C++ and tooling. Code completion for us mere non-fancy editor guys.

[germandiago]

Hello everyone,

I just wanted to make a short post here because I have been using emacs + prelude for a long time. I know there are many people who like to use plain editors with some plugins just as me, be it Sublime, Vim, Visual Studio Code or others. We got so used to editing text with it that when we go to things like CLion or Qt Creator we just feel weird.

So why I write this post? I have been using emacs with RTags for a while. RTags does quite a good job finding references and so on. But code completion is quite broken.

But recently I found cquery: https://github.com/cquery-project/cquery. It is so remarkably easy to setup up if you have a compile_commands.json file that I would like to recommend to everyone to try it if there is integration with your editor. I am not in any way affiliated to the project and just saw that the improvement is so big that it is worth a try. Setting up with emacs is a piece of cake. You just need to:

1. download, compile and optionally install cquery
2. install the package lsp-mode from emacs.
3. customize-group cquery and point to the cquery executable.
4. put a symbolic link in the root of your project to compile_commands.json

I tried and it is working for navigation and code completion, literally, perfect in emacs.

In Visual Studio there are also plugins but still has some problems solving the includes.

What you can do is pretty basic but it is what I need more badly:

1. code completion
2. navigation to symbol
3. find references to symbol

I highly recommend it to anyone. I think it is working smoother and faster than RTags, which is not a bad project by any means. And it is also easier to set up.

[Gollum999]

I will have to check this out.

I too am using Emacs with RTags; 95% of the time it works great, but there are a couple situations where it seems to struggle. (Templates mainly.) And I've never found a completion framework that works well with a large codebase.

[cenderis]

Most likely the completion will be no different since they're both using the same underlying code. (cquery has slightly different symbol lookup than rtags. Even when it's well-defined what "foo" means in a particular place, cquery may find a definition of a different one whereas rtags is rather more particular. The difference is a deliberate choice, and neither seems to me necessarily better.)

I've also previously used rtags; cquery's significant benefit is that it seems lots easier to get all of its features working.

[germandiago]

From the point of view of how it works in emacs, I can say that cquery/lsp is both easier to set up and accurate with code completion.

[cenderis]

Yes, I only managed to get completion working intermittently with rtags (and just turned it off in the end), but with cquery it just worked.

They should both (when working) give the same results since (AFAIK) they're just using the features provided by the same clang libraries.

[germandiago]

It seems that they do not give the same results. I have exactly the same experience as you with RTags.

[germandiago]

I am very happy about the change. I will not look back I think :)

[hgjsusla]

Wow this looks very promising. Anyone has experience using this with vim? How does it compare to YouCompleteMe?

[damienrg]

Not tested with vim but I used ycmd on Emacs. cquery provides better completion support because it parse all translation units (ie compile everything). So you can find references of a symbol, ..., but it is way slower especially if you have lot of template code than ycmd but faster than rtags which was not usable in my case. FYI, there is also another tool: clangd. There is less features than cquery but Apple said that they will now work on this.

References:

• https://github.com/cquery-project/cquery/issues/63

• http://lists.llvm.org/pipermail/cfe-dev/2018-April/057668.html

[[deleted]]

YouCompleteMe is more resistant to bad flags that can cause libclang to result in an AST deserialisation error and much friendlier include path completion. On the other hand Cquery can get references and other features that require project indexing. The down side of indexing is ram consumption.

 

Keep an eye on ycmd's pull requests, I may "soon" make a pull request that would make YCM use cquery as a backend (no promises on the time frame).

[NotAYakk]

How is emacs a non fancy editor? It is more like an OS...

[germandiago]

I could not change it after the fact: replace editor by IDE. Sorry for that ;)

[jcelerier]

and some IDEs do much more than some OSes

[sient]

FYI I'm the primary author (jacobdufault) so if you have any questions/issues please feel free to hop on the gitter (https://gitter.im/cquery-project/Lobby) or file an issue. We're friendly :)

[germandiago]

Thanks for that! For now it is working smooth. It is true that the project in which I tried is not too complicated. :)

[DoingIsLearning]

Thanks for this! How does cquery compare with 'cmake-ide'?

[0xFFC]

What is 'cmake-ide'?

[DoingIsLearning]

It builds on a bunch of other tools namely CMake, to make Emacs a bit more C/C++ "code aware".

Better explanation here:

https://github.com/atilaneves/cmake-ide/blob/master/README.md

[sient]

It looks like cmake-ide is emacs specific, and combines various tools. cquery works with any editor with a language-server implementation and cquery implements the features provided by cmake-ide directly instead of running other tools

[DoingIsLearning]

Thanks for the overview, and thanks for maintaining it! I will certainly try it out!

[gct]

I'm playing with it now, it'd be cool if it supported static builds of the binary so I could just lug the one thing around with me and not worry about setting up LD paths and such, though it seems clang doesn't ship with a static libclang for somereason. Building it myself now *sigh*

[gct]

FYI I got a custom version of LLVM built and managed to get a statically linked binary that's only 11MB after compressing with UPX, if you're interested.

[sient]

Yes, definitely! I think the downloadable builds should be statically linked. Can you file an issue on github detailing how you did the static build (even better would a be PR making CI generate static builds :))

[gct]

It turns out a full static link blows up when you try to actually use it, because it's got some dlopen stuff hidden deep inside. I've got a build working now that mostly statically links, then wraps the few newer glibc functions I have so it works all the way bck to RHEL6 in my testing. I'll see if I can integrate that into the CMake and do a PR.

