Can't create a new thread (errno -1); if you are not out of available memory？？

koenemy 2011-07-18 11:34:31

Can't create a new thread (errno -1); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug -

mysql-5.5.13-win32.msi

[client]
port=3306
[mysql]
default-character-set=utf8
[mysqld]
port=3306
init-file=D:\database\data\load.sql
basedir="C:/Server_Core/MySQL/"
datadir="D:/database/Data/"
character-set-server=utf8
default-storage-engine=MYISAM
max_connections=1000
query_cache_size=64M
table_cache=256
tmp_table_size=256M
thread_cache_size=128
myisam_max_sort_file_size=100G
myisam_sort_buffer_size=128M
key_buffer_size=32M
read_buffer_size=2M
read_rnd_buffer_size=2M
sort_buffer_size=8M
thread_concurrency=8
max_connect_errors = 10000000
wait_timeout = 10
skip-innodb
log-bin
binlog-ignore-db=xxx
max_heap_table_size=2048M

mysql服务器。
10G内存，八核。windows2003
出现以上错误时内存使用5.8G。
max_connections=2000 设置成2000，现在改为1000，官网说500-1000.

wait_timeout = 10 这个是不是不起作用啊。
还是需要设置什么参数？？

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koenemy 2011-07-20

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顶回复内容太短了！

rucypli 2011-07-18

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myisam_max_sort_file_size=100G？？

ERROR 1135 (HY000): Can’t create a new thread (errno 11);if you are not out of available memory,you can consult the manual for a possible OS-dependent bug

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

Table of Contents Summary of gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Free Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Free Software Needs Free Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Contributors to gdb. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 A Sample gdb Session . . . . . . . . . . . . . . . . . . . . . . 7 2 Getting In and Out of gdb . . . . . . . . . . . . . . . . 11 2.1 Invoking gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Choosing Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Choosing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 What gdb Does During Startup . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Quitting gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Shell Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Logging Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 11 12 13 15 16 16 16 gdb Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.1 Command Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.2 Command Completion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3.3 Getting Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4 Running Programs Under gdb . . . . . . . . . . . . . 25 4.1 Compiling for Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Starting your Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Your Program’s Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Your Program’s Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Your Program’s Working Directory . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Your Program’s Input and Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Debugging an Already-running Process . . . . . . . . . . . . . . . . . . . . . . 4.8 Killing the Child Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Debugging Programs with Multiple Threads . . . . . . . . . . . . . . . . . . 4.10 Debugging Programs with Multiple Processes. . . . . . . . . . . . . . . . 4.11 Setting a Bookmark to Return to Later . . . . . . . . . . . . . . . . . . . . . 4.11.1 A Non-obvious Benefit of Using Checkpoints . . . . . . . . . . . . 5 25 26 28 28 29 29 30 31 31 34 36 37 Stopping and Continuing . . . . . . . . . . . . . . . . . . 39 5.1 Breakpoints, Watchpoints, and Catchpoints . . . . . . . . . . . . . . . . . . 5.1.1 Setting Breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Setting Watchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Setting Catchpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.4 Deleting Breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 40 45 47 49 ii Debugging with gdb 5.1.5 Disabling Breakpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.6 Break Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.7 Breakpoint Command Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.8 “Cannot insert breakpoints” . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.9 “Breakpoint address adjusted...” . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Continuing and Stepping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Stopping and Starting Multi-thread Programs . . . . . . . . . . . . . . . . 6 Examining the Stack . . . . . . . . . . . . . . . . . . . . . . 61 6.1 6.2 6.3 6.4 7 Stack Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Backtraces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Selecting a Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Information About a Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 62 64 65 Examining Source Files . . . . . . . . . . . . . . . . . . . 67 7.1 Printing Source Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Specifying a Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Editing Source Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Choosing your Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Searching Source Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Specifying Source Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Source and Machine Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 49 50 52 53 53 54 57 59 67 68 69 69 70 70 72 Examining Data . . . . . . . . . . . . . . . . . . . . . . . . . . 75 8.1 Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Ambiguous Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Program Variables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Artificial Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Output Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Examining Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Automatic Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Print Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9 Value History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.10 Convenience Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.11 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.12 Floating Point Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.13 Vector Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.14 Operating System Auxiliary Information . . . . . . . . . . . . . . . . . . . . 8.15 Memory Region Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15.1 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15.1.1 Memory Access Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15.1.2 Memory Access Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15.1.3 Data Cache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.15.2 Memory Access Checking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.16 Copy Between Memory and a File . . . . . . . . . . . . . . . . . . . . . . . . . . 8.17 How to Produce a Core File from Your Program . . . . . . . . . . . . . 