Autocompletion in Vim

Try YouCompleteMe. It uses Clang through the libclang interface, offering semantic C/C++/Objective-C completion. It's much like clang_complete, but substantially faster and with fuzzy-matching.

In addition to the above, YCM also provides semantic completion for C#, Python, Go, TypeScript etc. It also provides non-semantic, identifier-based completion for languages for which it doesn't have semantic support.

There’s also clang_complete which uses the clang compiler to provide code completion for C++ projects. There’s another question with troubleshooting hints for this plugin.

The plugin seems to work fairly well as long as the project compiles, but is prohibitively slow for large projects (since it attempts a full compilation to generate the tags list).