ccls, which originates from cquery, is a C/C++/Objective-C language server.

Its features include:
- code completion (with both signature help and snippets)
- definition/references, and other cross references
- cross reference extensions: $ccls/call $ccls/inheritance
  $ccls/member $ccls/vars ...
- formatting
- hierarchies: call (caller/callee) hierarchy, inheritance
  (base/derived) hierarchy, member hierarchy
- symbol rename
- document symbols and approximate search of workspace symbol
- hover information
- diagnostics and code actions (clang FixIts)
- semantic highlighting and preprocessor skipped regions
- semantic navigation: $ccls/navigate

It has a global view of the code base and support a lot of cross reference
features, see https://github.com/MaskRay/ccls/wiki/FAQ.
It starts indexing the whole project (including subprojects if exist)
parallelly when you open the first file, while the main thread can serve
requests before the indexing is complete. Saving files will incrementally
update the index.