75 76 77 79 79 81 82 84 90 90 92 93 94 94 94 95 95 96 96 96 96 97 iii 8.18 Character Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 8.19 Caching Data of Remote Targets . . . . . . . . . . . . . . . . . . . . . . . . . . 100 8.20 Search Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 9 C Preprocessor Macros . . . . . . . . . . . . . . . . . . 103 10 Tracepoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 10.1 Commands to Set Tracepoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Create and Delete Tracepoints . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 Enable and Disable Tracepoints . . . . . . . . . . . . . . . . . . . . . . . 10.1.3 Tracepoint Passcounts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.4 Tracepoint Action Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.5 Listing Tracepoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.6 Starting and Stopping Trace Experiments . . . . . . . . . . . . . 10.2 Using the Collected Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 tfind n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 tdump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 save-tracepoints filename . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Convenience Variables for Tracepoints . . . . . . . . . . . . . . . . . . . . . 11 Debugging Programs That Use Overlays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 11.1 11.2 11.3 11.4 12 107 107 108 108 109 110 110 111 111 113 114 114 How Overlays Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overlay Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Automatic Overlay Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overlay Sample Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 116 118 119 Using gdb with Different Languages . . . . . 121 12.1 Switching Between Source Languages . . . . . . . . . . . . . . . . . . . . . . 12.1.1 List of Filename Extensions and Languages . . . . . . . . . . . . 12.1.2 Setting the Working Language . . . . . . . . . . . . . . . . . . . . . . . . 12.1.3 Having gdb Infer the Source Language . . . . . . . . . . . . . . . . 12.2 Displaying the Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Type and Range Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.1 An Overview of Type Checking . . . . . . . . . . . . . . . . . . . . . . . 12.3.2 An Overview of Range Checking . . . . . . . . . . . . . . . . . . . . . . 12.4 Supported Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1 C and C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.1 C and C++ Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.2 C and C++ Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.3 C++ Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.4 C and C++ Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.5 C and C++ Type and Range Checks . . . . . . . . . . . . . . 12.4.1.6 gdb and C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.7 gdb Features for C++ . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1.8 Decimal Floating Point format . . . . . . . . . . . . . . . . . . . 12.4.2 Objective-C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 121 122 122 122 123 123 124 125 125 126 127 128 129 129 129 130 131 131 iv Debugging with gdb 12.4.2.1 Method Names in Commands . . . . . . . . . . . . . . . . . . . . 12.4.2.2 The Print Command With Objective-C . . . . . . . . . . . 12.4.3 Fortran . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.3.1 Fortran Operators and Expressions . . . . . . . . . . . . . . . 12.4.3.2 Fortran Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.3.3 Special Fortran Commands . . . . . . . . . . . . . . . . . . . . . . 12.4.4 Pascal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5 Modula-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5.1 Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5.2 Built-in Functions and Procedures . . . . . . . . . . . . . . . . 12.4.5.3 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5.4 Modula-2 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5.5 Modula-2 Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.5.6 Deviations from Standard Modula-2 . . . . . . . . . . . . . . 12.4.5.7 Modula-2 Type and Range Checks . . . . . . . . . . . . . . . 12.4.5.8 The Scope Operators :: and . . . . . . . . . . . . . . . . . . . . 12.4.5.9 gdb and Modula-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.6 Ada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.6.2 Omissions from Ada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.6.3 Additions to Ada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.6.4 Stopping at the Very Beginning . . . . . . . . . . . . . . . . . . 12.4.6.5 Known Peculiarities of Ada Mode . . . . . . . . . . . . . . . . 12.5 Unsupported Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 132 132 132 133 133 133 133 133 135 136 136 138 138 138 139 139 139 139 140 141 143 143 143 13 Examining the Symbol Table . . . . . . . . . . . . 145 14 Altering Execution . . . . . . . . . . . . . . . . . . . . . 151 14.1 14.2 14.3 14.4 14.5 14.6 15 Assignment to Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuing at a Different Address . . . . . . . . . . . . . . . . . . . . . . . . . Giving your Program a Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Returning from a Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calling Program Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Patching Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 152 153 153 154 154 gdb Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 15.1 Commands to Specify Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 15.2 Debugging Information in Separate Files . . . . . . . . . . . . . . . . . . . 163 15.3 Errors Reading Symbol Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 16 Specifying a Debugging Target . . . . . . . . . . 169 16.1 Active Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 16.2 Commands for Managing Targets . . . . . . . . . . . . . . . . . . . . . . . . . . 170 16.3 Choosing Target Byte Order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 v 17 Debugging Remote Programs . . . . . . . . . . . 173 17.1 Connecting to a Remote Target . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Sending files to a remote system . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Using the gdbserver Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.1 Running gdbserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.1.1 Attaching to a Running Program . . . . . . . . . . . . . . . . . 17.3.1.2 Multi-Process Mode for gdbserver . . . . . . . . . . . . . . . 17.3.1.3 Other Command-Line Arguments for gdbserver . . 17.3.2 Connecting to gdbserver . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3.3 Monitor Commands for gdbserver . . . . . . . . . . . . . . . . . . . . 17.4 Remote Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Implementing a Remote Stub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.1 What the Stub Can Do for You . . . . . . . . . . . . . . . . . . . . . . . 