General Motors, the nation’s largest automaker and for decades an icon of American manufacturing, stood on the brink of a bankruptcy filing and a de facto government takeover on Monday. A bankruptcy petition will be filed at 8 a.m., according to a source with direct knowledge of the bankruptcy proceedings. President Barack Obama will address the nation shortly before noon on Monday to explain the rationale for the filing, and his hopes that this is the best route for a turnaround, two officials close to the situation told CNN.