| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // This file contains macros and macro-like constructs (e.g., templates) that |
| // are commonly used throughout Chromium source. (It may also contain things |
| // that are closely related to things that are commonly used that belong in this |
| // file.) |
| |
| #ifndef BASE_MACROS_H_ |
| #define BASE_MACROS_H_ |
| |
| #include <stddef.h> // For size_t. |
| |
| // Put this in the declarations for a class to be uncopyable. |
| #define DISALLOW_COPY(TypeName) \ |
| TypeName(const TypeName&) = delete |
| |
| // Put this in the declarations for a class to be unassignable. |
| #define DISALLOW_ASSIGN(TypeName) \ |
| void operator=(const TypeName&) = delete |
| |
| // A macro to disallow the copy constructor and operator= functions |
| // This should be used in the private: declarations for a class |
| #define DISALLOW_COPY_AND_ASSIGN(TypeName) \ |
| TypeName(const TypeName&); \ |
| void operator=(const TypeName&) |
| |
| // A macro to disallow all the implicit constructors, namely the |
| // default constructor, copy constructor and operator= functions. |
| // |
| // This should be used in the private: declarations for a class |
| // that wants to prevent anyone from instantiating it. This is |
| // especially useful for classes containing only static methods. |
| #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ |
| TypeName() = delete; \ |
| DISALLOW_COPY_AND_ASSIGN(TypeName) |
| |
| // The arraysize(arr) macro returns the # of elements in an array arr. The |
| // expression is a compile-time constant, and therefore can be used in defining |
| // new arrays, for example. If you use arraysize on a pointer by mistake, you |
| // will get a compile-time error. For the technical details, refer to |
| // http://blogs.msdn.com/b/the1/archive/2004/05/07/128242.aspx. |
| |
| // This template function declaration is used in defining arraysize. |
| // Note that the function doesn't need an implementation, as we only |
| // use its type. |
| template <typename T, size_t N> char (&ArraySizeHelper(T (&array)[N]))[N]; |
| #define arraysize(array) (sizeof(ArraySizeHelper(array))) |
| |
| // Used to explicitly mark the return value of a function as unused. If you are |
| // really sure you don't want to do anything with the return value of a function |
| // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: |
| // |
| // scoped_ptr<MyType> my_var = ...; |
| // if (TakeOwnership(my_var.get()) == SUCCESS) |
| // ignore_result(my_var.release()); |
| // |
| template<typename T> |
| inline void ignore_result(const T&) { |
| } |
| |
| // The following enum should be used only as a constructor argument to indicate |
| // that the variable has static storage class, and that the constructor should |
| // do nothing to its state. It indicates to the reader that it is legal to |
| // declare a static instance of the class, provided the constructor is given |
| // the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a |
| // static variable that has a constructor or a destructor because invocation |
| // order is undefined. However, IF the type can be initialized by filling with |
| // zeroes (which the loader does for static variables), AND the destructor also |
| // does nothing to the storage, AND there are no virtual methods, then a |
| // constructor declared as |
| // explicit MyClass(base::LinkerInitialized x) {} |
| // and invoked as |
| // static MyClass my_variable_name(base::LINKER_INITIALIZED); |
| namespace base { |
| enum LinkerInitialized { LINKER_INITIALIZED }; |
| |
| // Use these to declare and define a static local variable (static T;) so that |
| // it is leaked so that its destructors are not called at exit. If you need |
| // thread-safe initialization, use base/lazy_instance.h instead. |
| #define CR_DEFINE_STATIC_LOCAL(type, name, arguments) \ |
| static type& name = *new type arguments |
| |
| } // base |
| |
| #endif // BASE_MACROS_H_ |