defer macro thing

defer.cpp

#ifndef defer
// Defer macro/thing.
template<typename T>
struct ExitScope {
    T lambda;
    ExitScope(T lambda) : lambda(lambda) {}
    ~ExitScope() { lambda(); }
    ExitScope(const ExitScope&);
private:
    ExitScope& operator =(const ExitScope&);
};

class ExitScopeHelp {
public:
    template<typename T>
    ExitScope<T> operator+(T t) { return t; }
};

#define defer const auto& CONCAT(defer__, __LINE__) = ExitScopeHelp() + [&]()
#endif