Can't clangd in cmake (already enabled export compile command) work out of the box?

[K1ngst0m]

[UPDATE]: Thanks for @HighCommander4

When I running, I got the message:
zsh: no such file or directory: /usr/lib/llvm/14/bin/g++
, I notice this option exists but I didn't spec manually:--driver-mode=g++
So I guess this is triggered by my compile_command.json, so I add these

set(CMAKE_C_COMPILER clang)
set(CMAKE_CXX_COMPILER clang++) 

, I regenerate compile_command.json, and the errors are just gone!

[ORIGIN]

In my emacs, I use lsp-emacs + clangd, there are so many clangd error outputs but it can compile success, there's also happened in other projects. And when I use clion with clangd these errors are just gone and the syntax check outputs are the same as compiler compilation output.

These are my operations when I get starting with a project:
cmake -B build -DCMAKE_EXPORT_COMPILE_COMMAND=YES -DCMAKE_BUILD_TYPE=Debug && ln -s build/compile_command.json ..

Are there any operations and configurations I missed?

[clion] clangd configuration	[emacs] lsp error outputs with clangd backend

Here are my clangd-related configurations, the error still produces whether these configurations exist or not.

clangd arguments	clangd/config.yaml

Here's my collected info following the troubleshooting guide

[HighCommander4]

As mentioned on Discord, we need clangd logs to investigate what is going wrong. Clangd writes its logs to stderr and clients should expose a way to access that.

I'm not familiar with Emacs, but assuming you're using lsp-mode, some searching suggests (based on e.g. this FAQ entry) that the clangd logs are stored in a buffer called *clangd::stderr*.

[K1ngst0m]

here's my testing project

[HighCommander4]

Thanks! The relevant part of the log is:

I[10:44:51.570] ASTWorker building file /home/npchitman/workspace/Aphrodite/Aphrodite-Runtime/src/Aphrodite/Renderer/Buffer.cpp version 0 with command
[/home/npchitman/workspace/Aphrodite/build/debug/Aphrodite-Runtime]
/usr/lib/llvm/14/bin/g++ --driver-mode=g++ -DAPH_DEBUG -DAPH_ENABLE_ASSERTS -DAphrodite_Runtime_EXPORTS -DB2_SHARED -DFMT_SHARED -DSPDLOG_COMPILED_LIB -DSPDLOG_SHARED_LIB -I/home/npchitman/workspace/Aphrodite/Aphrodite-Runtime/include -I/home/npchitman/workspace/Aphrodite/Aphrodite-Runtime/src -I/home/npchitman/workspace/Aphrodite/3rdparty/stb -I/home/npchitman/workspace/Aphrodite/3rdparty/glad/include -I/home/npchitman/workspace/Aphrodite/3rdparty/entt/include -I/home/npchitman/workspace/Aphrodite/3rdparty/spirv-cross -I/home/npchitman/workspace/Aphrodite/3rdparty/imgui -I/home/npchitman/workspace/Aphrodite/3rdparty/glm -I/home/npchitman/workspace/Aphrodite/3rdparty/yaml-cpp -I/home/npchitman/workspace/Aphrodite/3rdparty/ImGuizmo -I/home/npchitman/workspace/Aphrodite/3rdparty/glfw/include -I/home/npchitman/workspace/Aphrodite/3rdparty/imgui/. -I/home/npchitman/workspace/Aphrodite/3rdparty/imgui/backends -I/home/npchitman/workspace/Aphrodite/3rdparty/box2d/src/../include -I/home/npchitman/workspace/Aphrodite/3rdparty/spdlog/include -I/home/npchitman/workspace/Aphrodite/3rdparty/yaml-cpp/include -g -fPIC -std=gnu++17 -Winvalid-pch -include /home/npchitman/workspace/Aphrodite/build/debug/Aphrodite-Runtime/CMakeFiles/Aphrodite-Runtime.dir/cmake_pch.hxx -o CMakeFiles/Aphrodite-Runtime.dir/src/Aphrodite/Renderer/Buffer.cpp.o -c -xc++ -std=c++17 -Wall -resource-dir=/usr/lib/llvm/14/bin/../../../../lib/clang/14.0.1 -- /home/npchitman/workspace/Aphrodite/Aphrodite-Runtime/src/Aphrodite/Renderer/Buffer.cpp

Could you try the following please:

• In a terminal, cd into /home/npchitman/workspace/Aphrodite/build/debug/Aphrodite-Runtime
• Run the full command from the quoted log (starting with /usr/lib/llvm/14/bin/g++)

Do you get any errors?

[K1ngst0m]

when I running, I got the message:
zsh: no such file or directory: /usr/lib/llvm/14/bin/g++
, I notice this option exists but I didn't spec manually:--driver-mode=g++
So I guess this is triggered by my compile_command.json, so I add these

set(CMAKE_C_COMPILER clang)
set(CMAKE_CXX_COMPILER clang++) 

, and regenerate compile_command.json, and the errors are just gone!

---

Thanks for your help, and I wonder how can I use clangd in the projects which are GCC only (such as my company's project)?

[HighCommander4]

I wonder how can I use clangd in the projects which are GCC only (such as my company's project)?

I guess that's going to depend on the reason why the project is GCC only.

If the project's code uses some language extension which only GCC supports and not clang (note, this should be rare, clang makes an effort to support most GCC extensions), then you will not be able to use it (or at least, you will have to put up with clangd giving errors in code that uses those extensions).

But if it's more just "no one bothered to add clang support to the project's build system", then you can probably get clangd to parse it, perhaps with some compiler flag overrides in config.yaml (with CompileFlags: Add: and Remove:). I'm happy to try and help with specific examples.

[K1ngst0m]

Thank you very much. I guess I will try to persuade them for adding clang to the building system.😊