Why does clangd always choose its built-in headers for some of the headers?

[palapapa]

I have found that for some headers like stddef.h, stdint.h, and stdbool.h, clangd will always choose the ones that are in its installation directory. For example, the path of stddef.h is shown as c:\Users\User\AppData\Roaming\Code\User\globalStorage\llvm-vs-code-extensions.vscode-clangd\install\15.0.3\clangd_15.0.3\lib\clang\15.0.3\include\stddef.h, while for stdio.h it's C:\mingw64\x86_64-w64-mingw32\include\stdio.h, which is correct. Here it does mention that clangd ships with its own built-in headers, so I don't know if this is the expected behavior.

My compile flags(specified through the fallbackFlags option in VSCode):

"clangd.fallbackFlags": [
    "-Weverything",
    "-Wno-used-but-marked-unused",
    "-Wno-declaration-after-statement",
    "-Wno-vla",
    "-Wno-missing-prototypes",
    "-Wno-c++98-compat",
    "-Wno-reserved-macro-identifier",
    "-Wno-padded",
    "-Wno-unsafe-buffer-usage",
    "-Wno-empty-translation-unit",
    "-target",
    "x86_64-w64-windows-gnu",
    "-xc",
    "-std=c17"
  ]

[HighCommander4]

Yes, this is expected. Headers in the built-in header directory are closely coupled to the compiler front-end, such that clang's built-in headers need to be used when parsing a file with the clang front-end.