[Help wanted]: can I use g++ with clangd?
reddit / emacs

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Financial-Bet2253 · 2022-11-14 14:09

I use lsp-mode && c++. For some reason, my project can only built with
g++. But I use clangd as lsp server. I found that there's a parameter
called "query-driver", would it take effect if I use g++ as query
driver?
What's more, in compile_commands.json file, I replace the compiler
clang++ with g++, will it bother?

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yyoncho · 2022-11-14 15:16

I would ask that question in clangd's discord channel.

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CorysInTheHouse69 · 2022-11-14 16:26

Yes you can. They are not mutually exclusive

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yapfff · 2022-11-14 16:29

I use clangd with gcc (not g++, but same toolchain) every day in an
embedded context. It works fine. clangd is supposed to adapt itself to
the compiler used as defined in the compilation database
(compile_commands.json).

In an embedded context, I had an issue with a gcc option clangd didn't
understand. You can deal with this easily using a `.clangd`
configuration, mine contain for example:

    CompileFlags:
        Remove: -f*

This remove all the optimization options (including the problematic
one), the ones starting with "-f". They're not useful for LSP
functions and some may be problematic. But overall the clang and
clangd have very good compatibility with the GCC toolchain.

Hope that helps, if it's really C++ specific there may be other
"gotcha" I don't know about.

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ForkInBrain · 2022-11-14 17:37

> But I use clangd as lsp server.

That is fine, but know that the warnings, errors, etc., the LSP
generates will come from clang.  It will not run gcc.

> I found that there's a parameter called "query-driver", would it
take effect if I use g++ as query driver?

This is only about asking gcc where the system headers are, so clangd
can find them.  See https://clangd.llvm.org/guides/system-headers

> What's more, in compile_commands.json file, I replace the compiler
clang++ with g++, will it bother?

clangd will ignore that change completely and always use itself as the
"compiler".

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Financial-Bet2253 · 2022-11-15 02:07

Thanks. You said "I had an issue with a gcc option clangd didn't
understand", what does it mean? Will clangd report some error?

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Financial-Bet2253 · 2022-11-15 02:08

Perfect answer! So clangd just ignore my g++ compiler🤣

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yapfff · 2022-11-15 12:45

It was quite some time ago and I forgot the specifics... But I had to
add this filtering clangd configuration to get a smooth operation.

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Thaodan · 2022-11-15 21:03

Yeah probably also ignores any GCC ism's.

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Thaodan · 2022-11-15 21:04

I wouldn't advice discord with all the privacy issues.
The IRC or Matrix channel would be better I think.

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yyoncho · 2022-11-15 21:41

Do they have irc/matrix channels?

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Financial-Bet2253 · 2022-11-16 02:41

i have one more question. If i don't have clang && clang++ installed,
how could clangd use clang?

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Thaodan · 2022-11-16 08:21

You can't clangd depends on clang.

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Financial-Bet2253 · 2022-11-16 08:24

I mean if there's only gcc&&g++ on my linux system, how could clangd
provide the functionality like semantic checking?

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Thaodan · 2022-11-16 20:11

You  can't clangd depends on libclang.