To use this you'll need SableCC 3.
java -jar sablecc/lib/sablecc.jar objc2.sablecc3
And of course you'll have to write code that instantiates Parser and does something useful with it.
C source files using typedef cannot be parsed with parser that has lexer and parser nicely separated. As a temporary workaround, I've extended SableCC's parser to recognize some basic Cocoa types — see net/pornel/objc2/hack/PreprocLexer.java.
Grammar skips preprocessor rules. It's a good idea to use existing preprocessor with it, e.g.:
gcc -E test.m