17.5.2 What You Must Do for the Stub . . . . . . . . . . . . . . . . . . . . . . 17.5.3 Putting it All Together. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 173 175 175 175 176 176 177 177 177 178 181 182 183 184 Configuration-Specific Information . . . . . . . 185 18.1 Native. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1.1 HP-UX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1.2 BSD libkvm Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1.3 SVR4 Process Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1.4 Features for Debugging djgpp Programs . . . . . . . . . . . . . . 18.1.5 Features for Debugging MS Windows PE Executables . . 18.1.5.1 Support for DLLs without Debugging Symbols . . . . 18.1.5.2 DLL Name Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.1.5.3 Working with Minimal Symbols . . . . . . . . . . . . . . . . . . 18.1.6 Commands Specific to gnu Hurd Systems . . . . . . . . . . . . . 18.1.7 QNX Neutrino . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2 Embedded Operating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1 Using gdb with VxWorks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.1 Connecting to VxWorks . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.2 VxWorks Download . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.3 Running Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Embedded Processors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1 ARM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.2 Renesas M32R/D and M32R/SDI . . . . . . . . . . . . . . . . . . . . . 18.3.3 M68k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.4 MIPS Embedded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.5 OpenRISC 1000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.6 PowerPC Embedded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.7 HP PA Embedded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.8 Tsqware Sparclet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.8.1 Setting File to Debug . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.8.2 Connecting to Sparclet . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.8.3 Sparclet Download . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.8.4 Running and Debugging . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.9 Fujitsu Sparclite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.10 Zilog Z8000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 185 185 185 187 189 190 190 191 192 194 194 194 195 195 196 196 196 198 199 199 201 203 204 204 204 205 205 205 205 205 vi Debugging with gdb 18.3.11 Atmel AVR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.12 CRIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.13 Renesas Super-H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4 Architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.1 x86 Architecture-specific Issues . . . . . . . . . . . . . . . . . . . . . . . 18.4.2 A29K . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3 Alpha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.4 MIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.5 HPPA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.6 Cell Broadband Engine SPU architecture . . . . . . . . . . . . . . 18.4.7 PowerPC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Controlling gdb . . . . . . . . . . . . . . . . . . . . . . . . 211 19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8 20 206 206 207 207 207 207 207 208 209 209 210 Prompt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command Editing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Screen Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Configuring the Current ABI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optional Warnings and Messages . . . . . . . . . . . . . . . . . . . . . . . . . . Optional Messages about Internal Happenings . . . . . . . . . . . . . . 211 211 211 213 214 214 215 217 Canned Sequences of Commands . . . . . . . . 221 20.1 20.2 20.3 20.4 User-defined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . User-defined Command Hooks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Command Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commands for Controlled Output . . . . . . . . . . . . . . . . . . . . . . . . . 221 222 223 224 21 Command Interpreters . . . . . . . . . . . . . . . . . . 227 22 gdb Text User Interface . . . . . . . . . . . . . . . . . 229 22.1 22.2 22.3 22.4 22.5 23 TUI Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TUI Key Bindings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TUI Single Key Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TUI-specific Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TUI Configuration Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 230 231 231 233 Using gdb under gnu Emacs . . . . . . . . . . . . 235 vii 24 The gdb/mi Interface . . . . . . . . . . . . . . . . . . . 237 Function and Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Notation and Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3 gdb/mi Command Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3.1 gdb/mi Input Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3.2 gdb/mi Output Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4 gdb/mi Compatibility with CLI . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5 gdb/mi Development and Front Ends . . . . . . . . . . . . . . . . . . . . . 24.6 gdb/mi Output Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.1 gdb/mi Result Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.2 gdb/mi Stream Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.3 gdb/mi Async Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.7 Simple Examples of gdb/mi Interaction. . . . . . . . . . . . . . . . . . . . 24.8 gdb/mi Command Description Format . . . . . . . . . . . . . . . . . . . . 24.9 gdb/mi Breakpoint Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.10 gdb/mi Program Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.11 gdb/mi Thread Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.12 gdb/mi Program Execution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.13 gdb/mi Stack Manipulation Commands . . . . . . . . . . . . . . . . . . 24.14 gdb/mi Variable Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.15 gdb/mi Data Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.16 gdb/mi Tracepoint Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.17 gdb/mi Symbol Query Commands . . . . . . . . . . . . . . . . . . . . . . . 24.18 gdb/mi File Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.19 gdb/mi Target Manipulation Commands . . . . . . . . . . . . . . . . . 24.20 gdb/mi File Transfer Commands . . . . . . . . . . . . . . . . . . . . . . . . . 24.21 Miscellaneous gdb/mi Commands . . . . . . . . . . . . . . . . . . . . . . . . 25 gdb Annotations . . . . . . . . . . . . . . . . . . . . . . . 293 25.1 25.2 25.3 25.4 25.5 25.6 25.7 26 237 237 237 237 238 240 240 240 240 241 241 242 243 244 251 254 255 261 265 271 277 277 280 283 287 288 What is an Annotation? