Array constants can only be used in initializers

chenleiwei 2011-01-07 04:46:39
我分着写两句代码:
Object[] obje=null;
obje={"1"};
这时就会报Array constants can only be used in initializers，为什么啊？
这样写就没有错：Object[] obje={"1"};
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qybao 2011-01-07
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Object[] obje=null;
obje={"1"}; //这样的赋值只有在声明的同时可以使用，即Object[] obje = {"1"};是可以的
//除此之外的赋值，就要针对数组元素分别赋值或用new的方式或引用别的数组对象，即
Object[] obje=null;
obje=new Object[]{"1"}; //这样是可以的
//或者
obje=new Object[1];
obje[0]="1";
//或者
Object obje2={"1"};
obje=obje2;
amos1989 2011-01-07
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数组必须先初始化，再使用。。


初始化方式，你自己看下书
龙四 2011-01-07
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数组的几种初始化方式，java基础书上都有的

就是没有obje={"1"};的方式。。。
steely_chen 2011-01-07
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Object[] obje={"1"};
声明并指定类型赋值
Google C++ Style Guide(Google C++编程规范）高清PDF
Table of Contents Header Files The #define Guard Header File Dependencies Inline Functions The -inl.h Files Function Parameter Ordering Names and Order of Includes Scoping Namespaces Nested Classes Nonmember, Static Member, and Global Functions Local Variables Static and Global Variables Classes Doing Work in Constructors Default Constructors Explicit Constructors Copy Constructors Structs vs. Classes Inheritance Multiple Inheritance Interfaces Operator Overloading Access Control Declaration Order Write Short Functions Google-Specific Magic Smart Pointers cpplint Other C++ Features Reference Arguments Function Overloading Default Arguments Variable-Length Arrays and alloca() Friends Exceptions Run-Time Type Information (RTTI) Casting Streams Preincrement and Predecrement Use of const Integer Types 64-bit Portability Preprocessor Macros 0 and NULL sizeof Boost C++0x Naming General Naming Rules File Names Type Names Variable Names Constant Names Function Names Namespace Names Enumerator Names Macro Names Exceptions to Naming Rules Comments Comment Style File Comments Class Comments Function Comments Variable Comments Implementation Comments Punctuation, Spelling and Grammar TODO Comments Deprecation Comments Formatting Line Length Non-ASCII Characters Spaces vs. Tabs Function Declarations and Definitions Function Calls Conditionals Loops and Switch Statements Pointer and Reference Expressions Boolean Expressions Return Values Variable and Array Initialization Preprocessor Directives Class Format Constructor Initializer Lists Namespace Formatting Horizontal Whitespace Vertical Whitespace Exceptions to the Rules Existing Non-conformant Code Windows Code Important Note Displaying Hidden Details in this Guide link ▶This style guide contains many details that are initially hidden from view. They are marked by the triangle icon, which you see here on your left. Click it now. You should see "Hooray" appear below. Hooray! Now you know you can expand points to get more details. Alternatively, there's an "expand all" at the top of this document. Background C++ is the main development language used by many of Google's open-source projects. As every C++ programmer knows, the language has many powerful features, but this power brings with it complexity, which in turn can make code more bug-prone and harder to read and maintain. The goal of this guide is to manage this complexity by describing in detail the dos and don'ts of writing C++ code. These rules exist to keep the code base manageable while still allowing coders to use C++ language features productively. Style, also known as readability, is what we call the conventions that govern our C++ code. The term Style is a bit of a misnomer, since these conventions cover far more than just source file formatting. One way in which we keep the code base manageable is by enforcing consistency. It is very important that any programmer be able to look at another's code and quickly understand it. Maintaining a uniform style and following conventions means that we can more easily use "pattern-matching" to infer what various symbols are and what invariants are true about them. Creating common, required idioms and patterns makes code much easier to understand. In some cases there might be good arguments for changing certain style rules, but we nonetheless keep things as they are in order to preserve consistency. Another issue this guide addresses is that of C++ feature bloat. C++ is a huge language with many advanced features. In some cases we constrain, or even ban, use of certain features. We do this to keep code simple and to avoid the various common errors and problems that these features can cause. This guide lists these features and explains why their use is restricted. Open-source projects developed by Google conform to the requirements in this guide. Note that this guide is not a C++ tutorial: we assume that the reader is familiar with the language. Header Files In general, every .cc file should have an associated .h file. There are some common exceptions, such as unittests and small .cc files containing just a main() function. Correct use of header files can make a huge difference to the readability, size and performance of your code. The following rules will guide you through the various pitfalls of using header files. The #define Guard link ▶All header files should have #define guards to prevent multiple inclusion. The format of the symbol name should be ___H_. To guarantee uniqueness, they should be based on the full path in a project's source tree. For example, the file foo/src/bar/baz.h in project foo should have the following guard: #ifndef FOO_BAR_BAZ_H_ #define FOO_BAR_BAZ_H_ ... #endif // FOO_BAR_BAZ_H_ Header File Dependencies link ▶Don't use an #include when a forward declaration would suffice. When you include a header file you introduce a dependency that will cause your code to be recompiled whenever the header file changes. If your header file includes other header files, any change to those files will cause any code that includes your header to be recompiled. Therefore, we prefer to minimize includes, particularly includes of header files in other header files. You can significantly minimize the number of header files you need to include in your own header files by using forward declarations. For example, if your header file uses the File class in ways that do not require access to the declaration of the File class, your header file can just forward declare class File; instead of having to #include "file/base/file.h". How can we use a class Foo in a header file without access to its definition? We can declare data members of type Foo* or Foo&. We can declare (but not define) functions with arguments, and/or return values, of type Foo. (One exception is if an argument Foo or const Foo& has a non-explicit, one-argument constructor, in which case we need the full definition to support automatic type conversion.) We can declare static data members of type Foo. This is because static data members are defined outside the class definition. On the other hand, you must include the header file for Foo if your class subclasses Foo or has a data member of type Foo. Sometimes it makes sense to have pointer (or better, scoped_ptr) members instead of object members. However, this complicates code readability and imposes a performance penalty, so avoid doing this transformation if the only purpose is to minimize includes in header files. Of course, .cc files typically do require the definitions of the classes they use, and usually have to include several header files. Note: If you use a symbol Foo in your source file, you should bring in a definition for Foo yourself, either via an #include or via a forward declaration. Do not depend on the symbol being brought in transitively via headers not directly included. One exception is if Foo is used in myfile.cc, it's ok to #include (or forward-declare) Foo in myfile.h, instead of myfile.cc. Inline Functions link ▶Define functions inline only when they are small, say, 10 lines or less. Definition: You can declare functions in a way that allows the compiler to expand them inline rather than calling them through the usual function call mechanism. Pros: Inlining a function can generate more efficient object code, as long as the inlined function is small. Feel free to inline accessors and mutators, and other short, performance-critical functions. Cons: Overuse of inlining can actually make programs slower. Depending on a function's size, inlining it can cause the code size to increase or decrease. Inlining a very small accessor function will usually decrease code size while inlining a very large function can dramatically increase code size. On modern processors smaller code usually runs faster due to better use of the instruction cache. Decision: A decent rule of thumb is to not inline a function if it is more than 10 lines long. Beware of destructors, which are often longer than they appear because of implicit member- and base-destructor calls! Another useful rule of thumb: it's typically not cost effective to inline functions with loops or switch statements (unless, in the common case, the loop or switch statement is never executed). It is important to know that functions are not always inlined even if they are declared as such; for example, virtual and recursive functions are not normally inlined. Usually recursive functions should not be inline. The main reason for making a virtual function inline is to place its definition in the class, either for convenience or to document its behavior, e.g., for accessors and mutators. The -inl.h Files link ▶You may use file names with a -inl.h suffix to define complex inline functions when needed. The definition of an inline function needs to be in a header file, so that the compiler has the definition available for inlining at the call sites. However, implementation code properly belongs in .cc files, and we do not like to have much actual code in .h files unless there is a readability or performance advantage. If an inline function definition is short, with very little, if any, logic in it, you should put the code in your .h file. For example, accessors and mutators should certainly be inside a class definition. More complex inline functions may also be put in a .h file for the convenience of the implementer and callers, though if this makes the .h file too unwieldy you can instead put that code in a separate -inl.h file. This separates the implementation from the class definition, while still allowing the implementation to be included where necessary. Another use of -inl.h files is for definitions of function templates. This can be used to keep your template definitions easy to read. Do not forget that a -inl.h file requires a #define guard just like any other header file. Function Parameter Ordering link ▶When defining a function, parameter order is: inputs, then outputs. Parameters to C/C++ functions are either input to the function, output from the function, or both. Input parameters are usually values or const references, while output and input/output parameters will be non-const pointers. When ordering function parameters, put all input-only parameters before any output parameters. In particular, do not add new parameters to the end of the function just because they are new; place new input-only parameters before the output parameters. This is not a hard-and-fast rule. Parameters that are both input and output (often classes/structs) muddy the waters, and, as always, consistency with related functions may require you to bend the rule. Names and Order of Includes link ▶Use standard order for readability and to avoid hidden dependencies: C library, C++ library, other libraries' .h, your project's .h. All of a project's header files should be listed as descentants of the project's source directory without use of UNIX directory shortcuts . (the current directory) or .. (the parent directory). For example, google-awesome-project/src/base/logging.h should be included as #include "base/logging.h" In dir/foo.cc, whose main purpose is to implement or test the stuff in dir2/foo2.h, order your includes as follows: dir2/foo2.h (preferred location — see details below). C system files. C++ system files. Other libraries' .h files. Your project's .h files. The preferred ordering reduces hidden dependencies. We want every header file to be compilable on its own. The easiest way to achieve this is to make sure that every one of them is the first .h file #included in some .cc. dir/foo.cc and dir2/foo2.h are often in the same directory (e.g. base/basictypes_test.cc and base/basictypes.h), but can be in different directories too. Within each section it is nice to order the includes alphabetically. For example, the includes in google-awesome-project/src/foo/internal/fooserver.cc might look like this: #include "foo/public/fooserver.h" // Preferred location. #include #include #include #include #include "base/basictypes.h" #include "base/commandlineflags.h" #include "foo/public/bar.h" Scoping Namespaces link ▶Unnamed namespaces in .cc files are encouraged. With named namespaces, choose the name based on the project, and possibly its path. Do not use a using-directive. Definition: Namespaces subdivide the global scope into distinct, named scopes, and so are useful for preventing name collisions in the global scope. Pros: Namespaces provide a (hierarchical) axis of naming, in addition to the (also hierarchical) name axis provided by classes. For example, if two different projects have a class Foo in the global scope, these symbols may collide at compile time or at runtime. If each project places their code in a namespace, project1::Foo and project2::Foo are now distinct symbols that do not collide. Cons: Namespaces can be confusing, because they provide an additional (hierarchical) axis of naming, in addition to the (also hierarchical) name axis provided by classes. Use of unnamed spaces in header files can easily cause violations of the C++ One Definition Rule (ODR). Decision: Use namespaces according to the policy described below. Unnamed Namespaces Unnamed namespaces are allowed and even encouraged in .cc files, to avoid runtime naming conflicts: namespace { // This is in a .cc file. // The content of a namespace is not indented enum { kUnused, kEOF, kError }; // Commonly used tokens. bool AtEof() { return pos_ == kEOF; } // Uses our namespace's EOF. } // namespace However, file-scope declarations that are associated with a particular class may be declared in that class as types, static data members or static member functions rather than as members of an unnamed namespace. Terminate the unnamed namespace as shown, with a comment // namespace. Do not use unnamed namespaces in .h files. Named Namespaces Named namespaces should be used as follows: Namespaces wrap the entire source file after includes, gflags definitions/declarations, and forward declarations of classes from other namespaces: // In the .h file namespace mynamespace { // All declarations are within the namespace scope. // Notice the lack of indentation. class MyClass { public: ... void Foo(); }; } // namespace mynamespace // In the .cc file namespace mynamespace { // Definition of functions is within scope of the namespace. void MyClass::Foo() { ... } } // namespace mynamespace The typical .cc file might have more complex detail, including the need to reference classes in other namespaces. #include "a.h" DEFINE_bool(someflag, false, "dummy flag"); class C; // Forward declaration of class C in the global namespace. namespace a { class A; } // Forward declaration of a::A. namespace b { ...code for b... // Code goes against the left margin. } // namespace b Do not declare anything in namespace std, not even forward declarations of standard library classes. Declaring entities in namespace std is undefined behavior, i.e., not portable. To declare entities from the standard library, include the appropriate header file. You may not use a using-directive to make all names from a namespace available. // Forbidden -- This pollutes the namespace. using namespace foo; You may use a using-declaration anywhere in a .cc file, and in functions, methods or classes in .h files. // OK in .cc files. // Must be in a function, method or class in .h files. using ::foo::bar; Namespace aliases are allowed anywhere in a .cc file, anywhere inside the named namespace that wraps an entire .h file, and in functions and methods. // Shorten access to some commonly used names in .cc files. namespace fbz = ::foo::bar::baz; // Shorten access to some commonly used names (in a .h file). namespace librarian { // The following alias is available to all files including // this header (in namespace librarian): // alias names should therefore be chosen consistently // within a project. namespace pd_s = ::pipeline_diagnostics::sidetable; inline void my_inline_function() { // namespace alias local to a function (or method). namespace fbz = ::foo::bar::baz; ... } } // namespace librarian Note that an alias in a .h file is visible to everyone #including that file, so public headers (those available outside a project) and headers transitively #included by them, should avoid defining aliases, as part of the general goal of keeping public APIs as small as possible. Nested Classes link ▶Although you may use public nested classes when they are part of an interface, consider a namespace to keep declarations out of the global scope. Definition: A class can define another class within it; this is also called a member class. class Foo { private: // Bar is a member class, nested within Foo. class Bar { ... }; }; Pros: This is useful when the nested (or member) class is only used by the enclosing class; making it a member puts it in the enclosing class scope rather than polluting the outer scope with the class name. Nested classes can be forward declared within the enclosing class and then defined in the .cc file to avoid including the nested class definition in the enclosing class declaration, since the nested class definition is usually only relevant to the implementation. Cons: Nested classes can be forward-declared only within the definition of the enclosing class. Thus, any header file manipulating a Foo::Bar* pointer will have to include the full class declaration for Foo. Decision: Do not make nested classes public unless they are actually part of the interface, e.g., a class that holds a set of options for some method. Nonmember, Static Member, and Global Functions link ▶Prefer nonmember functions within a namespace or static member functions to global functions; use completely global functions rarely. Pros: Nonmember and static member functions can be useful in some situations. Putting nonmember functions in a namespace avoids polluting the global namespace. Cons: Nonmember and static member functions may make more sense as members of a new class, especially if they access external resources or have significant dependencies. Decision: Sometimes it is useful, or even necessary, to define a function not bound to a class instance. Such a function can be either a static member or a nonmember function. Nonmember functions should not depend on external variables, and should nearly always exist in a namespace. Rather than creating classes only to group static member functions which do not share static data, use namespaces instead. Functions defined in the same compilation unit as production classes may introduce unnecessary coupling and link-time dependencies when directly called from other compilation units; static member functions are particularly susceptible to this. Consider extracting a new class, or placing the functions in a namespace possibly in a separate library. If you must define a nonmember function and it is only needed in its .cc file, use an unnamed namespace or static linkage (eg static int Foo() {...}) to limit its scope. Local Variables link ▶Place a function's variables in the narrowest scope possible, and initialize variables in the declaration. C++ allows you to declare variables anywhere in a function. We encourage you to declare them in as local a scope as possible, and as close to the first use as possible. This makes it easier for the reader to find the declaration and see what type the variable is and what it was initialized to. In particular, initialization should be used instead of declaration and assignment, e.g. int i; i = f(); // Bad -- initialization separate from declaration. int j = g(); // Good -- declaration has initialization. Note that gcc implements for (int i = 0; i < 10; ++i) correctly (the scope of i is only the scope of the for loop), so you can then reuse i in another for loop in the same scope. It also correctly scopes declarations in if and while statements, e.g. while (const char* p = strchr(str, '/')) str = p + 1; There is one caveat: if the variable is an object, its constructor is invoked every time it enters scope and is created, and its destructor is invoked every time it goes out of scope. // Inefficient implementation: for (int i = 0; i < 1000000; ++i) { Foo f; // My ctor and dtor get called 1000000 times each. f.DoSomething(i); } It may be more efficient to declare such a variable used in a loop outside that loop: Foo f; // My ctor and dtor get called once each. for (int i = 0; i < 1000000; ++i) { f.DoSomething(i); } Static and Global Variables link ▶Static or global variables of class type are forbidden: they cause hard-to-find bugs due to indeterminate order of construction and destruction. Objects with static storage duration, including global variables, static variables, static class member variables, and function static variables, must be Plain Old Data (POD): only ints, chars, floats, or pointers, or arrays/structs of POD. The order in which class constructors and initializers for static variables are called is only partially specified in C++ and can even change from build to build, which can cause bugs that are difficult to find. Therefore in addition to banning globals of class type, we do not allow static POD variables to be initialized with the result of a function, unless that function (such as getenv(), or getpid()) does not itself depend on any other globals. Likewise, the order in which destructors are called is defined to be the reverse of the order in which the constructors were called. Since constructor order is indeterminate, so is destructor order. For example, at program-end time a static variable might have been destroyed, but code still running -- perhaps in another thread -- tries to access it and fails. Or the destructor for a static 'string' variable might be run prior to the destructor for another variable that contains a reference to that string. As a result we only allow static variables to contain POD data. This rule completely disallows vector (use C arrays instead), or string (use const char []). If you need a static or global variable of a class type, consider initializing a pointer (which will never be freed), from either your main() function or from pthread_once(). Note that this must be a raw pointer, not a "smart" pointer, since the smart pointer's destructor will have the order-of-destructor issue that we are trying to avoid. Classes Classes are the fundamental unit of code in C++. Naturally, we use them extensively. This section lists the main dos and don'ts you should follow when writing a class. Doing Work in Constructors link ▶In general, constructors should merely set member variables to their initial values. Any complex initialization should go in an explicit Init() method. Definition: It is possible to perform initialization in the body of the constructor. Pros: Convenience in typing. No need to worry about whether the class has been initialized or not. Cons: The problems with doing work in constructors are: There is no easy way for constructors to signal errors, short of using exceptions (which are forbidden). If the work fails, we now have an object whose initialization code failed, so it may be an indeterminate state. If the work calls virtual functions, these calls will not get dispatched to the subclass implementations. Future modification to your class can quietly introduce this problem even if your class is not currently subclassed, causing much confusion. If someone creates a global variable of this type (which is against the rules, but still), the constructor code will be called before main(), possibly breaking some implicit assumptions in the constructor code. For instance, gflags will not yet have been initialized. Decision: If your object requires non-trivial initialization, consider having an explicit Init() method. In particular, constructors should not call virtual functions, attempt to raise errors, access potentially uninitialized global variables, etc. Default Constructors link ▶You must define a default constructor if your class defines member variables and has no other constructors. Otherwise the compiler will do it for you, badly. Definition: The default constructor is called when we new a class object with no arguments. It is always called when calling new[] (for arrays). Pros: Initializing structures by default, to hold "impossible" values, makes debugging much easier. Cons: Extra work for you, the code writer. Decision: If your class defines member variables and has no other constructors you must define a default constructor (one that takes no arguments). It should preferably initialize the object in such a way that its internal state is consistent and valid. The reason for this is that if you have no other constructors and do not define a default constructor, the compiler will generate one for you. This compiler generated constructor may not initialize your object sensibly. If your class inherits from an existing class but you add no new member variables, you are not required to have a default constructor. Explicit Constructors link ▶Use the C++ keyword explicit for constructors with one argument. Definition: Normally, if a constructor takes one argument, it can be used as a conversion. For instance, if you define Foo::Foo(string name) and then pass a string to a function that expects a Foo, the constructor will be called to convert the string into a Foo and will pass the Foo to your function for you. This can be convenient but is also a source of trouble when things get converted and new objects created without you meaning them to. Declaring a constructor explicit prevents it from being invoked implicitly as a conversion. Pros: Avoids undesirable conversions. Cons: None. Decision: We require all single argument constructors to be explicit. Always put explicit in front of one-argument constructors in the class definition: explicit Foo(string name); The exception is copy constructors, which, in the rare cases when we allow them, should probably not be explicit. Classes that are intended to be transparent wrappers around other classes are also exceptions. Such exceptions should be clearly marked with comments. Copy Constructors link ▶Provide a copy constructor and assignment operator only when necessary. Otherwise, disable them with DISALLOW_COPY_AND_ASSIGN. Definition: The copy constructor and assignment operator are used to create copies of objects. The copy constructor is implicitly invoked by the compiler in some situations, e.g. passing objects by value. Pros: Copy constructors make it easy to copy objects. STL containers require that all contents be copyable and assignable. Copy constructors can be more efficient than CopyFrom()-style workarounds because they combine construction with copying, the compiler can elide them in some contexts, and they make it easier to avoid heap allocation. Cons: Implicit copying of objects in C++ is a rich source of bugs and of performance problems. It also reduces readability, as it becomes hard to track which objects are being passed around by value as opposed to by reference, and therefore where changes to an object are reflected. Decision: Few classes need to be copyable. Most should have neither a copy constructor nor an assignment operator. In many situations, a pointer or reference will work just as well as a copied value, with better performance. For example, you can pass function parameters by reference or pointer instead of by value, and you can store pointers rather than objects in an STL container. If your class needs to be copyable, prefer providing a copy method, such as CopyFrom() or Clone(), rather than a copy constructor, because such methods cannot be invoked implicitly. If a copy method is insufficient in your situation (e.g. for performance reasons, or because your class needs to be stored by value in an STL container), provide both a copy constructor and assignment operator. If your class does not need a copy constructor or assignment operator, you must explicitly disable them. To do so, add dummy declarations for the copy constructor and assignment operator in the private: section of your class, but do not provide any corresponding definition (so that any attempt to use them results in a link error). For convenience, a DISALLOW_COPY_AND_ASSIGN macro can be used: // 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&) Then, in class Foo: class Foo { public: Foo(int f); ~Foo(); private: DISALLOW_COPY_AND_ASSIGN(Foo); }; Structs vs. Classes link ▶Use a struct only for passive objects that carry data; everything else is a class. The struct and class keywords behave almost identically in C++. We add our own semantic meanings to each keyword, so you should use the appropriate keyword for the data-type you're defining. structs should be used for passive objects that carry data, and may have associated constants, but lack any functionality other than access/setting the data members. The accessing/setting of fields is done by directly accessing the fields rather than through method invocations. Methods should not provide behavior but should only be used to set up the data members, e.g., constructor, destructor, Initialize(), Reset(), Validate(). If more functionality is required, a class is more appropriate. If in doubt, make it a class. For consistency with STL, you can use struct instead of class for functors and traits. Note that member variables in structs and classes have different naming rules. Inheritance link ▶Composition is often more appropriate than inheritance. When using inheritance, make it public. Definition: When a sub-class inherits from a base class, it includes the definitions of all the data and operations that the parent base class defines. In practice, inheritance is used in two major ways in C++: implementation inheritance, in which actual code is inherited by the child, and interface inheritance, in which only method names are inherited. Pros: Implementation inheritance reduces code size by re-using the base class code as it specializes an existing type. Because inheritance is a compile-time declaration, you and the compiler can understand the operation and detect errors. Interface inheritance can be used to programmatically enforce that a class expose a particular API. Again, the compiler can detect errors, in this case, when a class does not define a necessary method of the API. Cons: For implementation inheritance, because the code implementing a sub-class is spread between the base and the sub-class, it can be more difficult to understand an implementation. The sub-class cannot override functions that are not virtual, so the sub-class cannot change implementation. The base class may also define some data members, so that specifies physical layout of the base class. Decision: All inheritance should be public. If you want to do private inheritance, you should be including an instance of the base class as a member instead. Do not overuse implementation inheritance. Composition is often more appropriate. Try to restrict use of inheritance to the "is-a" case: Bar subclasses Foo if it can reasonably be said that Bar "is a kind of" Foo. Make your destructor virtual if necessary. If your class has virtual methods, its destructor should be virtual. Limit the use of protected to those member functions that might need to be accessed from subclasses. Note that data members should be private. When redefining an inherited virtual function, explicitly declare it virtual in the declaration of the derived class. Rationale: If virtual is omitted, the reader has to check all ancestors of the class in question to determine if the function is virtual or not. Multiple Inheritance link ▶Only very rarely is multiple implementation inheritance actually useful. We allow multiple inheritance only when at most one of the base classes has an implementation; all other base classes must be pure interface classes tagged with the Interface suffix. Definition: Multiple inheritance allows a sub-class to have more than one base class. We distinguish between base classes that are pure interfaces and those that have an implementation. Pros: Multiple implementation inheritance may let you re-use even more code than single inheritance (see Inheritance). Cons: Only very rarely is multiple implementation inheritance actually useful. When multiple implementation inheritance seems like the solution, you can usually find a different, more explicit, and cleaner solution. Decision: Multiple inheritance is allowed only when all superclasses, with the possible exception of the first one, are pure interfaces. In order to ensure that they remain pure interfaces, they must end with the Interface suffix. Note: There is an exception to this rule on Windows. Interfaces link ▶Classes that satisfy certain conditions are allowed, but not required, to end with an Interface suffix. Definition: A class is a pure interface if it meets the following requirements: It has only public pure virtual ("= 0") methods and static methods (but see below for destructor). It may not have non-static data members. It need not have any constructors defined. If a constructor is provided, it must take no arguments and it must be protected. If it is a subclass, it may only be derived from classes that satisfy these conditions and are tagged with the Interface suffix. An interface class