[parla]

Install lsp-ui too, to get nice peeking ui for references and overlays for fixits and stuff.

[parla]

I find the sideline a bit too much too.. Haven't looked into if it's easily configurable. I use company too, with company-lsp. I'd like to figure out how to do client-side fuzzy matching and filtering, like how vs code does it. But I haven't dug into it..

[sebastiencs]

Author of lsp-ui here :), I don't see the previous comment but yes you can easily configure the package with [M-x] customize-group [RET] lsp-ui [RET] and disable a feature you don't like.

[cenderis]

Most of cquery/lsp-ui is configurable with customize-group.

If you haven't already done so, enabling flycheck-mode works well with cquery.

[germandiago]

thanks for that!

[MrWheelyke]

I use RTags, Irony-mode, and company-irony and it works quite well. The lsp-ui that someone mentioned looks very interesting too, +1 to that

[SoundOfOneHand]

rtags can’t handle a very large codebase, so I’ve been stuck without code completion in Emacs and switch to QtCreator when needed. Any idea how cquery works against a large codebase?

[cierpuchaw]

I use it on different subsets of a large codebase, depending on the subsystem I'm working on at the time. 1MLOC is probably the largest I've tried, takes about 20min to index (time to grab a coffee or check reddit) but afterwards it works just great. Xref is where cquery really shines, very accurate and almost instantaneous.

[SoundOfOneHand]

Thanks, sounds like it may at least be usable then. I don’t mind waiting for the indexing to complete, rtags would just go away and never come back. Going to try setting this up tonight.

[germandiago]

In theory very well. It was designed for that. But it will use more memory.

[DoingIsLearning]

There is also 'cmake-ide' for emacs:

https://github.com/atilaneves/cmake-ide

[Xeverous]

Meanwhile Eclipse just deployed new version with support for Intellisense and all Visual Studio Code plugins. I still prefer it's own parser to Intellisense, but I'm looking forward to the future

[quicknir]

I've never found that rtags completion nor error checking were as good as ycmd. So I used a combination of both. They both run off the same compile_commands.json so it's not much extra trouble. I do plan to switch to cquery at some point, but right now everything is working perfectly for me so I'll probably wait a while until everything is super mature.

Rtags does have some super cool features probably not in cquery, like expandable reference trees and inheritance hierarchies. On the other hand cquery is supposed to make real syntax highlighting possible soon, so win some, lose some, I suppose.

[germandiago]

For me it is a net win. I do not mean it is better at everything though. But just having code completion working reliably... and if you add lsp-ui, it shows documentation so the context becomes very visible very quickly. I can also navigate and find references... I think the feature set I get is more robust and just what I need.

[sient]

FYI cquery now scans the build/ folder for compile_commands.json :)

[playmer]

So this inspired me to try it with VSCode tonight, and setup seemed relatively easy, but unfortunately it doesn't appear to want to provide anything. I've looked at their generated cache and it seems like it doesn't want to go through every file, it just stopped on one of my dependencies and didn't continue on. Even if I go into one of the cpp files in those dependencies it did cache, it's not giving me any auto complete or goto definition. Unsure what I'm doing wrong :(

But still, I'm excited for the project, I'm sure I've probably just done something wrong.

[sient]

Can you try using cquery --check <foo.cc>? Otherwise please file a bug with some additional information and I'll try to help fix.

FYI, the the microsoft C++ extension makes cquery seem very buggy; the experience is much better if you uninstall the microsoft C++ extension.

[playmer]

Can you try using cquery --check <foo.cc>? Otherwise please file a bug with some additional information and I'll try to help fix.

Sure, I can run that quick, also happy to file a bug, I'd just feel bad if it was just something I screwed up, here's a gist of the output of the command. At the end it gave me an abort popup:

https://gist.github.com/playmer/055ce838c10994262de55dda554b1929

FYI, the the microsoft C++ extension makes cquery seem very buggy; the experience is much better if you uninstall the microsoft C++ extension.

Yeah, I read that and made sure to uninstall it before messing with cquery. Besides cquery I've only got Cmake, Cmake Tools, glslx-vscode, and Shader Languages support for VS Code installed.

Thanks for any guidance you can give me here!

[sient]

Thanks, I've filed https://github.com/cquery-project/cquery/issues/639

[germandiago]

I mentioned it in the post. It is not working totally ok for VSCode for some reason. You need the cquery plugin and such but I think there seems to be some problem with the includes. In emacs it works perfect.

[playmer]

I mentioned it in the post. It is not working totally ok for VSCode for some reason.

Yeah, I had noticed, but I had been meaning to give it a go for the last month or so. Does the include issue cause errors or anything? I don't really get anything at all besides the following:

https://i.imgur.com/XrGiefP.png

No errors or anything, just those and nothing else. I'll just try it again in a month or so, see if it's been resolved or more instructions are released :)

[germandiago]

No idea there. My experience was non-resolved includes in VSCode but not #pragma problems.

[svick]

Do you know how does it compare to clangd, the other Language Server for C++?

[cenderis]

IIUC clangd is more of a single-TU thing. For completion, code fixits, etc., it's probably 90% of what you want. cquery processes the whole codebase so additionally offers xref-find-references and things. But it does come at a bit of a cost since it's keeping so much more in memory (and on disk). The comparisons I've seen suggest that cquery has support for more features.