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Server Prefix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Annotation for gdb Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Invalidation Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Running the Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Displaying Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 294 294 294 295 295 296 Reporting Bugs in gdb . . . . . . . . . . . . . . . . . . 297 26.1 Have You Found a Bug? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 26.2 How to Report Bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 viii Debugging with gdb 27 Command Line Editing . . . . . . . . . . . . . . . . . 301 27.1 Introduction to Line Editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2 Readline Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2.1 Readline Bare Essentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2.2 Readline Movement Commands . . . . . . . . . . . . . . . . . . . . . . . 27.2.3 Readline Killing Commands . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2.4 Readline Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2.5 Searching for Commands in the History . . . . . . . . . . . . . . . 27.3 Readline Init File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3.1 Readline Init File Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3.2 Conditional Init Constructs . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3.3 Sample Init File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4 Bindable Readline Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.1 Commands For Moving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.2 Commands For Manipulating The History . . . . . . . . . . . . . 27.4.3 Commands For Changing Text . . . . . . . . . . . . . . . . . . . . . . . 27.4.4 Killing And Yanking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.5 Specifying Numeric Arguments . . . . . . . . . . . . . . . . . . . . . . . 27.4.6 Letting Readline Type For You . . . . . . . . . . . . . . . . . . . . . . . 27.4.7 Keyboard Macros . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.8 Some Miscellaneous Commands . . . . . . . . . . . . . . . . . . . . . . . 27.5 Readline vi Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 301 301 301 302 302 303 303 304 304 309 310 313 313 313 315 316 317 317 317 318 319 Using History Interactively . . . . . . . . . . . . . . 321 28.1 History Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.1 Event Designators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.2 Word Designators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.3 Modifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 321 321 322 Appendix A Formatting Documentation . . . . 325 Appendix B Installing gdb . . . . . . . . . . . . . . . . 327 B.1 B.2 B.3 B.4 B.5 Requirements for Building gdb . . . . . . . . . . . . . . . . . . . . . . . . . . . . Invoking the gdb ‘configure’ Script . . . . . . . . . . . . . . . . . . . . . . . Compiling gdb in Another Directory . . . . . . . . . . . . . . . . . . . . . . . Specifying Names for Hosts and Targets . . . . . . . . . . . . . . . . . . . . ‘configure’ Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix C 327 327 329 330 330 Maintenance Commands . . . . . . 333 ix Appendix D gdb Remote Serial Protocol . . . 339 D.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.2 Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.3 Stop Reply Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.4 General Query Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.5 Register Packet Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.6 Tracepoint Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.7 Host I/O Packets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.8 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.9 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10 File-I/O Remote Protocol Extension . . . . . . . . . . . . . . . . . . . . . . D.10.1 File-I/O Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.2 Protocol Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.3 The F Request Packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.4 The F Reply Packet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.5 The ‘Ctrl-C’ Message . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.6 Console I/O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.7 List of Supported Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . close . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lseek . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . rename . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . unlink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . stat/fstat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . gettimeofday . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . isatty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.8 Protocol-specific Representation of Datatypes . . . . . . . . . Integral Datatypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pointer Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Memory Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . struct stat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . struct timeval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.9 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Open Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . mode t Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Errno Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lseek Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.10.10 File-I/O Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.11 Library List Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D.12 Memory Map Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 340 347 348 358 358 360 362 362 363 363 363 364 364 365 365 365 366 367 367 367 368 368 369 369 370 370 370 371 371 371 372 372 372 373 373 373 373 374 374 374 375 376 x Debugging with gdb Appendix E The GDB Agent Expression Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 E.1 E.2 E.3 E.4 E.5 E.6 General Bytecode Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bytecode Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Agent Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Varying Target Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tracing on Symmetrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix F 377 379 383 384 384 386 Target Descriptions . . . . . . . . . . . 