Clangd intellisense fails, cannot find standard library headers

[noodlecollie]

I've been having issues using clangd with any of my projects on Linux (Ubuntu 22.04) for a long time now. Intellisense fails to recognise pretty much any of my code, to the extent that it's pointless trying to use it.

Today I realised that I had both GCC 11 and 12 installed on my system, and the compile_commands.json was getting a little confused. I've removed GCC 12 and fallen back to 11, but this hasn't made any difference to clangd.

I've run a --check on one of my files (see below) and am getting some errors back that I'm not sure how to resolve. It's particularly suspicious to me that clangd cannot find the filesystem header, since this is part of the standard library in C++17 (which I am passing as a compile parameter).

Logs

Both a verbose and non-verbose log are attached, for a manual --check run on one of my source files that fails.

clangd.log
clangd_verbose.log

System information
clangd version 19.1.2 (https://github.com/llvm/llvm-project 7ba7d8e2f7b6445b60679da826210cdde29eaf8b)
Features: linux+grpc
Platform: x86_64-unknown-linux-gnu

clangd extension version: 0.2.0 (Used in VS Codium, rather than VS Code)

Operating system: Ubuntu 22.04.5 LTS

[HighCommander4]

Your logs are suggesting that clangd is still trying to find gcc 12 standard library headers.

Based on previous investigations of similar issues (see this comment in particular), the most common solution is to install g++-12, but see also the other options listed there (using --query-driver is what I would classify as the most accurate one, as you're explicitly telling clangd which compiler's system headers to search for).

[noodlecollie]

Ah, that linked page was super useful, thanks. I suspect Ubuntu's build-essential package included gcc and g++ 11, but me (or the system) updating "GCC" as a toolchain only pulled in the gcc executable and not g++.

Seems this has solved things - FYI for anyone else who happens upon this, I followed https://askubuntu.com/questions/26498/how-to-choose-the-default-gcc-and-g-version to properly install GCC/G++ 11 and 12 alongside each other.