1 // Copyright 2014 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // This file contains macros and macro-like constructs (e.g., templates) that 6 // are commonly used throughout Chromium source. (It may also contain things 7 // that are closely related to things that are commonly used that belong in this 8 // file.) 9 10 #ifndef BASE_MACROS_H_ 11 #define BASE_MACROS_H_ 12 13 #include <stddef.h> // For size_t. 14 15 #if defined(ANDROID) 16 // Prefer Android's libbase definitions to our own. 17 #include <android-base/macros.h> 18 #endif // defined(ANDROID) 19 20 // We define following macros conditionally as they may be defined by another libraries. 21 22 // Put this in the declarations for a class to be uncopyable. 23 #if !defined(DISALLOW_COPY) 24 #define DISALLOW_COPY(TypeName) \ 25 TypeName(const TypeName&) = delete 26 #endif 27 28 // Put this in the declarations for a class to be unassignable. 29 #if !defined(DISALLOW_ASSIGN) 30 #define DISALLOW_ASSIGN(TypeName) \ 31 void operator=(const TypeName&) = delete 32 #endif 33 34 // A macro to disallow the copy constructor and operator= functions. 35 // This should be used in the private: declarations for a class. 36 #if !defined(DISALLOW_COPY_AND_ASSIGN) 37 #define DISALLOW_COPY_AND_ASSIGN(TypeName) \ 38 TypeName(const TypeName&) = delete; \ 39 void operator=(const TypeName&) = delete 40 #endif 41 42 // A macro to disallow all the implicit constructors, namely the 43 // default constructor, copy constructor and operator= functions. 44 // 45 // This should be used in the private: declarations for a class 46 // that wants to prevent anyone from instantiating it. This is 47 // especially useful for classes containing only static methods. 48 #if !defined(DISALLOW_IMPLICIT_CONSTRUCTORS) 49 #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ 50 TypeName() = delete; \ 51 DISALLOW_COPY_AND_ASSIGN(TypeName) 52 #endif 53 54 // The arraysize(arr) macro returns the # of elements in an array arr. The 55 // expression is a compile-time constant, and therefore can be used in defining 56 // new arrays, for example. If you use arraysize on a pointer by mistake, you 57 // will get a compile-time error. For the technical details, refer to 58 // http://blogs.msdn.com/b/the1/archive/2004/05/07/128242.aspx. 59 60 // This template function declaration is used in defining arraysize. 61 // Note that the function doesn't need an implementation, as we only 62 // use its type. 63 #if !defined(arraysize) 64 template <typename T, size_t N> char (&ArraySizeHelper(T (&array)[N]))[N]; 65 #define arraysize(array) (sizeof(ArraySizeHelper(array))) 66 #endif 67 68 // Used to explicitly mark the return value of a function as unused. If you are 69 // really sure you don't want to do anything with the return value of a function 70 // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: 71 // 72 // std::unique_ptr<MyType> my_var = ...; 73 // if (TakeOwnership(my_var.get()) == SUCCESS) 74 // ignore_result(my_var.release()); 75 // 76 template<typename T> 77 inline void ignore_result(const T&) { 78 } 79 80 // The following enum should be used only as a constructor argument to indicate 81 // that the variable has static storage class, and that the constructor should 82 // do nothing to its state. It indicates to the reader that it is legal to 83 // declare a static instance of the class, provided the constructor is given 84 // the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a 85 // static variable that has a constructor or a destructor because invocation 86 // order is undefined. However, IF the type can be initialized by filling with 87 // zeroes (which the loader does for static variables), AND the destructor also 88 // does nothing to the storage, AND there are no virtual methods, then a 89 // constructor declared as 90 // explicit MyClass(base::LinkerInitialized x) {} 91 // and invoked as 92 // static MyClass my_variable_name(base::LINKER_INITIALIZED); 93 namespace base { 94 enum LinkerInitialized { LINKER_INITIALIZED }; 95 96 // Use these to declare and define a static local variable (static T;) so that 97 // it is leaked so that its destructors are not called at exit. If you need 98 // thread-safe initialization, use base/lazy_instance.h instead. 99 #if !defined(CR_DEFINE_STATIC_LOCAL) 100 #define CR_DEFINE_STATIC_LOCAL(type, name, arguments) \ 101 static type& name = *new type arguments 102 #endif 103 104 } // base 105 106 #endif // BASE_MACROS_H_ 107
