This originates from cquery, and is a server implementing Language Server Protocol for C/C++/Objective-C. It supports:

* 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