[clangd-dev] #line directives not considered in clangd

[Sam McCall via clangd-dev]

FYI this mailing list is going away very soon (hours), replaced by
llvm.discourse.group.

Clangd handles locations in many places for various features - are you only
concerned about diagnostic locations or other features too?
It'd be useful to file a bug with details (a minimal example, how you
expect it to behave).
https://github.com/clangd/clangd

However I can imagine what you want may be a lot of work/infeasible:

- Clang only needs to print the filenames where it claims the source is
from, while clangd needs to point at a location in an actual file that the
editor will display. In general #line directives can (and do!) point at
files that don't exist or are out-of-sync with the files we're parsing.

- Clangd is designed to be used interactively while editing. If diagnostics
appear in foo.newlang, but editing foo.newlang doesn't cause them to
update, this is confusing.

- Clangd manipulates locations for output in many places for various
features. It's likely we'd need to add #line handling on a case-by-case
basis to each feature (many features require locations/ranges to properly
nest, which #line doesn't guarantee).

- Clangd really targets C-family languages supported by clang - doing small
cleanups to better support other use cases makes sense, but we can't really
justify adding much complexity for this.


On Tue, Feb 1, 2022 at 6:38 PM Benedikt Weiß via clangd-dev <
clangd-dev at lists.llvm.org> wrote:

> Hello,
>
> I am currently using the clangd for writing my own language server
> implementation for a new programming language, let's call it newlang.
>
> In this new programming language, it is possible to write C++ source
> code in specific places, so it is possible to embed C++ code in specific
> syntax constructs. Afterwards the files are compiled to C++ to use the
> normal C++ toolchain.
>
> As you can imagine, the embedded C++ from the original file is now also
> contained in the generated C++ file but in other places (at other line
> numbers etc because of additional generated C++ code). So, the embedded
> C++ source code which was at, for example, line 52 (in the original file
> of the new programming language) is now at line 132 in the generated C++
> file.
>
> To generate meaningful compiler messages, those places in the C++ file
> are annotated with #line directives which link back to the original file
> because you do not want to edit and analyze *generated* files but the
> original source file in the new programming language.
>
> So, if I am using the standalone clang compiler, everything is correct
> and as expected:
>
> benedikt at fedora:~$ clang /path/to/example_file.cxx
> /path/to/example_file.newlang:39:9: warning: expression result unused
> [-Wunused-value]
>
> because of something like
>
> #line 22 "/path/to/example_file.newlang"
>
> in the generated example_file.cxx. This is correct because the
> example_file.cxx is generated from the example_file.newlang and "links
> back" to the original location of the C++ source code, via those #line
> directives.
>
> Now my question is: How can I get the *clangd* to recognize/consider
> #line directives? I could not get it to work. clangd seems to ignore
> them. clangd compiles the file correctly and generates
> "publishDiagnostics" with the same warning and error messages etc but
> without considering the #line directives, it only considers the line
> numbers from the C++ file (in this example_file.cxx it would be like
> line 132).
>
> I also tried "-fuse-line-directives" but without success.
>
>
> Thanks you for your time.
>
>
>
>
> With kind regards,
>
>
> Benedikt Weiß
>
>
>
>
>
> _______________________________________________
> clangd-dev mailing list
> clangd-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/clangd-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/clangd-dev/attachments/20220201/c009b4a5/attachment-0001.html>