can never be directly instantiated because of the pure virtual method(s) it declares. To make sure all implementations of the interface can be destroyed correctly, they must also declare a virtual destructor (in an exception to the first rule, this should not be pure). See Stroustrup, The C++ Programming Language, 3rd edition, section 12.4 for details. Pros: Tagging a class with the Interface suffix lets others know that they must not add implemented methods or non static data members. This is particularly important in the case of multiple inheritance. Additionally, the interface concept is already well-understood by Java programmers. Cons: The Interface suffix lengthens the class name, which can make it harder to read and understand. Also, the interface property may be considered an implementation detail that shouldn't be exposed to clients. Decision: A class may end with Interface only if it meets the above requirements. We do not require the converse, however: classes that meet the above requirements are not required to end with Interface. Operator Overloading link ▶Do not overload operators except in rare, special circumstances. Definition: A class can define that operators such as + and / operate on the class as if it were a built-in type. Pros: Can make code appear more intuitive because a class will behave in the same way as built-in types (such as int). Overloaded operators are more playful names for functions that are less-colorfully named, such as Equals() or Add(). For some template functions to work correctly, you may need to define operators. Cons: While operator overloading can make code more intuitive, it has several drawbacks: It can fool our intuition into thinking that expensive operations are cheap, built-in operations. It is much harder to find the call sites for overloaded operators. Searching for Equals() is much easier than searching for relevant invocations of ==. Some operators work on pointers too, making it easy to introduce bugs. Foo + 4 may do one thing, while &Foo + 4 does something totally different. The compiler does not complain for either of these, making this very hard to debug. Overloading also has surprising ramifications. For instance, if a class overloads unary operator&, it cannot safely be forward-declared. Decision: In general, do not overload operators. The assignment operator (operator=), in particular, is insidious and should be avoided. You can define functions like Equals() and CopyFrom() if you need them. Likewise, avoid the dangerous unary operator& at all costs, if there's any possibility the class might be forward-declared. However, there may be rare cases where you need to overload an operator to interoperate with templates or "standard" C++ classes (such as operator<<(ostream&, const T&) for logging). These are acceptable if fully justified, but you should try to avoid these whenever possible. In particular, do not overload operator== or operator< just so that your class can be used as a key in an STL container; instead, you should create equality and comparison functor types when declaring the container. Some of the STL algorithms do require you to overload operator==, and you may do so in these cases, provided you document why. See also Copy Constructors and Function Overloading. Access Control link ▶Make data members private, and provide access to them through accessor functions as needed (for technical reasons, we allow data members of a test fixture class to be protected when using Google Test). Typically a variable would be called foo_ and the accessor function foo(). You may also want a mutator function set_foo(). Exception: static const data members (typically called kFoo) need not be private. The definitions of accessors are usually inlined in the header file. See also Inheritance and Function Names. Declaration Order link ▶Use the specified order of declarations within a class: public: before private:, methods before data members (variables), etc. Your class definition should start with its public: section, followed by its protected: section and then its private: section. If any of these sections are empty, omit them. Within each section, the declarations generally should be in the following order: Typedefs and Enums Constants (static const data members) Constructors Destructor Methods, including static methods Data Members (except static const data members) Friend declarations should always be in the private section, and the DISALLOW_COPY_AND_ASSIGN macro invocation should be at the end of the private: section. It should be the last thing in the class. See Copy Constructors. Method definitions in the corresponding .cc file should be the same as the declaration order, as much as possible. Do not put large method definitions inline in the class definition. Usually, only trivial or performance-critical, and very short, methods may be defined inline. See Inline Functions for more details. Write Short Functions link ▶Prefer small and focused functions. We recognize that long functions are sometimes appropriate, so no hard limit is placed on functions length. If a function exceeds about 40 lines, think about whether it can be broken up without harming the structure of the program. Even if your long function works perfectly now, someone modifying it in a few months may add new behavior. This could result in bugs that are hard to find. Keeping your functions short and simple makes it easier for other people to read and modify your code. You could find long and complicated functions when working with some code. Do not be intimidated by modifying existing code: if working with such a function proves to be difficult, you find that errors are hard to debug, or you want to use a piece of it in several different contexts, consider breaking up the function into smaller and more manageable pieces. Google-Specific Magic There are various tricks and utilities that we use to make C++ code more robust, and various ways we use C++ that may differ from what you see elsewhere. Smart Pointers link ▶If you actually need pointer semantics, scoped_ptr is great. You should only use std::tr1::shared_ptr under very specific conditions, such as when objects need to be held by STL containers. You should never use auto_ptr. "Smart" pointers are objects that act like pointers but have added semantics. When a scoped_ptr is destroyed, for instance, it deletes the object it's pointing to. shared_ptr is the same way, but implements reference-counting so only the last pointer to an object deletes it. Generally speaking, we prefer that we design code with clear object ownership. The clearest object ownership is obtained by using an object directly as a field or local variable, without using pointers at all. On the other extreme, by their very definition, reference counted pointers are owned by nobody. The problem with this design is that it is easy to create circular references or other strange conditions that cause an object to never be deleted. It is also slow to perform atomic operations every time a value is copied or assigned. Although they are not recommended, reference counted pointers are sometimes the simplest and most elegant way to solve a problem. cpplint link ▶Use cpplint.py to detect style errors. cpplint.py is a tool that reads a source file and identifies many style errors. It is not perfect, and has both false positives and false negatives, but it is still a valuable tool. False positives can be ignored by putting // NOLINT at the end of the line. Some projects have instructions on how to run cpplint.py from their project tools. If the project you are contributing to does not, you can download cpplint.py separately. Other C++ Features Reference Arguments link ▶All parameters passed by reference must be labeled const. Definition: In C, if a function needs to modify a variable, the parameter must use a pointer, eg int foo(int *pval). In C++, the function can alternatively declare a reference parameter: int foo(int &val). Pros: Defining a parameter as reference avoids ugly code like (*pval)++. Necessary for some applications like copy constructors. Makes it clear, unlike with pointers, that NULL is not a possible value. Cons: References can be confusing, as they have value syntax but pointer semantics. Decision: Within function parameter lists all references must be const: void Foo(const string &in, string *out); In fact it is a very strong convention in Google code that input arguments are values or const references while output arguments are pointers. Input parameters may be const pointers, but we never allow non-const reference parameters. One case when you might want an input parameter to be a const pointer is if you want to emphasize that the argument is not copied, so it must exist for the lifetime of the object; it is usually best to document this in comments as well. STL adapters such as bind2nd and mem_fun do not permit reference parameters, so you must declare functions with pointer parameters in these cases, too. Function Overloading link ▶Use overloaded functions (including constructors) only if a reader looking at a call site can get a good idea of what is happening without having to first figure out exactly which overload is being called. Definition: You may write a function that takes a const string& and overload it with another that takes const char*. class MyClass { public: void Analyze(const string &text); void Analyze(const char *text, size_t textlen); }; Pros: Overloading can make code more intuitive by allowing an identically-named function to take different arguments. It may be necessary for templatized code, and it can be convenient for Visitors. Cons: If a function is overloaded by the argument types alone, a reader may have to understand C++'s complex matching rules in order to tell what's going on. Also many people are confused by the semantics of inheritance if a derived class overrides only some of the variants of a function. Decision: If you want to overload a function, consider qualifying the name with some information about the arguments, e.g., AppendString(), AppendInt() rather than just Append(). Default Arguments link ▶We do not allow default function parameters, except in a few uncommon situations explained below. Pros: Often you have a function that uses lots of default values, but occasionally you want to override the defaults. Default parameters allow an easy way to do this without having to define many functions for the rare exceptions. Cons: People often figure out how to use an API by looking at existing code that uses it. Default parameters are more difficult to maintain because copy-and-paste from previous code may not reveal all the parameters. Copy-and-pasting of code segments can cause major problems when the default arguments are not appropriate for the new code. Decision: Except as described below, we require all arguments to be explicitly specified, to force programmers to consider the API and the values they are passing for each argument rather than silently accepting defaults they may not be aware of. One specific exception is when default arguments are used to simulate variable-length argument lists. // Support up to 4 params by using a default empty AlphaNum. string StrCat(const AlphaNum &a, const AlphaNum &b = gEmptyAlphaNum, const AlphaNum &c = gEmptyAlphaNum, const AlphaNum &d = gEmptyAlphaNum); Variable-Length Arrays and alloca() link ▶We do not allow variable-length arrays or alloca(). Pros: Variable-length arrays have natural-looking syntax. Both variable-length arrays and alloca() are very efficient. Cons: Variable-length arrays and alloca are not part of Standard C++. More importantly, they allocate a data-dependent amount of stack space that can trigger difficult-to-find memory overwriting bugs: "It ran fine on my machine, but dies mysteriously in production". Decision: Use a safe allocator instead, such as scoped_ptr/scoped_array. Friends link ▶We allow use of friend classes and functions, within reason. Friends should usually be defined in the same file so that the reader does not have to look in another file to find uses of the private members of a class. A common use of friend is to have a FooBuilder class be a friend of Foo so that it can construct the inner state of Foo correctly, without exposing this state to the world. In some cases it may be useful to make a unittest class a friend of the class it tests. Friends extend, but do not break, the encapsulation boundary of a class. In some cases this is better than making a member public when you want to give only one other class access to it. However, most classes should interact with other classes solely through their public members. Exceptions link ▶We do not use C++ exceptions. Pros: Exceptions allow higher levels of an application to decide how to handle "can't happen" failures in deeply nested functions, without the obscuring and error-prone bookkeeping of error codes. Exceptions are used by most other modern languages. Using them in C++ would make it more consistent with Python, Java, and the C++ that others are familiar with. Some third-party C++ libraries use exceptions, and turning them off internally makes it harder to integrate with those libraries. Exceptions are the only way for a constructor to fail. We can simulate this with a factory function or an Init() method, but these require heap allocation or a new "invalid" state, respectively. Exceptions are really handy in testing frameworks. Cons: When you add a throw statement to an existing function, you must examine all of its transitive callers. Either they must make at least the basic exception safety guarantee, or they must never catch the exception and be happy with the program terminating as a result. For instance, if f() calls g() calls h(), and h throws an exception that f catches, g has to be careful or it may not clean up properly. More generally, exceptions make the control flow of programs difficult to evaluate by looking at code: functions may return in places you don't expect. This causes maintainability and debugging difficulties. You can minimize this cost via some rules on how and where exceptions can be used, but at the cost of more that a developer needs to know and understand. Exception safety requires both RAII and different coding practices. Lots of supporting machinery is needed to make writing correct exception-safe code easy. Further, to avoid requiring readers to understand the entire call graph, exception-safe code must isolate logic that writes to persistent state into a "commit" phase. This will have both benefits and costs (perhaps where you're forced to obfuscate code to isolate the commit). Allowing exceptions would force us to always pay those costs even when they're not worth it. Turning on exceptions adds data to each binary produced, increasing compile time (probably slightly) and possibly increasing address space pressure. The availability of exceptions may encourage developers to throw them when they are not appropriate or recover from them when it's not safe to do so. For example, invalid user input should not cause exceptions to be thrown. We would need to make the style guide even longer to document these restrictions! Decision: On their face, the benefits of using exceptions outweigh the costs, especially in new projects. However, for existing code, the introduction of exceptions has implications on all dependent code. If exceptions can be propagated beyond a new project, it also becomes problematic to integrate the new project into existing exception-free code. Because most existing C++ code at Google is not prepared to deal with exceptions, it is comparatively difficult to adopt new code that generates exceptions. Given that Google's existing code is not exception-tolerant, the costs of using exceptions are somewhat greater than the costs in a new project. The conversion process would be slow and error-prone. We don't believe that the available alternatives to exceptions, such as error codes and assertions, introduce a significant burden. Our advice against using exceptions is not predicated on philosophical or moral grounds, but practical ones. Because we'd like to use our open-source projects at Google and it's difficult to do so if those projects use exceptions, we need to advise against exceptions in Google open-source projects as well. Things would probably be different if we had to do it all over again from scratch. There is an exception to this rule (no pun intended) for Windows code. Run-Time Type Information (RTTI) link ▶We do not use Run Time Type Information (RTTI). Definition: RTTI allows a programmer to query the C++ class of an object at run time. Pros: It is useful in some unittests. For example, it is useful in tests of factory classes where the test has to verify that a newly created object has the expected dynamic type. In rare circumstances, it is useful even outside of tests. Cons: A query of type during run-time typically means a design problem. If you need to know the type of an object at runtime, that is often an indication that you should reconsider