C++ finalizer like Go defer

finalize.h

#pragma once

#include <utility>

/**
 * Execute block on out of scope.
 *
 * Example:
 *
 *   auto file = open("file.txt");
 *   finalize { close(file); };
 *
 */
template <typename T>
class Finalizator {
public:
    Finalizator(T&& block)
        : block(std::move(block))
    {
    }

    Finalizator(const Finalizator&) = delete;

    ~Finalizator() { block(); }

private:
    T block;
};

#define CONCAT_IMPL__(s1, s2) s1##s2
#define CONCAT__(s1, s2) CONCAT_IMPL__(s1, s2)

#define finalize Finalizator CONCAT__(finalize_block_, __COUNTER__) = [&]

Usage example:

cout << "Opened" << endl;
finalize { cout << "Closed" << endl; };
throw "Bang!";