Clangd cannot find standard header

Mon, 15 Jan 2024 00:00:00 +0000

When using clangd (16.0.2) as LSP, it throws the following error:

[pp_file_not_found] Line 1: 'stdlib.h' file not found

But stdlib.h exists, and gcc compilation passed.

TL;DR

Create compilation database file at root of project, content:

-isystem
C:\Users\username\scoop\apps\gcc\current\x86_64-w64-mingw32\include
-target
x86_64-pc-windows-gnu

Where the 2nd line is the path to stdlib.h.

Debug Process

Use --check to run clangd and get error info:

% .\clangd.exe --check=\path\to\file.c

Log:

I[12:18:46.915] clangd version 16.0.2 (https://github.com/llvm/llvm-project 18ddebe1a1a9bde349441631365f0472e9693520)
...
I[12:18:46.924] Loading compilation database...
I[12:18:46.934] Failed to find compilation database for C:\Users\username\path\to\c_file.c
I[12:18:46.935] Generic fallback command is: "C:\\Users\\username\\scoop\\apps\\gcc\\11.2.0\\bin\\clang" "-resource-dir=C:\\Users\\username\\AppData\\Roaming\\nvim-data\\mason\\packages\\clangd\\clangd_16.0.2\\lib\\clang\\16" -- "C:\\Users\\username\\path\\to\\c_file.c"
...
I[12:18:46.970] Testing features at each token (may be slow in large files)
I[12:18:47.006] All checks completed, 2 errors

According to this post, “Generic fallback …” entry means no compilation database. Create an empty compile_flags.txt besides file.c, re-run check command, log:

Clangd on CuSO4_Deposit

Clangd cannot find standard header

TL;DR

Debug Process