What are the semantics of a const member function?

Question

I understand that the function is not allowed to change the state of the object, but I thought I read somewhere that the compiler was allowed to assume that if the function

Answer 1

In this context, a const member function means that this is treated as a const pointer also. In practical terms, it means you aren't allowed to modify the state of this inside a const member function.

For no-side-effect functions (i.e., what you're trying to achieve), GCC has a "function attribute" called pure (you use it by saying __attribute__((pure))): http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html