Matt Beaumont-Gay of Google talked at the LLVM compiler conference about how they parse, store, and analyze the output of diagnostics (code warnings/errors) produced by LLVM. Google's in-house build system stores the output of all shared code-bases that occur. Matt ended up writing a MapReduce and using thje LLVM/Clang output as its input. "We now have a daily batch job that crunches through all of the compiler stderr from the last day, parses out detailed, structured information about the diagnostics that Clang produced, and writes the information into a database for later analysis."
For those interested, there are PDF slides on how Google leverages LLVM/Clang diagnostics and the most common compiler errors they hit with their internal code-bases.