Clang toolset support in VS2019

[sammyfreg]

While trying to generate projects with 'Clang' compiler support, I noticed that the built-in LLVM toolset support in VS2019 is not working when using : conf.Options.Add(Sharpmake.Options.Vc.General.PlatformToolset.LLVM);

To fix this, I had to make 2 changes in Sharpmake code, making the result identical to what VisualStudio set on a new project with LLVM toolset :

1. Change the toolset name. Sharpmake currently set 'llvm' in the .vcxprj file but VC2019 expects 'ClangCL' ProjectOptionsGenerator.cs : 1133 Options.Option(Options.Vc.General.PlatformToolset.LLVM, () => { context.Options["PlatformToolset"] = "ClangCL"; })
2. Set the default Clang tool path to '$(LLVMInstallDir)' Util.cs : 1739 return GetRegistryLocalMachineSubKeyValue(registryKeyString, null, @"$(LLVMInstallDir)"); // null to get default

It could also be nice of the documentation mentioned how to activate the LLVM toolset.

[belkiss]

Heya!

Interesting! Sharpmake's support for clang-cl has been mostly tested with vs2017, using the extension from LLVM https://marketplace.visualstudio.com/items?itemName=LLVMExtensions.llvm-toolchain

Is the ClangCL value you mention the one to use for activating the version that you can install with the visual studio installer?

Agreed that the documentation is lacking...

Thanks for the heads-up!

[sammyfreg]

Yes, I don't have any version of Clang installed other than the one you can select when installing VS2019 and making these 2 changes got me past the toolchain associated errors. Now that VS ofter the option to use Clang painlesslly, a lot more people are probably going to try it.

[belkiss]

In that case and in order to keep backward compat we'll need to add another entry in the PlatformToolset enum.

[belkiss]

Support is in the dev branch https://github.com/ubisoft/Sharpmake/commit/d93823ee, will be in the next release.

[sammyfreg]

I have been testing it and still having issues.

Testcase

• With a fresh Window install (sad mishap on my part)
• Installed latest version of: Microsoft Visual Studio Community 2019 - Version 16.7.5 WITH C++ Clang tools for Windows (10.0.0 - x64/x86) component
• Downloaded and compiled Sharpmake Dev 3dd5c9
• Downloaded netImgui
• Edited \Build\netImgui.sharpmake.cs : 134 to conf.Options.Add(Options.Vc.General.PlatformToolset.ClangCL);
• Called GenerateProjects.bat
  • Notice that it doesn't find my Clang toolchain, and picks a default value
  • This default value doesn't exist for me
  • I didn't manually install Clang, just using the one provided in the VS install
  • Message displayed Registry subKey 'SOFTWARE\Wow6432Node\LLVM\LLVM' is not found, fallback to default for value '(Default)': 'C:\Program Files\LLVM'
• I open one of the solution and try to compile the Imgui library (no dependency to other projects).
  • It compiles fine under MS_Debug Target
  • It fails to compile under Clang_Debug Target
  • Error displayed: 1>TRACKER : error TRK0005: Failed to locate: "clang-cl.exe". The system cannot find the file specified. 1>C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\MSBuild\Microsoft\VC\v160\Microsoft.Cpp.ClangCl.Common.targets(378,5): error MSB8057: 'C++ Clang tools for Windows (10.0.0 - x64/x86)' component is not installed in Visual Studio. Open the 'Visual Studio Installer' and install 'C++ Clang tools for Windows (10.0.0 - x64/x86)' under the 'Desktop development with C++' workload. Learn more: https://aka.ms/AA55s5p
• I can fix the compilation error, and make it work by editing
  • Project->Properties : Configuration Properties -> VC++ Directories
  • For every entry, change them to Inherit from parent of project defaults

Executable Dir Before : C:\Program Files\LLVM\bin;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\bin\HostX64\x64;C:\Program Files (x86)\Windows Kits\10\bin\10.0.16299.0\x64;$(PATH) After : $(LLVMInstallDir)\bin;$(ExecutablePath)

