% id = "01H9R1KJESR2F420HE67HW4AVR"
- design lessons from the best programming language of all time that everyone loves (not really)

% id = "programming/cxx/access-modifiers-as-labels"
+ access modifiers as labels (`private:`, `protected:`, and `public:`)

    % id = "01H9R1KJES39Z6RBCKY4E71PYD"
    - although Java and C#'s approach to symbol privacy may be verbose, it has one great advantage: it is stateless.

    % id = "01H9R1KJES17626QXYEGM7XBC7"
    - the way they're implemented in C++, it's essentially a bit more parsing state you have to keep track of

        % id = "01H9R1KJESG4K8T1K1G36T7HBP"
        - and you know what other parsing state you have to keep track of in C++? - that's right, the preprocessor.\
        access modifiers, like all tokens, are affected by the preprocessor, and you have to take that into account.

            % id = "01H9R1KJESJ0G0VQAW994ZHR0S"
            - take the following example:
            ```cpp
            class ComfyZone
            {
                std::vector<SoftBed> _soft_beds;

            #if ENABLE_HUGS

            public:
                void hug(Person& person);

            #endif

                int _remaining_hugs = 10;
            };
            ```

                % id = "01H9R1KJESDDX4089WVHVV8N3H"
                + although quite contrived, it illustrates the problem pretty well

                    % id = "01H9R1KJESD2KED5TAFBY426A6"
                    - (before you ask, `_remaining_hugs` needs to be always present because it has to be (de)serialized no matter if hugging functionality is compiled in. otherwise we'd get data loss.)

                % id = "01H9R1KJESES27VKVW4A0ZVM11"
                - we intended for `_remaining_hugs` to be private, but if hugs are enabled, it becomes public.

                    % id = "01H9R1KJESTKW90R788SSPMNC6"
                    - this can be _very_ hard to spot if you have a big class with lots of declarations inside.

            % id = "01H9R1KJESCJ3VC8ATPYFDCPSP"
            - this can be worked around by banning access modifiers from appearing in `#ifdef`s, but you have to *realize* that this might happen

                % id = "01H9R1KJES4ZYHVADDF80WAXH6"
                - and I've seen instances of this exact thing occurring in the Unreal Engine codebase, which is *full* of long lists of declarations (made even longer by the prevalence of `UPROPERTY()` specifiers)

    % id = "01H9R1KJES182MCV2V0A4VHKKX"
    - even if we didn't have the preprocessor, that access modifier is state _you_ have to keep track of

        % id = "01H9R1KJESH7PWNKCKW3H0WJHW"
        - I very often find myself needing to scroll upward after <kbd>Ctrl</kbd>-clicking on a field or function declaration, just to find out if I can use it

            % id = "01H9R1KJESFE6F1D4J5PA5Q381"
            - (thankfully IDEs are helpful here and Rider shows you a symbol's visibility in the tooltip on hover, but I don't have Rider on code reviews)