Pre-processor symbols from external files are not recognized.

[jsandr]

I'm using kconfig which defines a lot of CONFIG_VARIABLE_XXX.
All of which are sourced in a .h file inside the project and repository.
Eclipse is configured to use this file in its index as pre-processor symbol > User > GNU C.

When switching to the LSP editor, these symbols are not recognized anymore.

[ghentschke]

Is the header file included somewhere in a projects header or source file?

You can tell clangd to consider this file by adding it to the .clangd configuration file in the project root. It's described here.