The functions can also be different if different compilation units were compiled using different compiler settings (or event different compilers). In Titus Win

The functions can also be different if different compilation units were compiled using different compiler settings (or event different compilers). In Titus Winters' recent Pacific++ talk[1], he pointed out that even something as simple as including an 'assert' statement will violate the ODR if some compilation units are compiled with 'debug' settings and some aren't. This can easily happen with build systems that cache compiled object files if changes in compilations flags don't automatically invalidate the cache. [1] https://youtu.be/IY8tHh2LSX4?t=900 https://youtu.be/IY8tHh2LSX4?t=900