Include Dir : C:\Program Files\LLVM\lib\clang\7.0.0\lib\windows;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\lib\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\atlmfc\lib\x64;;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.16299.0\ucrt\x64;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.16299.0\um\x64; After : $(LLVMInstallDir)\x64\lib\clang\10.0.0\include;$(IncludePath)

Library Dir : C:\Program Files\LLVM\lib\clang\7.0.0\lib\windows;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\lib\x64;C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\atlmfc\lib\x64;;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.16299.0\ucrt\x64;C:\Program Files (x86)\Windows Kits\10\Lib\10.0.16299.0\um\x64; After : $(VC_LibraryPath_x64);$(WindowsSDK_LibraryPath_x64)

It feels that for VisualStudio projects, leaving these value blank would be a safer way to go (unless user wants a custom Clang installation).

Replacing C:\Program Files\LLVM with $(LLVMInstallDir) is not sufficient, I end up with compile issues related to findind basic headers 1>..\..\..\Code\ThirdParty\Imgui_17800/imgui.h(58,10): fatal error : 'string.h' file not found. I believe this last point occured with latest version of VS2019, since I also started having the same problem with my previously working modified Sharpmake, since my VS reinstall.

[sammyfreg]

I had to make a small change to the latest branch, for Clang support. In BaseWindowsPlatform.cs I commented out lines 112 - 117 to disable changing the default values.

                if (platformToolset.IsLLVMToolchain())
                {
                    Options.Vc.General.PlatformToolset overridenPlatformToolset = Options.Vc.General.PlatformToolset.Default;
                    if (Options.WithArgOption<Options.Vc.General.PlatformToolset>.Get<Options.Clang.Compiler.LLVMVcPlatformToolset>(conf, ref overridenPlatformToolset))
                        platformToolset = overridenPlatformToolset;

                    devEnv = platformToolset.GetDefaultDevEnvForToolset() ?? devEnv;
                #if 0
                    context.Options["ExecutablePath"] = ClangForWindows.GetWindowsClangExecutablePath() + ";" + devEnv.GetWindowsExecutablePath(conf.Platform);
                    if (Options.GetObject<Options.Vc.LLVM.UseClangCl>(conf) == Options.Vc.LLVM.UseClangCl.Enable)
                    {
                        context.Options["IncludePath"] = ClangForWindows.GetWindowsClangIncludePath() + ";" + devEnv.GetWindowsIncludePath();
                        context.Options["LibraryPath"] = ClangForWindows.GetWindowsClangLibraryPath() + ";" + devEnv.GetWindowsLibraryPath(conf.Platform, Util.IsDotNet(conf) ? conf.Target.GetFragment<DotNetFramework>() : default(DotNetFramework?));
                    }
                #endif
                }

[jonathansty]

I was having a similar issue as @sammyfreg. It seems it's using the wrong paths here, removing the code mentioned also fixes this for me.

[belkiss]

Haven't found the time to test that yet, but would be great if someone could contribute a small sample that enables clang-cl :)

[sammyfreg]

My previous comment has repro for this issue.

You can Download NetImgui and try generating its solution.

[belkiss]

Will do, thanks!

[belkiss]

Heya! Just to let you know that I fixed support for the ClangCL PlatformToolset in the dev branch, by actually removing the whole block of code writing the overrides (c167bc584b3acfbc3a35a187822786f9ceffd87d), since with the improved WinSDK path overrides happening in the vcxproj it's useless.

Some additional fixes were required for everything to behave correctly: e6ae5fed2374ed05a5a66e32cedd1dc466363a28

And I also added a small sample HelloClangCl that shows how to set it up with both MSBuild and FastBuild support in one solution: 5b55a56030119be4b81a776ab6423ca6fb1a5ba8

Hope with all of that we can manage to have it working properly :) Cheers!

[sammyfreg]

I got the latest version and can confirm the Clang support work as is.

Thank you!

[belkiss]

Good to hear! Thanks for the confirmation :)