Issues with clangd not seeing C++ std libs

[csdarren]

I have been using your plugin for quite awhile now and have just been ignoring the fact that my clangd LSP/Linter config is NOT seeing C++ libs at all... I have not been using clang as a compiler because I simply could never get it to work with ESP32's, so maybe you could help me figure that out but anyways, I can compile everything just fine, but I still get warnings like 'cmath' file not found, or 'string' file not found (#include etc) If you have any ideas or maybe using clang as a compiler will fix all of this, just from what I gather, clang doesn't have much support for ESP32 development.

[dazemc]

I use ccls,

vim.lsp.config("ccls", {
	init_options = {
		compilationDatabaseDirectory = "build",
		index = {
			threads = 2,
			trackDependencies = true,
		},
		clang = {
			excludeArgs = { "-frounding-math" },
		},
	},
})
vim.lsp.enable("ccls")

Really the important part is compliationDatabaseDirectory, otherwise you will need to symlink the compile_commands.json to the project root.

[csdarren]

After quite a few hours today I managed to get ccls working... I am not very good with neovim config but I figured out I was automatically installing clangd each time I would open .cpp because of LazyVim's "Extras" .json file I had... Anyways, this got ccls installed but I still don't have proper include support... I am compiling with GNU still though because I could never get clang to work with ESP-IDF. do you have any tips?

CMake Warning at /opt/esp-idf/components/esp_common/project_include.cmake:14 (message):
Building ESP-IDF with clang is an experimental feature and is not yet
officially supported.
Call Stack (most recent call first):
/opt/esp-idf/tools/cmake/build.cmake:467 (include)
/opt/esp-idf/tools/cmake/build.cmake:718 (__build_process_project_includes)
/opt/esp-idf/tools/cmake/project.cmake:740 (idf_build_process)
CMakeLists.txt:72 (project)

[alanscodelog]

I'm also having issues with this, includes give errors. I'm on nix so I'm using nixpkgs-esp-dev which sets everything up and everything builds fine. Clang is esp-clang. compiler commands file seems to have the correct paths from my research (this is my first time setting this up). Not sure where else to investigate. I'm going to try with another ide to check.

[alanscodelog]

After much pain, I found a solution. Adding "--query-driver=**". I tried pointing the path directly to the xtensa compilers but that didn't work (am not sure why). Here's my flake for reference + lua code to add the arg. It's using devenv as I plan to use it for other things, so ignore all the boilerplate, but the part under mkShell should be easy enough to translate to a regular shell. This also works for vscode as I had also tried it and also ran into issues.

Click to expand

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
    systems.url = "github:nix-systems/default";
    devenv = {
      url = "github:cachix/devenv";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    # does not follow anything
    flake-utils.url = "github:numtide/flake-utils";
    utils = {
      url = "github:alanscodelog/nix-devenv-utils";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    esp-idf = {
      url = "github:mirrexagon/nixpkgs-esp-dev";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  nixConfig = {
    extra-trusted-public-keys = "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw=";
    extra-substituters = "https://devenv.cachix.org";
  };
  outputs =
    { self
    , nixpkgs
    , devenv
    , systems
    , esp-idf
    , utils
    , ...
    } @ inputs:
    let
      forEachSystem = nixpkgs.lib.genAttrs (import systems);
    in
    {
      packages = forEachSystem (system: {
        devenv-up = self.devShells.${system}.default.config.procfileScript;
        devenv-test = self.devShells.${system}.default.config.test;

      });

      devShells = forEachSystem (system:
        let
          pkgs = import nixpkgs {
            inherit system;
            overlays = [
              esp-idf.overlays.default
            ];
          };
        in
        {
          default = devenv.lib.mkShell {
            inherit inputs pkgs;

            modules = [
              ({ pkgs, lib, config, ... }:
                {
                  packages = with pkgs; [
                    esp-idf-full
                    cmake-format
                    gcc-xtensa-lx106-elf-bin
                  ];
                  # vscode esp-idf extension does not work without this, also extension must be installed from vsix from master branch (~1.11)
                  env.LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
                    pkgs.stdenv.cc.cc
                  ];
                  # neovim is configured to parse and append these
                  env.CLANGD_ARGS = "--query-driver=**";
                  enterShell = ''
                  '';
                })
            ];
          };
        });
    };
}

In neovim I do:

local esp32NvimConfig = require("esp32").lsp_config()
local clangd_args = os.getenv("CLANGD_ARGS")
local clangd_args_tbl = {}
if clangd_args then
	for _, arg in ipairs(vim.split(clangd_args, " ")) do
		table.insert(clangd_args_tbl, arg)
	end
end
vim.list_extend(esp32NvimConfig.cmd, clangd_args_tbl)

[Aietes]

I'm not sure if this helps, but proper lsp and linting will only work the Espressif-specific clangd. Did you set it up like this?

idf_tools.py install esp-clang

Create your build directory using clang:

idf.py -B build.clang -D IDF_TOOLCHAIN=clang reconfigure

[csdarren]

I'm not sure if this helps, but proper lsp and linting will only work the Espressif-specific clangd. Did you set it up like this?

idf_tools.py install esp-clang
Create your build directory using clang:

idf.py -B build.clang -D IDF_TOOLCHAIN=clang reconfigure

My problem isn't necessarily with getting espressif's specific clangd installed, its more-so when I try to compile using espressif's clang it doesn't compile at all, and says its unsupported as mentioned above.

So even if I wanted to use the esp specific clangd, i am still compiling with GNU, and esp-clangd doesn't work at all because the compilers are totally different. At least this is how I understand it.

[Aietes]

Are you building with idf.py -B build.clang build and flash with idf.py -B build.clang flash? This should work, and is using clang to compile and flash.

[mikaeleythor]

I am not using this plugin but I came across this issue when debugging the same issue with clangd.
@Aietes suggestion worked for me

idf.py -B build.clang -D IDF_TOOLCHAIN=clang reconfigure

along with setting the following in .clangd inside my project root

CompileFlags:
  CompilationDatabase: build.clang
  Compiler: /nix/store/jwmmz58hhgrv2rh9gb2z8kj5v9bkb4d1-esp-clang-esp-idf-v5.5.1/esp-clang/bin/clang++

where /nix/store/jwmmz58hhgrv2rh9gb2z8kj5v9bkb4d1-esp-clang-esp-idf-v5.5.1/esp-clang/bin/clang++ is the output of which clang++, assuming you have the Espressif fork of clang++

I also have this set in my lsp config:

vim.lsp.enable("clangd")
vim.lsp.config("clangd", {
	cmd = { "clangd", "--enable-config" },
})