I just found the video of showing the libclang and autocompletion.
see:
http://llvm.org/devmtg/2010-11/
and especially this section:
Quote
libclang: Thinking Beyond the Compiler
Doug Gregor, Apple Inc.
Also, some related stuff about code completion for vim:
https://github.com/Silex/clang_complete
there are some discussion to directly link to libclang instead of using clang.exe command line.
:D :D :D
whoa really cool, no need to compile the code to know where are the syntax errors, warnings and everything else :D