scopeguard.hpp

#ifndef SCOPEGUARD_HPP
#define SCOPEGUARD_HPP
    
#include <functional>

#ifndef __has_feature
    #define __has_feature(x) 0
#endif

namespace detail
{
    template<typename F>
    class scopeguard_impl
    {
        public:
            explicit scopeguard_impl(F&& f_)
                : f(std::forward<F>(f_)), dismissed(false)
            {
            }

            // Note: defining a move constructor inhibits auto-generation of copy constructor and copy assignment operator.
            scopeguard_impl(scopeguard_impl&& rhs)
                : f(std::move(rhs.f)), dismissed(std::move(rhs.dismissed))
            {
                rhs.dismiss();
            }
        
#if __has_feature(cxx_reference_qualified_functions)
            scopeguard_impl& operator=(scopeguard_impl&& rhs) &
#else
            scopeguard_impl& operator=(scopeguard_impl&& rhs)
#endif
            {
                this->f = std::move(rhs.f);
                this->dismissed = std::move(rhs.dismissed);
                rhs.dismiss();
                return *this;
            }
    
            ~scopeguard_impl()
            {
                if (!this->dismissed)
                {
                    this->f();
                }
            }
        
            void dismiss()
            {
                this->dismissed = true;
            }

        private:
            F f;
            bool dismissed;
    
            // Prevent scopeguard from being new'ed.
            void* operator new(std::size_t) = delete;
            void* operator new[](std::size_t) = delete;
            void operator delete(void*) = delete;
            void operator delete[](void*) = delete;
    };
}

template<typename F>
detail::scopeguard_impl<F> scopeguard(F&& f)
{
    return detail::scopeguard_impl<F>(std::forward<F>(f));
}

#define SCOPEGUARD_PP_CAT_IMPL(x, y) x##y
#define SCOPEGUARD_PP_CAT(x, y) SCOPEGUARD_PP_CAT_IMPL(x, y)
#define at_scope_exit(f) \
    __attribute__((unused)) const auto SCOPEGUARD_PP_CAT(scopeguard, __COUNTER__) = scopeguard((f));

#endif // SCOPEGUARD_HPP