389 F.1 Retrieving Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2 Target Description Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2.1 Inclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2.2 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2.3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2.4 Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.2.5 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.3 Predefined Target Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.4 Standard Target Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.4.1 ARM Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.4.2 MIPS Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.4.3 M68K Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F.4.4 PowerPC Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 390 390 390 391 391 391 392 393 393 393 394 394 Appendix G GNU GENERAL PUBLIC LICENSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION . . . . . . . . . . . . . . . . . . . 396 How to Apply These Terms to Your New Programs . . . . . . . . . . . . . . . 400 Appendix H GNU Free Documentation License . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 H.1 ADDENDUM: How to use this License for your documents . . 407 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409 1 Summary of gdb The purpose of a debugger such as gdb is to allow you to see what is going on “inside” another program while it executes—or what another program was doing at the moment it crashed. gdb can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act: • Start your program, specifying anything that might affect its behavior. • Make your program stop on specified conditions. • Examine what has happened, when your program has stopped. • Change things in your program, so you can experiment with correcting the effects of one bug and go on to learn about another. You can use gdb to debug programs written in C and C++. For more information, see Section 12.4 [Supported Languages], page 125. For more information, see Section 12.4.1 [C and C++], page 125. Support for Modula-2 is partial. [Modula-2], page 133. For information on Modula-2, see Section 12.4.5 Debugging Pascal programs which use sets, subranges, file variables, or nested functions does not currently work. gdb does not support entering expressions, printing values, or similar features using Pascal syntax. gdb can be used to debug programs written in Fortran, although it may be necessary to refer to some variables with a trailing underscore. gdb can be used to debug programs written in Objective-C, using either the Ap- ple/NeXT or the GNU Objective-C runtime. Free Software gdb is free software, protected by the gnu General Public License (GPL). The GPL gives you the freedom to copy or adapt a licensed program—but every person getting a copy also gets with it the freedom to modify that copy (which means that they must get access to the source code), and the freedom to distribute further copies. Typical software companies use copyrights to limit your freedoms; the Free Software Foundation uses the GPL to preserve these freedoms. Fundamentally, the General Public License is a license which says that you have these freedoms and that you cannot take these freedoms away from anyone else. Free Software Needs Free Documentation The biggest deficiency in the free software community today is not in the software—it is the lack of good free documentation that we can include with the free software. Many of our most important programs do not come with free reference manuals and free introductory texts. Documentation is an essential part of any software package; when an important free software package does not come with a free manual and a free tutorial, that is a major gap. We have many such gaps today. 2 Debugging with gdb Consider Perl, for instance. The tutorial manuals that people normally use are non-free. How did this come about? Because the authors of those manuals published them with restrictive terms—no copying, no modification, source files not available—which exclude them from the free software world. That wasn’t the first time this sort of thing happened, and it was far from the last. Many times we have heard a GNU user eagerly describe a manual that he is writing, his intended contribution to the community, only to learn that he had ruined everything by signing a publication contract to make it non-free. Free documentation, like free software, is a matter of freedom, not price. The problem with the non-free manual is not that publishers charge a price for printed copies—that in itself is fine. (The Free Software Foundation sells printed copies of manuals, too.) The problem is the restrictions on the use of the manual. Free manuals are available in source code form, and give you permission to copy and modify. Non-free manuals do not allow this. The criteria of freedom for a free manual are roughly the same as for free software. Redistribution (including the normal kinds of commercial redistribution) must be permitted, so that the manual can accompany every copy of the program, both on-line and on paper. Permission for modification of the technical content is crucial too. When people mod- ify the software, adding or changing features, if they are conscientious they will change the manual too—so they can provide accurate and clear documentation for the modified program. A manual that leaves you no choice but to write a new manual to document a changed version of the program is not really available to our community. Some kinds of limits on the way modification is handled are acceptable. For example, requirements to preserve the original author’s copyright notice, the distribution terms, or the list of authors, are ok. It is also no problem to require modified versions to include notice that they were modified. Even entire sections that may not be deleted or changed are acceptable, as long as they deal with nontechnical topics (like this one). These kinds of restrictions are acceptable because they don’t obstruct the community’s normal use of the manual. However, it must be possible to modify all the technical content of the manual, and then distribute the result in all the usual media, through all the usual channels. Otherwise, the restrictions obstruct the use of the manual, it is not free, and we need another manual to replace it. Please spread the word about this issue. Our community continues to lose manuals to proprietary publishing. If we spread the word that free software needs free reference manuals and free tutorials, perhaps the next person who wants to contribute by writing documentation will realize, before it is too late, that only free manuals contribute to the free software community. If you are writing documentation, please insist on publishing it under the GNU Free Documentation License or another free documentation license. Remember that this deci- sion requires your approval—you don’t have to let the publisher decide. Some commercial publishers will use a free license if you insist, but they will not propose the option; it is up to you to raise the issue and say firmly that this is what you want. If the publisher you are dealing with refuses, please try other publishers. If you’re not sure whether a proposed license is free, write to licensing@gnu.org. 3 You can encourage commercial publishers to sell more free, copylefted manuals and tutorials by buying them, and particularly by buying copies from the publishers that paid for their writing or