Method str_value

tests/test_virtual_functions.cpp:362–362

        OverrideTest() = default;
        OverrideTest(const OverrideTest &) = delete;
        virtual std::string str_value() { return v; }
        virtual std::string &str_ref() { return v; }
        virtual A A_value() { return a; }
        virtual A &A_ref() { return a; }