Modifying object's state from a 'const' method without of const_cast<>(this) hacks

buhurt.cc

#include <iostream>

class Foo {
    int bar;
    int &baz;
    
public:
    Foo() : bar(0), baz(bar) {
    }

    void doIt() const {
        baz++; // <<-- modifying object's state from a 'const' method!!111oneone
    }

    void printIt() const {
        std::cout << "bar: " << bar << ", baz: " << baz << std::endl;
    }
};

int main(int argc, char *argv[]) {
    Foo foo;
    
    foo.printIt();
    foo.doIt();
    foo.printIt();

    return 0;
}

ion:dmatveev ~/devel
λ g++ buhurt.cc && ./a.out
bar: 0, baz: 0
bar: 1, baz: 1