thost=x64

Running the INSTALL project in the solution created in the build folder installed llvm in c:\llvm. To test my llvm installation i created a new Visual Studio project and placed a Directory.build.props file in the project root with the following contents:

<Project>
  <PropertyGroup>
    <LLVMInstallDir>C:\llvm</LLVMInstallDir>
    <LLVMToolsVersion>14.0.0</LLVMToolsVersion>
  </PropertyGroup>
</Project>

I set the project toolchain to LLVM (clang-cl) in project settings and successfully compiled a hello world program.
Now i wanna use llvm for it's intended use and play around with some passes. So i downloaded https://github.com/tsarpaul/llvm-string-obfuscator.
Running cmake -Bbuild -DLLVM_DIR=C:\llvm\lib\cmake\llvm\ generated a Visual Studio solution in .\build.
So far so good i tought. This is similar to the steps required to compile llvm itself.
But running the BUILD_ALL project in the generated solution gave me 105 linker errors.
Errors

I have pasted the entire error output here: https://pastebin.com/TAizbAEi.
I have a feeling the required libraries in C:\llvm\lib are not visible to Visual Studio. But i have no idea how to proceed. Could anyone point me in the right direction on how to use llvm with visual studio correctly?

Solution

  • Solved by adding to the cmake file:

    llvm_map_components_to_libnames(llvm_libs core)
target_link_libraries(LLVMStringObfuscator ${llvm_libs})

    Now the dll build. I still have problems using opt.exe

    PS C:\Users\Administrator\source\repos> C:\llvm\bin\opt.exe -load-pass-plugin=.\11philip22\llvm-string-obfuscator\build\StringObfuscator\Release\LLVMStringObfuscator.dll -passes="string-obfuscator-pass"
C:\llvm\bin\opt.exe: .\11philip22\llvm-string-obfuscator\build\StringObfuscator\Release\LLVMStringObfuscator.dll:1:1: error: expected top-level entity
MZÉ           ╕       @                                   ║ ┤  ═!╕L═!This program cannot be run in DOS mode.

    But that's a new problem for another thread :)