Add a --query-driver flag to clangd-indexer

[tetsuo-cpp]

Hi there! I'm trying to build a static index for a codebase that I'm cross-compiling.

I believe that in order to use clangd in this situation, you need to provide a path to the compiler with the --query-driver flag so that clangd can find the appropriate headers. However, there's no such flag for clangd-indexer. So when I try to build the index, I'm seeing a lot of include errors as it's not finding the correct headers.

Is there a way to get this to work that I've missed? And if not, would you accept a patch to add a flag like this to clangd-indexer?

[HighCommander4]

Is there a way to get this to work that I've missed?

The alternative to --query-driver is to specify your cross-compiler's system include paths manually.

You can run <cross-compiler> -E -v -xc++ - (this is what clangd does when --query-driver is specified; replace -xc++ with -xc if working on C code), look at the list of system include paths printed after #include <...> search starts here, and add a corresponding -isystem <path> to your source files' compile commands for each one.

Unfortunately, the simplest way to add those -isystem <path> flags would be using a clangd config file, but that's not hooked up for clangd-indexer either...

So that leaves you with arranging for your compile_commands.json to contain those -isystem flags, which may or may not be straightforward depending on how you're generating your compile_commands.json.

And if not, would you accept a patch to add a flag like this to clangd-indexer?

I don't call the shots so I can't guarantee that a patch would be accepted, but I think that would be a nice addition and fill a logical gap. I'm happy to provide guidance if you'd like to write a patch.