static code analysis
As every one knows: I am a fan of objective measurements in the quality and quantity of code. Another nice statistics-generator for such a task is: cppdepend (trial is free for the first month).
It can detect some mistakes and deviations from common coding guidelines (like MISRA) and supports your judgment with some figures.
Cullendula for instance has the estimated development effort of 13 days (right now, v0.4.1) and a technical debt-rating of A. Which is great! 🙂