the design of your class. Decision: Do not use RTTI, except in unittests. If you find yourself in need of writing code that behaves differently based on the class of an object, consider one of the alternatives to querying the type. Virtual methods are the preferred way of executing different code paths depending on a specific subclass type. This puts the work within the object itself. If the work belongs outside the object and instead in some processing code, consider a double-dispatch solution, such as the Visitor design pattern. This allows a facility outside the object itself to determine the type of class using the built-in type system. If you think you truly cannot use those ideas, you may use RTTI. But think twice about it. :-) Then think twice again. Do not hand-implement an RTTI-like workaround. The arguments against RTTI apply just as much to workarounds like class hierarchies with type tags. Casting link ▶Use C++ casts like static_cast(). Do not use other cast formats like int y = (int)x; or int y = int(x);. Definition: C++ introduced a different cast system from C that distinguishes the types of cast operations. Pros: The problem with C casts is the ambiguity of the operation; sometimes you are doing a conversion (e.g., (int)3.5) and sometimes you are doing a cast (e.g., (int)"hello"); C++ casts avoid this. Additionally C++ casts are more visible when searching for them. Cons: The syntax is nasty. Decision: Do not use C-style casts. Instead, use these C++-style casts. Use static_cast as the equivalent of a C-style cast that does value conversion, or when you need to explicitly up-cast a pointer from a class to its superclass. Use const_cast to remove the const qualifier (see const). Use reinterpret_cast to do unsafe conversions of pointer types to and from integer and other pointer types. Use this only if you know what you are doing and you understand the aliasing issues. Do not use dynamic_cast except in test code. If you need to know type information at runtime in this way outside of a unittest, you probably have a design flaw. Streams link ▶Use streams only for logging. Definition: Streams are a replacement for printf() and scanf(). Pros: With streams, you do not need to know the type of the object you are printing. You do not have problems with format strings not matching the argument list. (Though with gcc, you do not have that problem with printf either.) Streams have automatic constructors and destructors that open and close the relevant files. Cons: Streams make it difficult to do functionality like pread(). Some formatting (particularly the common format string idiom %.*s) is difficult if not impossible to do efficiently using streams without using printf-like hacks. Streams do not support operator reordering (the %1s directive), which is helpful for internationalization. Decision: Do not use streams, except where required by a logging interface. Use printf-like routines instead. There are various pros and cons to using streams, but in this case, as in many other cases, consistency trumps the debate. Do not use streams in your code. Extended Discussion There has been debate on this issue, so this explains the reasoning in greater depth. Recall the Only One Way guiding principle: we want to make sure that whenever we do a certain type of I/O, the code looks the same in all those places. Because of this, we do not want to allow users to decide between using streams or using printf plus Read/Write/etc. Instead, we should settle on one or the other. We made an exception for logging because it is a pretty specialized application, and for historical reasons. Proponents of streams have argued that streams are the obvious choice of the two, but the issue is not actually so clear. For every advantage of streams they point out, there is an equivalent disadvantage. The biggest advantage is that you do not need to know the type of the object to be printing. This is a fair point. But, there is a downside: you can easily use the wrong type, and the compiler will not warn you. It is easy to make this kind of mistake without knowing when using streams. cout << this; // Prints the address cout << *this; // Prints the contents The compiler does not generate an error because << has been overloaded. We discourage overloading for just this reason. Some say printf formatting is ugly and hard to read, but streams are often no better. Consider the following two fragments, both with the same typo. Which is easier to discover? cerr << "Error connecting to '" hostname.first << ":" hostname.second << ": " hostname.first, foo->bar()->hostname.second, strerror(errno)); And so on and so forth for any issue you might bring up. (You could argue, "Things would be better with the right wrappers," but if it is true for one scheme, is it not also true for the other? Also, remember the goal is to make the language smaller, not add yet more machinery that someone has to learn.) Either path would yield different advantages and disadvantages, and there is not a clearly superior solution. The simplicity doctrine mandates we settle on one of them though, and the majority decision was on printf + read/write. Preincrement and Predecrement link ▶Use prefix form (++i) of the increment and decrement operators with iterators and other template objects. Definition: When a variable is incremented (++i or i++) or decremented (--i or i--) and the value of the expression is not used, one must decide whether to preincrement (decrement) or postincrement (decrement). Pros: When the return value is ignored, the "pre" form (++i) is never less efficient than the "post" form (i++), and is often more efficient. This is because post-increment (or decrement) requires a copy of i to be made, which is the value of the expression. If i is an iterator or other non-scalar type, copying i could be expensive. Since the two types of increment behave the same when the value is ignored, why not just always pre-increment? Cons: The tradition developed, in C, of using post-increment when the expression value is not used, especially in for loops. Some find post-increment easier to read, since the "subject" (i) precedes the "verb" (++), just like in English. Decision: For simple scalar (non-object) values there is no reason to prefer one form and we allow either. For iterators and other template types, use pre-increment. Use of const link ▶We strongly recommend that you use const whenever it makes sense to do so. Definition: Declared variables and parameters can be preceded by the keyword const to indicate the variables are not changed (e.g., const int foo). Class functions can have the const qualifier to indicate the function does not change the state of the class member variables (e.g., class Foo { int Bar(char c) const; };). Pros: Easier for people to understand how variables are being used. Allows the compiler to do better type checking, and, conceivably, generate better code. Helps people convince themselves of program correctness because they know the functions they call are limited in how they can modify your variables. Helps people know what functions are safe to use without locks in multi-threaded programs. Cons: const is viral: if you pass a const variable to a function, that function must have const in its prototype (or the variable will need a const_cast). This can be a particular problem when calling library functions. Decision: const variables, data members, methods and arguments add a level of compile-time type checking; it is better to detect errors as soon as possible. Therefore we strongly recommend that you use const whenever it makes sense to do so: If a function does not modify an argument passed by reference or by pointer, that argument should be const. Declare methods to be const whenever possible. Accessors should almost always be const. Other methods should be const if they do not modify any data members, do not call any non-const methods, and do not return a non-const pointer or non-const reference to a data member. Consider making data members const whenever they do not need to be modified after construction. However, do not go crazy with const. Something like const int * const * const x; is likely overkill, even if it accurately describes how const x is. Focus on what's really useful to know: in this case, const int** x is probably sufficient. The mutable keyword is allowed but is unsafe when used with threads, so thread safety should be carefully considered first. Where to put the const Some people favor the form int const *foo to const int* foo. They argue that this is more readable because it's more consistent: it keeps the rule that const always follows the object it's describing. However, this consistency argument doesn't apply in this case, because the "don't go crazy" dictum eliminates most of the uses you'd have to be consistent with. Putting the const first is arguably more readable, since it follows English in putting the "adjective" (const) before the "noun" (int). That said, while we encourage putting const first, we do not require it. But be consistent with the code around you! Integer Types link ▶Of the built-in C++ integer types, the only one used is int. If a program needs a variable of a different size, use a precise-width integer type from , such as int16_t. Definition: C++ does not specify the sizes of its integer types. Typically people assume that short is 16 bits, int is 32 bits, long is 32 bits and long long is 64 bits. Pros: Uniformity of declaration. Cons: The sizes of integral types in C++ can vary based on compiler and architecture. Decision: defines types like int16_t, uint32_t, int64_t, etc. You should always use those in preference to short, unsigned long long and the like, when you need a guarantee on the size of an integer. Of the C integer types, only int should be used. When appropriate, you are welcome to use standard types like size_t and ptrdiff_t. We use int very often, for integers we know are not going to be too big, e.g., loop counters. Use plain old int for such things. You should assume that an int is at least 32 bits, but don't assume that it has more than 32 bits. If you need a 64-bit integer type, use int64_t or uint64_t. For integers we know can be "big", use int64_t. You should not use the unsigned integer types such as uint32_t, unless the quantity you are representing is really a bit pattern rather than a number, or unless you need defined twos-complement overflow. In particular, do not use unsigned types to say a number will never be negative. Instead, use assertions for this. On Unsigned Integers Some people, including some textbook authors, recommend using unsigned types to represent numbers that are never negative. This is intended as a form of self-documentation. However, in C, the advantages of such documentation are outweighed by the real bugs it can introduce. Consider: for (unsigned int i = foo.Length()-1; i >= 0; --i) ... This code will never terminate! Sometimes gcc will notice this bug and warn you, but often it will not. Equally bad bugs can occur when comparing signed and unsigned variables. Basically, C's type-promotion scheme causes unsigned types to behave differently than one might expect. So, document that a variable is non-negative using assertions. Don't use an unsigned type. 64-bit Portability link ▶Code should be 64-bit and 32-bit friendly. Bear in mind problems of printing, comparisons, and structure alignment. printf() specifiers for some types are not cleanly portable between 32-bit and 64-bit systems. C99 defines some portable format specifiers. Unfortunately, MSVC 7.1 does not understand some of these specifiers and the standard is missing a few, so we have to define our own ugly versions in some cases (in the style of the standard include file inttypes.h): // printf macros for size_t, in the style of inttypes.h #ifdef _LP64 #define __PRIS_PREFIX "z" #else #define __PRIS_PREFIX #endif // Use these macros after a % in a printf format string // to get correct 32/64 bit behavior, like this: // size_t size = records.size(); // printf("%"PRIuS"\n", size); #define PRIdS __PRIS_PREFIX "d" #define PRIxS __PRIS_PREFIX "x" #define PRIuS __PRIS_PREFIX "u" #define PRIXS __PRIS_PREFIX "X" #define PRIoS __PRIS_PREFIX "o" Type DO NOT use DO use Notes void * (or any pointer) %lx %p int64_t %qd, %lld %"PRId64" uint64_t %qu, %llu, %llx %"PRIu64", %"PRIx64" size_t %u %"PRIuS", %"PRIxS" C99 specifies %zu ptrdiff_t %d %"PRIdS" C99 specifies %zd Note that the PRI* macros expand to independent strings which are concatenated by the compiler. Hence if you are using a non-constant format string, you need to insert the value of the macro into the format, rather than the name. It is still possible, as usual, to include length specifiers, etc., after the % when using the PRI* macros. So, e.g. printf("x = %30"PRIuS"\n", x) would expand on 32-bit Linux to printf("x = %30" "u" "\n", x), which the compiler will treat as printf("x = %30u\n", x). Remember that sizeof(void *) != sizeof(int). Use intptr_t if you want a pointer-sized integer. You may need to be careful with structure alignments, particularly for structures being stored on disk. Any class/structure with a int64_t/uint64_t member will by default end up being 8-byte aligned on a 64-bit system. If you have such structures being shared on disk between 32-bit and 64-bit code, you will need to ensure that they are packed the same on both architectures. Most compilers offer a way to alter structure alignment. For gcc, you can use __attribute__((packed)). MSVC offers #pragma pack() and __declspec(align()). Use the LL or ULL suffixes a
C++ 标准 ISO 14882－2011
Contents Contents iii List of Tables xi List of Figures xv 1 General 1 1.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Normative references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Terms and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.4 Implementation compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.5 Structure of this International Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.6 Syntax notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.7 The C++ memory model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.8 The C++ object model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.9 Program execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.10 Multi-threaded executions and data races . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.11 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2 Lexical conventions 17 2.1 Separate translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2 Phases of translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.3 Character sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.4 Trigraph sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.5 Preprocessing tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.6 Alternative tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.7 Tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.8 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.9 Header names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.10 Preprocessing numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.11 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.12 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.13 Operators and punctuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.14 Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3 Basic concepts 34 3.1 Declarations and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.2 One definition rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.4 Name lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.5 Program and linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.6 Start and termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.7 Storage duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.8 Object lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.9 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 3.10 Lvalues and rvalues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Contents iii ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 3.11 Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 4 Standard conversions 81 4.1 Lvalue-to-rvalue conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4.2 Array-to-pointer conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4.3 Function-to-pointer conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4.4 Qualification conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 4.5 Integral promotions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 4.6 Floating point promotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.7 Integral conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.8 Floating point conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.9 Floating-integral conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.10 Pointer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.11 Pointer to member conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.12 Boolean conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 4.13 Integer conversion rank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5 Expressions 87 5.1 Primary expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 5.2 Postfix expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.3 Unary expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 5.4 Explicit type conversion (cast notation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 5.5 Pointer-to-member operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 5.6 Multiplicative operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 5.7 Additive operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 5.8 Shift operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 5.9 Relational operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 5.10 Equality operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 5.11 Bitwise AND operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.12 Bitwise exclusive OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.13 Bitwise inclusive OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.14 Logical AND operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 5.15 Logical OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.16 Conditional operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 5.17 Assignment and compound assignment operators . . . . . . . . . . . . . . . . . . . . . . . . 