[ruediger]

I guess the reason for Google to start contributing to Clang and using it for their tools is the availability of the frontend. As far as I know the GCC developers made it extra hard to separate the frontend from the compiler because they feared that people would use it on proprietary backends. But this really left us in a situation were for decades people couldn't work on creating amazing static analysis, autocompletion, refactoring tools for C and C++. In the end this decision probably did more damage to the free software movement. GCC now comes with a plugin interface and with the Clang frontend available I hope that this will change quickly.