for major improvements. Meanwhile, try to avoid buying non-free documentation at all. Check the distribution terms of a manual before you buy it, and insist that whoever seeks your business must respect your freedom. Check the history of the book, and try to reward the publishers that have paid or pay the authors to work on it. The Free Software Foundation maintains a list of free documentation published by other publishers, at http://www.fsf.org/doc/other-free-books.html. Contributors to gdb Richard Stallman was the original author of gdb, and of many other gnu programs. Many others have contributed to its development. This section attempts to credit major contrib- utors. One of the virtues of free software is that everyone is free to contribute to it; with regret, we cannot actually acknowledge everyone here. The file ‘ChangeLog’ in the gdb distribution approximates a blow-by-blow account. Changes much prior to version 2.0 are lost in the mists of time. Plea: Additions to this section are particularly welcome. If you or your friends (or enemies, to be evenhanded) have been unfairly omitted from this list, we would like to add your names! So that they may not regard their many labors as thankless, we particularly thank those who shepherded gdb through major releases: Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0); Jim Blandy (release 4.18); Jason Molenda (release 4.17); Stan Shebs (release 4.14); Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9); Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4); John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim Kingdon (releases 3.5, 3.4, and 3.3); and Randy Smith (releases 3.2, 3.1, and 3.0). Richard Stallman, assisted at various times by Peter TerMaat, Chris Hanson, and Richard Mlynarik, handled releases through 2.8. Michael Tiemann is the author of most of the gnu C++ support in gdb, with significant additional contributions from Per Bothner and Daniel Berlin. James Clark wrote the gnu C++ demangler. Early work on C++ was by Peter TerMaat (who also did much general update work leading to release 3.0). gdb uses the BFD subroutine library to examine multiple object-file formats; BFD was a joint project of David V. Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. David Johnson wrote the original COFF support; Pace Willison did the original support for encapsulated COFF. Brent Benson of Harris Computer Systems contributed DWARF 2 support. Adam de Boor and Bradley Davis contributed the ISI Optimum V support. Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS support. Jean-Daniel Fekete contributed Sun 386i support. Chris Hanson improved the HP9000 support. Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support. David Johnson con- tributed Encore Umax support. Jyrki Kuoppala contributed Altos 3068 support. Jeff Law contributed HP PA and SOM support. Keith Packard contributed NS32K support. 4 Debugging with gdb Doug Rabson contributed Acorn Risc Machine support. Bob Rusk contributed Harris Nighthawk CX-UX support. Chris Smith contributed Convex support (and Fortran de- bugging). Jonathan Stone contributed Pyramid support. Michael Tiemann contributed SPARC support. Tim Tucker contributed support for the Gould NP1 and Gould Powern- ode. Pace Willison contributed Intel 386 support. Jay Vosburgh contributed Symmetry support. Marko Mlinar contributed OpenRISC 1000 support. Andreas Schwab contributed M68K gnu/Linux support. Rich Schaefer and Peter Schauer helped with support of SunOS shared libraries. Jay Fenlason and Roland McGrath ensured that gdb and GAS agree about several machine instruction sets. Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM contributed remote debugging modules for the i960, VxWorks, A29K UDI, and RDI targets, respectively. Brian Fox is the author of the readline libraries providing command-line editing and command history. Andrew Beers of SUNY Buffalo wrote the language-switching code, the Modula-2 sup- port, and contributed the Languages chapter of this manual. Fred Fish wrote most of the support for Unix System Vr4. He also enhanced the command-completion support to cover C++ overloaded symbols. Hitachi America (now Renesas America), Ltd. H8/500, and Super-H processors. sponsored the support for H8/300, NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors. Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D proces- sors. Toshiba sponsored the support for the TX39 Mips processor. Matsushita sponsored the support for the MN10200 and MN10300 processors. Fujitsu sponsored the support for SPARClite and FR30 processors. Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware watchpoints. Michael Snyder added support for tracepoints. Stu Grossman wrote gdbserver. Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made nearly innumerable bug fixes and cleanups throughout gdb. The following people at the Hewlett-Packard Company contributed support for the PA- RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0 (narrow mode), HP’s implementation of kernel threads, HP’s aC++ compiler, and the Text User Interface (nee Terminal User Interface): Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific information in this manual. DJ Delorie ported gdb to MS-DOS, for the DJGPP project. Robert Hoehne made significant contributions to the DJGPP port. Cygnus Solutions has sponsored gdb maintenance and much of its development since 1991. Cygnus engineers who have worked on gdb fulltime include Mark Alexander, Jim 5 Blandy, Per Bothner, Kevin Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler, Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton, JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner, Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David Zuhn have made contributions both large and small. Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for Cygnus Solu- tions, implemented the original gdb/mi interface. Jim Blandy added support for preprocessor macros, while working for Red Hat. Andrew Cagney designed gdb’s architecture vector. Many people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick Duffek, Richard Henderson, Mark Ket- tenis, Grace Sainsbury, Kei Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped with the migration of old architectures to this new framework. Andrew Cagney completely re-designed and re-implemented gdb’s unwinder framework, this consisting of a fresh new design featuring frame IDs, independent frame sniffers, and the sentinel frame. Mark Kettenis implemented the dwarf 2 unwinder, Jeff Johnston the libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and trad unwinders. The architecture-specific changes, each involving a complete rewrite of the architecture’s frame code, were carried out by Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich Weigand. Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from Tensilica, Inc. contributed support for Xtensa processors. Others who have worked on the Xtensa port of gdb in the past include Steve Tjiang, John Newlin, and Scott Foehner.

