Integrate LLVM Clang 4.x.x / 5.x.x / 6.x.x into Visual Studio 2017

Question

The official LLVM 4.0 build for Windows integrates with Visual Studio up to Visual Studio 2015. Unfortunately it still doesn\'t support Visual Studio 2017.

When you

Answer 1

LLVM/Clang now has an updated patch that allows you to use it with VS2017. But they still don't directly support VS2017. I asked on the LLVM developer mailing list for them to update their support for VS2017, so hopefully they'll do it. If they listen to what I said.

Answer 2

Check out January 09, 2018 http://planet.clang.org/

Look at the "Try it out!" section:

If you're already using clang-cl and lld-link on Windows today, you can try this out. There are two flags needed to enable this, one for the compiler and one for the linker: To enable the emission of a .debug$H section by the compiler, you will need to pass the undocumented -mllvm -emit-codeview-ghash-section flag to clang-cl (this flag should go away in the future, once this is considered stable and good enough to be turned on by default). To tell lld-link to use this information, you will need to pass the /DEBUG:GHASH to lld.

You just need to pass the -mllvm -emit-codeview-ghash-section flags in either your c++ projects "Command Line:Additional Options" area, or place them directly in the "toolset.props" file that you created in C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\VC\VCTargets\Platforms\Win32\PlatformToolsets\LLVM-vs2017 or C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\VC\VCTargets\Platforms\x64\PlatformToolsets\LLVM-vs2017.

The key is that in adding those cli options you're telling clang to emit debug information that the lld (aka lld-link) will understand and use to produce fully populated PDB files. Not the limited ones it made prior to the Jan 09, 2018 drops of LLVM 7.0.

toolset.targets: (any version)

<Project ToolsVersion="14.1" 
xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(VCTargetsPath)\Microsoft.CppCommon.targets" />
</Project>

toolset.props: (Win32 version)

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">  
  <Import Project="$(VCTargetsPath)\Platforms\$(Platform)\PlatformToolsets\v141\Microsoft.Cpp.$(Platform).v141.props" Condition="Exists('$(VCTargetsPath)\Platforms\$(Platform)\PlatformToolsets\v141\Microsoft.Cpp.$(Platform).v141.props')"/>
  <Import Project="$(VCTargetsPath)\Platforms\$(Platform)\PlatformToolsets\v141\Toolset.props" Condition="Exists('$(VCTargetsPath)\Platforms\$(Platform)\PlatformToolsets\v141\Toolset.props')"/>

  <PropertyGroup>
    <LLVMInstallDir>$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\LLVM\LLVM)</LLVMInstallDir>
    <LLVMInstallDir Condition="'$(LLVMInstallDir)' == ''">$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\LLVM\LLVM)</LLVMInstallDir>
    <ExecutablePath>$(LLVMInstallDir)\msbuild-bin;$(ExecutablePath)</ExecutablePath>
    <LibraryPath>$(LLVMInstallDir)\lib\clang\7.0\lib\windows;$(LibraryPath)</LibraryPath>
  </PropertyGroup>

  <ItemDefinitionGroup>
    <ClCompile>
      <!-- remove the implicit vcxxx.pdb path to avoid rebuilds every time as clang-cl only supports /Z7 -->
      <ProgramDataBaseFileName></ProgramDataBaseFileName>
      <!-- Set the value of _MSC_VER to claim for compatibility -->
      <AdditionalOptions>-m32 -fmsc-version=1913 %(AdditionalOptions)</AdditionalOptions>
    </ClCompile>
  </ItemDefinitionGroup>
</Project>

For x64, change -m32 to -m64

p.p.s., I have also enabled Microsofts ARM and ARM64 compilers for building native Windows-10-ARM apps (not UWP modern-com-junk). But, as yet, I have not done enough digging through the clang sources to properly configure something similar for ARM to what -m32 and -m64 do for Intel code-gen.

See these articles:

• http://pete.akeo.ie/2017/05/compiling-desktop-arm-applications-with.html

• https://www.theverge.com/2017/12/5/16737288/microsoft-windows-10-qualcomm-arm-laptops-launch

• https://wiki.winehq.org/ARM

Answer 3

It requires some msbuild targets that only ship with the C++ v140 toolset, and VS 2017 only installs the v141 toolset by default. If you open the VS 2017 installer, find the checkbox for the v140 toolset and install that then the right C++ msbuild targets will be available and the thing will work.

Answer 4

Finally, I found a brilliant GitHub repo with the required MSBuild platform toolsets which integrates LLVM clang 5.0.0 into Visual Studio 2017. After following the instructions of the README file, you will have two new platform toolsets LLVM-vs2017 and LLVM-vs2017_xp. Problem solved.

Update

I made a fork which is updated for LLVM 6.0.0 and provides better integration by providing include and library paths of LLVM/clang.

Thanks to Royi, who realized that the original .prop files are explicitly tailored for LLVM 5.0 and it misses adding the proper lib ( $(LLVMInstallDir)\lib) and include ($(LLVMInstallDir)\lib\clang\6.0.0\include) folders.

Answer 5

The LLVM project now explicitly supports Visual Studio 2017 via https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain

Answer 6

I have figured out how to integrate LLVM Clang 7.0 with Visual Studio 2017 update 15.5.6. v1913 with full support for PDB based debugging using the latest LLVM builds.

i.e., lld-link /DEBUG:GHASH; clang-cl -mllvm -emit-codeview-ghash-section flag to clang-cl.

It is a three step process.

1. Install latest llvm
2. Update the toolset.props, toolset.targets in VS to support latest clang
3. Select the new toolset to use for building your C/C++ or other lang project

As of Visual Studio 2017 update 15.4.5 the Microsoft "experimental" Clang C2 no longer works. Thus, the above fixes are necessary to use clang to compile code that has full PDB (not just CodeView /Z7 limited) debuggability. This also now becomes a more complete suite for portability testing cross-platform builds since you can build and PDB debug for windows using all LLVM components from the clang compiler front end to the LLVM codegen backend and LLVM linker.

Cheers, David