125 5.18 Comma operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 5.19 Constant expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 6 Statements 130 6.1 Labeled statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 6.2 Expression statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 6.3 Compound statement or block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 6.4 Selection statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 6.5 Iteration statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 6.6 Jump statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 6.7 Declaration statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 6.8 Ambiguity resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 7 Declarations 140 7.1 Specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 7.2 Enumeration declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Contents iv ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 7.3 Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 7.4 The asm declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 7.5 Linkage specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 7.6 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 8 Declarators 182 8.1 Type names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 8.2 Ambiguity resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 8.3 Meaning of declarators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 8.4 Function definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 8.5 Initializers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 9 Classes 216 9.1 Class names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 9.2 Class members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 9.3 Member functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 9.4 Static members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 9.5 Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 9.6 Bit-fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 9.7 Nested class declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 9.8 Local class declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 9.9 Nested type names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 10 Derived classes 233 10.1 Multiple base classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 10.2 Member name lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 10.3 Virtual functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 10.4 Abstract classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 11 Member access control 246 11.1 Access specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 11.2 Accessibility of base classes and base class members . . . . . . . . . . . . . . . . . . . . . . . 249 11.3 Friends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 11.4 Protected member access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 11.5 Access to virtual functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 11.6 Multiple access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 11.7 Nested classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 12 Special member functions 257 12.1 Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 12.2 Temporary objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 12.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 12.4 Destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 12.5 Free store . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 12.6 Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 12.7 Construction and destruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 12.8 Copying and moving class objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 12.9 Inheriting constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 13 Overloading 289 13.1 Overloadable declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Contents v ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 13.2 Declaration matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 13.3 Overload resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 13.4 Address of overloaded function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 13.5 Overloaded operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313 13.6 Built-in operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317 14 Templates 321 14.1 Template parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 14.2 Names of template specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325 14.3 Template arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 14.4 Type equivalence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 14.5 Template declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 14.6 Name resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 14.7 Template instantiation and specialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366 14.8 Function template specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 15 Exception handling 400 15.1 Throwing an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 15.2 Constructors and destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 15.3 Handling an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 15.4 Exception specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 15.5 Special functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 16 Preprocessing directives 411 16.1 Conditional inclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 16.2 Source file inclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 16.3 Macro replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 16.4 Line control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420 16.5 Error directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 16.6 Pragma directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 16.7 Null directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 16.8 Predefined macro names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 16.9 Pragma operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423 17 Library introduction 424 17.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 17.2 The C standard library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 17.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 17.4 Additional definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 17.5 Method of description (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428 17.6 Library-wide requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434 18 Language support library 454 18.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454 18.2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454 18.3 Implementation properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455 18.4 Integer types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 18.5 Start and termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 18.6 Dynamic memory management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467 18.7 Type identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473 18.8 Exception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475 Contents vi ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 18.9 Initializer lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 480 18.10 Other runtime support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 19 Diagnostics library 484 19.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 19.2 Exception classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 19.3 Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 19.4 Error numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 19.5 System error support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 20 General utilities library 500 20.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 20.2 Utility components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 20.3 Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 20.4 Tuples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 20.5 Class template bitset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518 20.6 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525 20.7 Smart pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 20.8 Function objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 566 20.9 Metaprogramming and type traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585 20.10 Compile-time rational arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 602 20.11 Time utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 20.12 Class template scoped_allocator_adaptor . . . . . . . . . . . . . . . . . . . . . . . . . . . 620 20.13 Class type_index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625 21 Strings library 628 21.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628 21.2 Character traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628 21.3 String classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 634 21.4 Class template basic_string . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 638 21.5 Numeric conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665 21.6 Hash support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666 21.7 Null-terminated sequence utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667 22 Localization library 671 22.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671 22.2 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671 22.3 Locales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 672 22.4 Standard locale categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684 22.5 Standard code conversion facets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725 22.6 C library locales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 23 Containers library 728 23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728 23.2 Container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728 23.3 Sequence containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754 23.4 Associative containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786 23.5 Unordered associative containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803 23.6 Container adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 819 24 Iterators library 829 Contents vii ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 24.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 24.2 Iterator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 24.3 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 24.4 Iterator primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837 24.5 Iterator adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841 24.6 Stream iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855 25 Algorithms library 863 25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863 25.2 Non-modifying sequence operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873 25.3 Mutating sequence operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 878 25.4 Sorting and related operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 887 25.5 C library algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900 26 Numerics library 902 26.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902 26.2 Numeric type requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902 26.3 The floating-point environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903 26.4 Complex numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904 26.5 Random number generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914 26.6 Numeric arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 959 26.7 Generalized numeric operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 981 26.8 C library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984 27 Input/output library 989 27.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989 27.2 Iostreams requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990 27.3 Forward declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 990 27.4 Standard iostream objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 992 27.5 Iostreams base classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 994 27.6 Stream buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1013 27.7 Formatting and manipulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1023 27.8 String-based streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049 27.9 File-based streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1061 28 Regular expressions library 1076 28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076 28.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076 28.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1077 28.4 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1079 28.5 Namespace std::regex_constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1086 28.6 Class regex_error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089 28.7 Class template regex_traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089 28.8 Class template basic_regex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1092 28.9 Class template sub_match . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1097 28.10 Class template match_results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1103 28.11 Regular expression algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1108 28.12 Regular expression iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1113 28.13 Modified ECMAScript regular expression grammar . . . . . . . . . . . . . . . . . . . . . . . 1119 29 Atomic operations library 1122 Contents viii ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 29.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122 29.2 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122 29.3 Order and consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1125 29.4 Lock-free property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1128 29.5 Atomic types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1128 29.6 Operations on atomic types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132 29.7 Flag type and operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1137 29.8 Fences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1138 30 Thread support library 1140 30.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140 30.