Method add

src/butil/thread_local.cpp:45–56

    }

    int add(Fn fn, void* arg) {
        try {
            if (_fns.capacity() < 16) {
                _fns.reserve(16);
            }
            _fns.emplace_back(fn, arg);
        } catch (...) {
            errno = ENOMEM;
            return -1;
        }
        return 0;
    }

    void remove(Fn fn, void* arg) {
        std::vector<Pair>::iterator