C++ performance of accessing member variables versus local variables

Question

Is it more efficient for a class to access member variables or local variables? For example, suppose you have a (callback) method whose sole responsibility is to receive dat

Answer 1

I'd prefer the local variables on general principles, because they minimize evil mutable state in your program. As for performance, your profiler will tell you all you need to know. Locals should be faster for ints and perhaps other builtins, because they can be put in registers.