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140 30.3 Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1143 30.4 Mutual exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1149 30.5 Condition variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162 30.6 Futures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170 A Grammar summary 1187 A.1 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1187 A.2 Lexical conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1187 A.3 Basic concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1192 A.4 Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1192 A.5 Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1195 A.6 Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1196 A.7 Declarators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1200 A.8 Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1202 A.9 Derived classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203 A.10 Special member functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1203 A.11 Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204 A.12 Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204 A.13 Exception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205 A.14 Preprocessing directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1205 B Implementation quantities 1207 C Compatibility 1209 C.1 C++ and ISO C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1209 C.2 C++ and ISO C++ 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1218 C.3 C standard library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225 D Compatibility features 1229 D.1 Increment operator with bool operand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 D.2 register keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 D.3 Implicit declaration of copy functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 D.4 Dynamic exception specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 D.5 C standard library headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 D.6 Old iostreams members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1230 D.7 char* streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231 D.8 Function objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1240 D.9 Binders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1243 D.10 auto_ptr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1245 Contents ix ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved D.11 Violating exception-specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1247 E Universal character names for identifier characters 1249 E.1 Ranges of characters allowed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1249 E.2 Ranges of characters disallowed initially . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1249 F Cross references 1250 Index 1268 Index of grammar productions 1297 Index of library names 1300 Index of implementation-defined behavior 1336 Contents x ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved List of Tables 1 Trigraph sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2 Alternative tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3 Identifiers with special meaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5 Alternative representations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6 Types of integer constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7 Escape sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8 String literal concatenations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9 Relations on const and volatile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 10 simple-type-specifiers and the types they specify . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11 Relationship between operator and function call notation . . . . . . . . . . . . . . . . . . . . . . 297 12 Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 13 Library categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424 14 C++ library headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 15 C++ headers for C library facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 16 C++ headers for freestanding implementations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436 17 EqualityComparable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 18 LessThanComparable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 19 DefaultConstructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 20 MoveConstructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 21 CopyConstructible requirements (in addition to MoveConstructible) . . . . . . . . . . . . . . . 438 22 MoveAssignable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 23 CopyAssignable requirements(in addition to MoveAssignable) . . . . . . . . . . . . . . . . . . . 438 24 Destructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 25 NullablePointer requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440 26 Hash requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 27 Descriptive variable definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441 28 Allocator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 442 29 Language support library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454 30 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454 31 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 32 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 33 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466 34 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 35 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 36 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 37 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 38 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 39 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 40 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 List of Tables xi ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 41 Diagnostics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484 42 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 488 43 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489 44 General utilities library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 45 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 46 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540 47 Primary type category predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 48 Composite type category predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 49 Type property predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 590 50 Type property queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595 51 Type relationship predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596 52 Const-volatile modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 53 Reference modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 54 Sign modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 55 Array modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 56 Pointer modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 599 57 Other transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 58 Expressions used to perform ratio arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604 59 Clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608 60 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 619 61 Strings library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628 62 Character traits requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629 63 basic_string(const Allocator&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 64 basic_string(const basic_string&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 65 basic_string(const basic_string&, size_type, size_type, const Allocator&) effects . 643 66 basic_string(const charT*, size_type, const Allocator&) effects . . . . . . . . . . . . . . 644 67 basic_string(const charT*, const Allocator&) effects . . . . . . . . . . . . . . . . . . . . . 644 68 basic_string(size_t, charT, const Allocator&) effects . . . . . . . . . . . . . . . . . . . . 644 69 basic_string(const basic_string&, const Allocator&) and basic_string(basic_string&&, const Allocator&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645 70 operator=(const basic_string&) effects . . . . . . . . . . . . . 645 71 operator=(const basic_string&&) effects . . . . . . . . . . . . 645 72 compare() results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659 73 Potential mbstate_t data races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668 74 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668 75 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669 76 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669 77 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669 78 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 669 79 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 670 80 Localization library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671 81 Locale category facets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675 82 Required specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676 83 do_in/do_out result values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694 84 do_unshift result values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694 85 Integer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 86 Length modifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 87 Integer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 List of Tables xii ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 88 Floating-point conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703 89 Length modifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703 90 Numeric conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703 91 Fill padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704 92 do_get_date effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711 93 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 94 Potential setlocale data races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 727 95 Containers library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 728 96 Container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 729 97 Reversible container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 731 98 Optional container operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732 99 Allocator-aware container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 733 100 Sequence container requirements (in addition to container) . . . . . . . . . . . . . . . . . . . . . 735 101 Optional sequence container operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 737 102 Associative container requirements (in addition to container) . . . . . . . . . . . . . . . . . . . . 740 103 Unordered associative container requirements (in addition to container) . . . . . . . . . . . . . . 746 104 Iterators library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 105 Relations among iterator categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 106 Iterator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 107 Input iterator requirements (in addition to Iterator) . . . . . . . . . . . . . . . . . . . . . . . . . 831 108 Output iterator requirements (in addition to Iterator) . . . . . . . . . . . . . . . . . . . . . . . . 832 109 Forward iterator requirements (in addition to input iterator) . . . . . . . . . . . . . . . . . . . . 833 110 Bidirectional iterator requirements (in addition to forward iterator) . . . . . . . . . . . . . . . . . 833 111 Random access iterator requirements (in addition to bidirectional iterator) . . . . . . . . . . . . 834 112 Algorithms library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 863 113 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900 114 Numerics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902 115 Seed sequence requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915 116 Uniform random number generator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 916 117 Random number engine requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 917 118 Random number distribution requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921 119 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 984 120 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 985 121 Input/output library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989 122 fmtflags effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 999 123 fmtflags constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 999 124 iostate effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 999 125 openmode effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000 126 seekdir effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000 127 Position type requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004 128 basic_ios::init() effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1007 129 basic_ios::copyfmt() effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1008 130 seekoff positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054 131 newoff values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054 132 File open modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064 133 seekoff effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1067 List of Tables xiii ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved 134 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1074 135 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1075 136 Regular expressions library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1076 137 Regular expression traits class requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1077 138 syntax_option_type effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 139 regex_constants::match_flag_type effects when obtaining a match against a character container sequence [first,last). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 140 error_type values in the C locale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088 141 match_results assignment operator effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1105 142 Effects of regex_match algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1109 143 Effects of regex_search algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1110 144 Atomics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1122 145 atomic integral typedefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1131 146 atomic typedefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1132 147 Atomic arithmetic computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1136 148 Thread support library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1140 149 Standard macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225 150 Standard values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225 151 Standard types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226 152 Standard structs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226 153 Standard functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1226 154 C headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 155 strstreambuf(streamsize) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1233 156 strstreambuf(void* (*)(size_t), void (*)(void*)) effects . . . . . . . . . . . . . . . . . . 1233 157 strstreambuf(charT*, streamsize, charT*) effects . . . . . . . . . . . . . . . . . . . . . . . . 1234 158 seekoff positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236 159 newoff values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1236 List of Tables xiv ISO/IEC 14882:2011(E) © ISO/IEC 2011 – All rights reserved List of Figures 1 Expression category taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 2 Directed acyclic graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 3 Non-virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 4 Virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 5 Virtual and non-virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 6 Name lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 7 Stream position, offset, and size types [non-normative] . . . . . . . . . . . . . . . . . . . . . . . . 989 List of
Go语言官方文档学习笔记（第三季）
Go富有表现力，简洁，整洁且高效。它的并发机制使编写程序可以轻松地从多核和联网机器中获得最大收益，而其新颖的类型系统则可以实现灵活的模块化程序构造。Go可以快速编译为机器代码，但具有垃圾回收的便利性和运行时反射的功能。它是一种快速的，静态类型的编译语言，感觉就像是一种动态类型的解释语言。Go语言官方文档学习笔记是基于官方文档及个人学习Go的笔记，整理完成的Go语言快速入门课程。 第三季内容包括以下十个部分：1-Short variable declarations2-Basic types3-Zero values4-Type conversions5-Type inference6-Constants7-Numeric Constants8-For9-For continued10-For is Go's while
Google C++ International Standard.pdf
