Method alive

tests/constructor_stats.h:131–140

    }

    int alive() {
        gc();
        int total = 0;
        for (const auto &p : _instances) {
            if (p.second > 0) {
                total += p.second;
            }
        }
        return total;
    }

    void value() {} // Recursion terminator
    // Takes one or more values, converts them to strings, then stores them.