board support package includes about clangd HOT 3 OPEN

why wouldn't clangd use those flags, nevertheless clang doesn't recognize them, for queries for query driver in order to extract more information about compiler's toolchain?

Good question!

Clangd only forwards arguments from the command line passed to the clang driver to parse the file, to the command line used for --query-driver, for a small set of allow-listed arguments known to impact the system includes. This is mainly so it can effectively cache the results of --query-driver rather than having to run it for every file in the project.

We've added arguments to that list before, for example see the recent addition of -specs in llvm/llvm-project#70285.

However, one difference here is that -specs is recognized by the clang driver (even if it doesn't have any effect).

If we were to add e.g. -qbsp to the list, now --query-driver will get it, but you'll still have the problem that the clang driver will also get it and it will issue an error about it.

(Though I note the error is not a fatal error... so maybe an ability to suppress that error would be sufficient? We have a mechanism to suppress diagnostics in general (https://clangd.llvm.org/config.html#suppress), but it doesn't currently work for driver diagnostics due to #1142.)

Another approach that could be considered is to add support for the clang driver to syntactically recognize the affected flags, even if it ignores them, similar to -specs.

from clangd.

clangd is a clang-based tool so its support, in terms of things like targets and cpus, is generally determined by what clang supports.

The general procedure is:

• figure out what set of flags causes clang to successfully compile the code
• make sure clangd is using those same flags

If the code is not portable to clang / not supported by clang then clangd may not work properly either (though you may be able to find workarounds like manually adding flags that get it to work well enough for editing purposes)

from clangd.

@HighCommander4 thanks for your answer, seems to be fair. on other hand, why wouldn't clangd use those flags, nevertheless clang doesn't recognize them, for queries for query driver in order to extract more information about compiler's toolchain?

from clangd.