Python参考手册，官方正式版参考手册，chm版。以下摘取部分内容:Navigation index modules | next | Python » 3.6.5 Documentation » Python Documentation contents What’s New in Python What’s New In Python 3.6 Summary – Release highlights New Features PEP 498: Formatted string literals PEP 526: Syntax for variable annotations PEP 515: Underscores in Numeric Literals PEP 525: Asynchronous Generators PEP 530: Asynchronous Comprehensions PEP 487: Simpler customization of class creation PEP 487: Descriptor Protocol Enhancements PEP 519: Adding a file system path protocol PEP 495: Local Time Disambiguation PEP 529: Change Windows filesystem encoding to UTF-8 PEP 528: Change Windows console encoding to UTF-8 PEP 520: Preserving Class Attribute Definition Order PEP 468: Preserving Keyword Argument Order New dict implementation PEP 523: Adding a frame evaluation API to CPython PYTHONMALLOC environment variable DTrace and SystemTap probing support Other Language Changes New Modules secrets Improved Modules array ast asyncio binascii cmath collections concurrent.futures contextlib datetime decimal distutils email encodings enum faulthandler fileinput hashlib http.client idlelib and IDLE importlib inspect json logging math multiprocessing os pathlib pdb pickle pickletools pydoc random re readline rlcompleter shlex site sqlite3 socket socketserver ssl statistics struct subprocess sys telnetlib time timeit tkinter traceback tracemalloc typing unicodedata unittest.mock urllib.request urllib.robotparser venv warnings winreg winsound xmlrpc.client zipfile zlib Optimizations Build and C API Changes Other Improvements Deprecated New Keywords Deprecated Python behavior Deprecated Python modules, functions and methods asynchat asyncore dbm distutils grp importlib os re ssl tkinter venv Deprecated functions and types of the C API Deprecated Build Options Removed API and Feature Removals Porting to Python 3.6 Changes in ‘python’ Command Behavior Changes in the Python API Changes in the C API CPython bytecode changes Notable changes in Python 3.6.2 New make regen-all build target Removal of make touch build target Notable changes in Python 3.6.5 What’s New In Python 3.5 Summary – Release highlights New Features PEP 492 - Coroutines with async and await syntax PEP 465 - A dedicated infix operator for matrix multiplication PEP 448 - Additional Unpacking Generalizations PEP 461 - percent formatting support for bytes and bytearray PEP 484 - Type Hints PEP 471 - os.scandir() function – a better and faster directory iterator PEP 475: Retry system calls failing with EINTR PEP 479: Change StopIteration handling inside generators PEP 485: A function for testing approximate equality PEP 486: Make the Python Launcher aware of virtual environments PEP 488: Elimination of PYO files PEP 489: Multi-phase extension module initialization Other Language Changes New Modules typing zipapp Improved Modules argparse asyncio bz2 cgi cmath code collections collections.abc compileall concurrent.futures configparser contextlib csv curses dbm difflib distutils doctest email enum faulthandler functools glob gzip heapq http http.client idlelib and IDLE imaplib imghdr importlib inspect io ipaddress json linecache locale logging lzma math multiprocessing operator os pathlib pickle poplib re readline selectors shutil signal smtpd smtplib sndhdr socket ssl Memory BIO Support Application-Layer Protocol Negotiation Support Other Changes sqlite3 subprocess sys sysconfig tarfile threading time timeit tkinter traceback types unicodedata unittest unittest.mock urllib wsgiref xmlrpc xml.sax zipfile Other module-level changes Optimizations Build and C API Changes Deprecated New Keywords Deprecated Python Behavior Unsupported Operating Systems Deprecated Python modules, functions and methods Removed API and Feature Removals Porting to Python 3.5 Changes in Python behavior Changes in the Python API Changes in the C API What’s New In Python 3.4 Summary – Release Highlights New Features PEP 453: Explicit Bootstrapping of PIP in Python Installations Bootstrapping pip By Default Documentation Changes PEP 446: Newly Created File Descriptors Are Non-Inheritable Improvements to Codec Handling PEP 451: A ModuleSpec Type for the Import System Other Language Changes New Modules asyncio ensurepip enum pathlib selectors statistics tracemalloc Improved Modules abc aifc argparse audioop base64 collections colorsys contextlib