Mutation testing has been out there for a while now, and it seems there are at least one or two commercial mutation testing frameworks for C/C++. Have you used them? What are yo
A straight forward python script for mutating c programs is available at:
https://github.com/parunbabu/mutate.py
the author says it works better if the code under test is de-commented and indented.
and it is also free and opensource ... i think this is what you are looking for.