How compiler make's sure that no data member state is changed in the const member function? (either in C++ or java)

Question

How can a C++ or Java compiler make sure that none of the member variables state is changed in a const member function (mutable is exceptional).

Will the compiler do something like putting the code in a non-writable code segment or something like that?

Answer 1

The compiler doesn't make sure. It can't, since there's no rule in the language that says that member variable state cannot change in a const member function. The only rule is that you cannot change the state through the this pointer (without casting away const).

Answer 2

For C++ const checking is done at compile time through the logic of the compiler. It will ensure that if a function is marked const then no changes will be made to the member variables. I don't think it has anything to do with the storage of the executable code.

For Java, I wasn't aware that there was the same const paradigm.