system/ulib/fbl/include/fbl/macros.h

// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <type_traits>

// Macro used to simplify the task of deleting all of the default copy
// constructors and assignment operators.
#define DISALLOW_COPY_ASSIGN_AND_MOVE(_class_name)       \
    _class_name(const _class_name&) = delete;            \
    _class_name(_class_name&&) = delete;                 \
    _class_name& operator=(const _class_name&) = delete; \
    _class_name& operator=(_class_name&&) = delete

// Macro used to simplify the task of deleting the non rvalue reference copy
// constructors and assignment operators.  (IOW - forcing move semantics)
#define DISALLOW_COPY_AND_ASSIGN_ALLOW_MOVE(_class_name) \
    _class_name(const _class_name&) = delete;            \
    _class_name& operator=(const _class_name&) = delete

// Macro used to simplify the task of deleting the new and new[]
// operators. (IOW - disallow heap allocations)
#define DISALLOW_NEW                       \
    static void* operator new(size_t) = delete;   \
    static void* operator new[](size_t) = delete

// Macro for defining a trait that checks if a type T has a method with the
// given name. This is not as strong as using is_same to check function
// signatures, but checking this trait first gives a better static_assert
// message than the compiler warnings from is_same if the function doesn't
// exist.
// Note that the resulting trait_name will be in the namespace where the macro
// is used.
//
// Example:
//
// DECLARE_HAS_MEMBER_FN(has_bar, Bar);
// template <typename T>
// class Foo {
//   static_assert(has_bar<T>::value, "Foo classes must implement Bar()!");
//   // TODO: use 'if constexpr' to avoid this next static_assert once c++17
//   lands.
//   static_assert(is_same<decltype(&T::Bar), void (T::*)(int)>::value,
//                 "Bar must be a non-static member function with signature "
//                 "'void Bar(int)', and must be visible to Foo (either "
//                 "because it is public, or due to friendship).");
//  };
#define DECLARE_HAS_MEMBER_FN(trait_name, fn_name)                      \
    template <typename T>                                               \
    struct trait_name {                                                 \
    private:                                                            \
    template <typename C> static std::true_type test( decltype(&C::fn_name) ); \
    template <typename C> static std::false_type test(...);           \
                                                                        \
    public:                                                             \
    static constexpr bool value = decltype(test<T>(nullptr))::value;    \
    }

// Similar to DECLARE_HAS_MEMBER_FN but also checks the function signature.
// This is especially useful when the desired function may be overloaded.
// The signature must take the form "ResultType (C::*)(ArgType1, ArgType2)".
//
// Example:
//
// DECLARE_HAS_MEMBER_FN_WITH_SIGNATURE(has_c_str, c_str, const char* (C::*)() const);
#define DECLARE_HAS_MEMBER_FN_WITH_SIGNATURE(trait_name, fn_name, sig)            \
template <typename T>                                                             \
struct trait_name {                                                               \
private:                                                                          \
    template <typename C> static std::true_type test( decltype(static_cast<sig>(&C::fn_name)) ); \
    template <typename C> static std::false_type test(...);                     \
                                                                                  \
public:                                                                           \
    static constexpr bool value = decltype(test<T>(nullptr))::value;              \
}