ccls is a C/C++/Objective-C language server.
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 ...
Hierarchies: call (caller/callee) hierarchy, inheritance (base/derived) hierarchy, member hierarchy
Document symbols and approximate search of workspace symbol
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 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.