Contents Contents ii List of Tables x List of Figures xiv 1 Scope 1 2 Normative references 2 3 Terms and definitions 3 4 General principles 7 4.1 Implementation compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2 Structure of this document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.3 Syntax notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4 The C++ memory model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.5 The C++ object model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.6 Program execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.7 Multi-threaded executions and data races . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.8 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5 Lexical conventions 22 5.1 Separate translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.2 Phases of translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.3 Character sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.4 Preprocessing tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.5 Alternative tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.6 Tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.7 Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.8 Header names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.9 Preprocessing numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5.10 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 5.11 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5.12 Operators and punctuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.13 Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6 Basic concepts 39 6.1 Declarations and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 6.2 One-definition rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 6.3 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 6.4 Name lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 6.5 Program and linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6.6 Start and termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 6.7 Storage duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 6.8 Object lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Contents ii ©ISO/IEC N4659 6.9 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.10 Lvalues and rvalues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.11 Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 7 Standard conversions 86 7.1 Lvalue-to-rvalue conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 7.2 Array-to-pointer conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 7.3 Function-to-pointer conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.4 Temporary materialization conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.5 Qualification conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.6 Integral promotions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.7 Floating-point promotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.8 Integral conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.9 Floating-point conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.10 Floating-integral conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.11 Pointer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.12 Pointer to member conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 7.13 Function pointer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.14 Boolean conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.15 Integer conversion rank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 8 Expressions 93 8.1 Primary expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 8.2 Postfix expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 8.3 Unary expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 8.4 Explicit type conversion (cast notation) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 8.5 Pointer-to-member operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 8.6 Multiplicative operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 8.7 Additive operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 8.8 Shift operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 8.9 Relational operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 8.10 Equality operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 8.11 Bitwise AND operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.12 Bitwise exclusive OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.13 Bitwise inclusive OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.14 Logical AND operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.15 Logical OR operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 8.16 Conditional operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 8.17 Throwing an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 8.18 Assignment and compound assignment operators . . . . . . . . . . . . . . . . . . . . . . . 138 8.19 Comma operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 8.20 Constant expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 9 Statements 144 9.1 Labeled statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 9.2 Expression statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 9.3 Compound statement or block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 9.4 Selection statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 9.5 Iteration statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 9.6 Jump statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 9.7 Declaration statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Contents iii ©ISO/IEC N4659 9.8 Ambiguity resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 10 Declarations 155 10.1 Specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 10.2 Enumeration declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 10.3 Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 10.4 The asm declaration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 10.5 Linkage specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 10.6 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 11 Declarators 201 11.1 Type names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 11.2 Ambiguity resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 11.3 Meaning of declarators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 11.4 Function definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 11.5 Structured binding declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 11.6 Initializers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 12 Classes 237 12.1 Class names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 12.2 Class members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 12.3 Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 12.4 Local class declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 13 Derived classes 256 13.1 Multiple base classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 13.2 Member name lookup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 13.3 Virtual functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 13.4 Abstract classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 14 Member access control 269 14.1 Access specifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 14.2 Accessibility of base classes and base class members . . . . . . . . . . . . . . . . . . . . . . 271 14.3 Friends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 14.4 Protected member access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 14.5 Access to virtual functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 14.6 Multiple access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 14.7 Nested classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 15 Special member functions 280 15.1 Constructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 15.2 Temporary objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 15.3 Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 15.4 Destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 15.5 Free store . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 15.6 Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 15.7 Construction and destruction . . . . . . . . . . . . . . . . . . . . . . . . ©ISO/IEC N4659 16.3 Overload resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314 16.4 Address of overloaded function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 16.5 Overloaded operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 16.6 Built-in operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 17 Templates 344 17.1 Template parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 17.2 Names of template specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 17.3 Template arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350 17.4 Type equivalence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 17.5 Template declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 17.6 Name resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 17.7 Template instantiation and specialization . . . . . . . . . . . . . . . . . . . . . . . . . . . 390 17.8 Function template specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402 17.9 Deduction guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423 18 Exception handling 424 18.1 Throwing an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425 18.2 Constructors and destructors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 18.3 Handling an exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 18.4 Exception specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429 18.5 Special functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432 19 Preprocessing directives 434 19.1 Conditional inclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435 19.2 Source file inclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 19.3 Macro replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438 19.4 Line control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 19.5 Error directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 19.6 Pragma directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 19.7 Null directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 19.8 Predefined macro names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 19.9 Pragma operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 20 Library introduction 447 20.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 20.2 The C standard library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 20.3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 20.4 Method of description (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451 20.5 Library-wide requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 21 Language support library 478 21.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 21.2 Common definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 21.3 Implementation properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 21.4 Integer types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 492 21.5 Start and termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493 21.6 Dynamic memory management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494 21.7 Type identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502 21.8 Exception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 21.9 Initializer lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 509 Contents v ©ISO/IEC N4659 21.10 Other runtime support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 22 Diagnostics library 513 22.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 22.2 Exception classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 22.3 Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 22.4 Error numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 22.5 System error support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 519 23 General utilities library 530 23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530 23.2 Utility components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530 23.3 Compile-time integer sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 538 23.4 Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 23.5 Tuples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543 23.6 Optional objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554 23.7 Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569 23.8 Storage for any type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 582 23.9 Bitsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 587 23.10 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 23.11 Smart pointers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609 23.12 Memory resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 635 23.13 Class template scoped_allocator_adaptor . . . . . . . . . . . . . . . . . . . . . . . . . . 646 23.14 Function objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652 23.15 Metaprogramming and type traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 676 23.16 Compile-time rational arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 702 23.17 Time utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 705 23.18 Class type_index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 722 23.19 Execution policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 723 24 Strings library 726 24.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 24.2 Character traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 24.3 String classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732 24.4 String view classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 766 24.5 Null-terminated sequence utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 776 25 Localization library 782 25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782 25.2 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782 25.3 Locales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784 25.4 Standard locale categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791 25.5 C library locales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 26 Containers library 830 26.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 26.2 Container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 26.3 Sequence containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868 26.4 Associative containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900 26.5 Unordered associative containers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 921 26.6 Container adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 945 Contents vi ©ISO/IEC N4659 27 Iterators library 955 27.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955 27.2 Iterator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955 27.3 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961 27.4 Iterator primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 964 27.5 Iterator adaptors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 967 27.6 Stream iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 980 27.7 Range access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 987 27.8 Container access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 988 28 Algorithms library 989 28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989 28.2 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989 28.3 Algorithms requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1008 28.4 Parallel algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1009 28.5 Non-modifying sequence operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1012 28.6 Mutating sequence operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1020 28.7 Sorting and related operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1030 28.8 C library algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049 29 Numerics library 1050 29.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050 29.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050 29.3 Numeric type requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050 29.4 The floating-point environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051 29.5 Complex numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052 29.6 Random number generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1062 29.7 Numeric arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1105 29.8 Generalized numeric operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1125 29.9 Mathematical functions for floating-point types . . . . . . . . . . . . . . . . . . . . . . . . 1139 30 Input/output library 1157 30.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1157 30.2 Iostreams requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1158 30.3 Forward declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1158 30.4 Standard iostream objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1160 30.5 Iostreams base classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1162 30.6 Stream buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1179 30.7 Formatting and manipulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1188 30.8 String-based streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1214 30.9 File-based streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1225 30.10 File systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1239 30.11 C library files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1293 31 Regular expressions library 1297 31.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297 31.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297 31.3 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298 31.4 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1300 31.5 Namespace std::regex_constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1306 31.6 Class regex_error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1309 Contents vii ©ISO/IEC N4659 31.7 Class template regex_traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1310 31.8 Class template basic_regex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1312 31.9 Class template sub_match . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1318 31.10 Class template match_results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1323 31.11 Regular expression algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1328 31.12 Regular expression iterators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1333 31.13 Modified ECMAScript regular expression grammar . . . . . . . . . . . . . . . . . . . . . . 1339 32 Atomic operations library 1342 32.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342 32.2 Header synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342 32.3 Type aliases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1346 32.4 Order and consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1346 32.5 Lock-free property . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1348 32.6 Class template atomic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1348 32.7 Non-member functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1356 32.8 Flag type and operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1356 32.9 Fences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1357 33 Thread support library 1359 33.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1359 33.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1359 33.3 Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1362 33.4 Mutual exclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1367 33.5 Condition variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1388 33.6 Futures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1395 A Grammar summary 1412 A.1 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1412 A.2 Lexical conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1412 A.3 Basic concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1417 A.4 Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1417 A.5 Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1421 A.6 Declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1422 A.7 Declarators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1426 A.8 Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1428 A.9 Derived classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1429 A.10 Special member functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1430 A.11 Overloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1430 A.12 Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1430 A.13 Exception handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1431 A.14 Preprocessing directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1432 B Implementation quantities 1434 C Compatibility 1436 C.1 C++ and ISO C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1436 C.2 C++ and ISO C++ 2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1445 C.3 C++ and ISO C++ 2011 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1451 C.4 C++ and ISO C++ 2014 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1453 C.5 C standard library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1457 Contents viii ©ISO/IEC N4659 D Compatibility features 1460 D.1 Redeclaration of static constexpr data members . . . . . . . . . . . . . . . . . . . . . . 1460 D.2 Implicit declaration of copy functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1460 D.3 Deprecated exception specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1460 D.4 C++ standard library headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1460 D.5 C standard library headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1461 D.6 char* streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1461 D.7 uncaught_exception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1470 D.8 Old adaptable function bindings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1470 D.9 The default allocator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1475 D.10 Raw storage iterator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1476 D.11 Temporary buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478 D.12 Deprecated type traits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1478 D.13 Deprecated iterator primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479 D.14 Deprecated shared_ptr observers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1479 D.15 Deprecated standard code conversion facets . . . . . . . . . . . . . . . . . . . . . . . . . . 1479 D.16 Deprecated convenience conversion interfaces . . . . . . . . . . . . . . . . . . . . . . . . . 1481 Cross references 1486 Cross references from ISO C++ 2014 1507 Index 1509 Index of grammar productions 1542 Index of library names 1546 Index of implementation-defined behavior 1604 Contents ix ©ISO/IEC N4659 List of Tables 1 Alternative tokens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2 Ranges of characters allowed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3 Ranges of characters disallowed initially (combining characters) . . . . . . . . . . . . . . . . . . 27 4 Identifiers with special meaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6 Alternative representations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7 Types of integer literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8 Escape sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 9 String literal concatenations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10 Relations on const and volatile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 11 simple-type-specifiers and the types they specify . . . . . . . . . . . . . . . . . . . . . . . . . . 168 12 Relationship between operator and function call notation . . . . . . . . . . . . . . . . . . . . . 319 13 Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 14 Value of folding empty sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 15 Library categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447 16 C++ library headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 17 C++ headers for C library facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457 18 C standard Annex K names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 19 C++ headers for freestanding implementations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459 20 EqualityComparable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 21 LessThanComparable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 22 DefaultConstructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 23 MoveConstructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 460 24 CopyConstructible requirements (in addition to MoveConstructible) . . . . . . . . . . . . . 461 25 MoveAssignable requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 26 CopyAssignable requirements (in addition to MoveAssignable) . . . . . . . . . . . . . . . . . 461 27 Destructible requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 28 NullablePointer requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 29 Hash requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 30 Descriptive variable definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 31 Allocator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 32 Language support library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 478 33 Diagnostics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513 34 General utilities library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 530 35 optional::operator=(const optional&) effects . . . . . . . . . . . . . . . . . . . . . . . . . 560 36 optional::operator=(optional&&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560 37 optional::operator=(const optional&) effects . . . . . . . . . . . . . . . . . . . . . . . 561 38 optional::operator=(optional&&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 562 List of Tables x ©ISO/IEC N4659 39 optional::swap(optional&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564 40 Primary type category predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 684 41 Composite type category predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685 42 Type property predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 686 43 Type property queries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 693 44 Type relationship predicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694 45 Const-volatile modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695 46 Reference modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 696 47 Sign modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 697 48 Array modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 49 Pointer modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 698 50 Other transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 699 51 Expressions used to perform ratio arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . 704 52 Clock requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708 53 Strings library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 726 54 Character traits requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 727 55 basic_string(const Allocator&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742 56 basic_string(const basic_string&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 742 57 basic_string(const basic_string&, size_type, const Allocator&) and basic_string(const basic_string&, size_type, size_type, const Allocator&) effects 742 58 basic_string(const charT*, size_type, const Allocator&) effects . . . . . . . . . . . . . 743 59 basic_string(const charT*, const Allocator&) effects . . . . . . . . . . . . . . . . . . . . 743 60 basic_string(size_t, charT, const Allocator&) effects . . . . . . . . . . . . . . . . . . . 744 61 basic_string(const basic_string&, const Allocator&) and basic_string(basic_string&&, const Allocator&) effects . . . . . . . . . . . . . . . . 744 62 operator=(const basic_string&) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745 63 compare() results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759 64 basic_string_view(const charT*) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 770 65 basic_string_view(const charT*, size_type) effects . . . . . . . . . . . . . . . . . . . . . 770 66 compare() results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773 67 Additional basic_string_view comparison overloads . . . . . . . . . . . . . . . . . . . . . . . 775 68 Localization library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 782 69 Locale category facets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 786 70 Required specializations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 787 71 do_in/do_out result values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 72 do_unshift result values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 73 Integer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804 74 Length modifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804 75 Integer conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808 76 Floating-point conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808 77 Length modifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808 78 Numeric conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808 79 Fill padding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 809 80 do_get_date effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 816 81 Potential setlocale data races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 82 Containers library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 83 Container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 84 Reversible container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 List of Tables xi ©ISO/IEC N4659 85 Optional container operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 835 86 Allocator-aware container requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 836 87 Sequence container requirements (in addition to container) . . . . . . . . . . . . . . . . . . . . 838 88 Optional sequence container operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841 89 Container types with compatible nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 843 90 Associative container requirements (in addition to container) . . . . . . . . . . . . . . . . . . . 846 91 Unordered associative container requirements (in addition to container) . . . . . . . . . . . . . 857 92 Iterators library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955 93 Relations among iterator categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 955 94 Iterator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 957 95 Input iterator requirements (in addition to Iterator) . . . . . . . . . . . . . . . . . . . . . . . . 957 96 Output iterator requirements (in addition to Iterator) . . . . . . . . . . . . . . . . . . . . . . . 958 97 Forward iterator requirements (in addition to input iterator) . . . . . . . . . . . . . . . . . . . 959 98 Bidirectional iterator requirements (in addition to forward iterator) . . . . . . . . . . . . . . . . 960 99 Random access iterator requirements (in addition to bidirectional iterator) . . . . . . . . . . . 961 100 Algorithms library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 989 101 Numerics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050 102 Seed sequence requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1063 103 Uniform random bit generator requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064 104 Random number engine requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1065 105 Random number distribution requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1069 106 Input/output library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1157 107 fmtflags effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167 108 fmtflags constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167 109 iostate effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167 110 openmode effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1167 111 seekdir effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1168 112 Position type requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1172 113 basic_ios::init() effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1174 114 basic_ios::copyfmt() effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1175 115 seekoff positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1219 116 newoff values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1219 117 File open modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229 118 seekoff effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1231 119 filesystem_error(const string&, error_code) effects . . . . . . . . . . . . . . . . . . . . . 1264 120 filesystem_error(const string&, const path&, error_code) effects . . . . . . . . . . . . 1264 121 filesystem_error(const string&, const path&, const path&, error_code) effects . . . 1265 122 Enum path::format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265 123 Enum class file_type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266 124 Enum class copy_options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1266 125 Enum class perms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267 126 Enum class perm_options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1267 127 Enum class directory_options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1268 128 Regular expressions library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1297 129 Regular expression traits class requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1298 130 syntax_option_type effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1307 List of Tables xii ©ISO/IEC N4659 131 regex_constants::match_flag_type effects when obtaining a match against a character container sequence [first, last). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1308 132 error_type values in the C locale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1309 133 Character class names and corresponding ctype masks . . . . . . . . . . . . . . . . . . . . . . . 1313 134 match_results assignment operator effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1325 135 Effects of regex_match algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1329 136 Effects of regex_search algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1330 137 Atomics library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1342 138 Atomic arithmetic computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1353 139 Atomic pointer computations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1355 140 Thread support library summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1359 141 C headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1461 142 strstreambuf(streamsize) effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1463 143 strstreambuf(void* (*)(size_t), void (*)(void*)) effects . . . . . . . . . . . . . . . . . 1463 144 strstreambuf(charT*, streamsize, charT*) effects . . . . . . . . . . . . . . . . . . . . . . . 1464 145 seekoff positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 146 newoff values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1466 List of Tables xiii ©ISO/IEC N4659 List of Figures 1 Expression category taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 2 Directed acyclic graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 3 Non-virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 4 Virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 5 Virtual and non-virtual base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
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