dbm dis doctest email filecmp functools gc glob hashlib hmac html http idlelib and IDLE importlib inspect ipaddress logging marshal mmap multiprocessing operator os pdb pickle plistlib poplib pprint pty pydoc re resource select shelve shutil smtpd smtplib socket sqlite3 ssl stat struct subprocess sunau sys tarfile textwrap threading traceback types urllib unittest venv wave weakref xml.etree zipfile CPython Implementation Changes PEP 445: Customization of CPython Memory Allocators PEP 442: Safe Object Finalization PEP 456: Secure and Interchangeable Hash Algorithm PEP 436: Argument Clinic Other Build and C API Changes Other Improvements Significant Optimizations Deprecated Deprecations in the Python API Deprecated Features Removed Operating Systems No Longer Supported API and Feature Removals Code Cleanups Porting to Python 3.4 Changes in ‘python’ Command Behavior Changes in the Python API Changes in the C API Changed in 3.4.3 PEP 476: Enabling certificate verification by default for stdlib http clients What’s New In Python 3.3 Summary – Release highlights PEP 405: Virtual Environments PEP 420: Implicit Namespace Packages PEP 3118: New memoryview implementation and buffer protocol documentation Features API changes PEP 393: Flexible String Representation Functionality Performance and resource usage PEP 397: Python Launcher for Windows PEP 3151: Reworking the OS and IO exception hierarchy PEP 380: Syntax for Delegating to a Subgenerator PEP 409: Suppressing exception context PEP 414: Explicit Unicode literals PEP 3155: Qualified name for classes and functions PEP 412: Key-Sharing Dictionary PEP 362: Function Signature Object PEP 421: Adding sys.implementation SimpleNamespace Using importlib as the Implementation of Import New APIs Visible Changes Other Language Changes A Finer-Grained Import Lock Builtin functions and types New Modules faulthandler ipaddress lzma Improved Modules abc array base64 binascii bz2 codecs collections contextlib crypt curses datetime decimal Features API changes email Policy Framework Provisional Policy with New Header API Other API Changes ftplib functools gc hmac http html imaplib inspect io itertools logging math mmap multiprocessing nntplib os pdb pickle pydoc re sched select shlex shutil signal smtpd smtplib socket socketserver sqlite3 ssl stat struct subprocess sys tarfile tempfile textwrap threading time types unittest urllib webbrowser xml.etree.ElementTree zlib Optimizations Build and C API Changes Deprecated Unsupported Operating Systems Deprecated Python modules, functions and methods Deprecated functions and types of the C API Deprecated features Porting to Python 3.3 Porting Python code Porting C code Building C extensions Command Line Switch Changes What’s New In Python 3.2 PEP 384: Defining a Stable ABI PEP 389: Argparse Command Line Parsing Module PEP 391: Dictionary Based Configuration for Logging PEP 3148: The concurrent.futures module PEP 3147: PYC Repository Directories PEP 3149: ABI Version Tagged .so Files PEP 3333: Python Web Server Gateway Interface v1.0.1 Other Language Changes New, Improved, and Deprecated Modules email elementtree functools itertools collections threading datetime and time math abc io reprlib logging csv contextlib decimal and fractions ftp popen select gzip and zipfile tarfile hashlib ast os shutil sqlite3 html socket ssl nntp certificates imaplib http.client unittest random poplib asyncore tempfile inspect pydoc dis dbm ctypes site sysconfig pdb configparser urllib.parse mailbox turtledemo Multi-threading Optimizations Unicode Codecs Documentation IDLE Code Repository Build and C API Changes Porting to Python 3.2 What’s New In Python 3.1 PEP 372: Ordered Dictionaries PEP 378: Format Specifier for Thousands Separator Other Language Changes New, Improved, and Deprecated Modules Optimizations IDLE Build and C API Changes Porting to Python 3.1 What’s New In Python 3.0 Common Stumbling Blocks Print Is A Function Views And Iterators Instead Of Lists Ordering Comparisons Integers Text Vs. Data Instead Of Unicode Vs. 8-bit Overview Of Syntax Changes New Syntax Changed Syntax Removed Syntax Changes Already Present In Python 2.6 Library Changes PEP 3101: A New Approach To String Formatting Changes To Exceptions Miscellaneous Other Changes Operators And Special Methods Builtins Build and C API Changes Performance Porting To Python 3.0 What’s New in Python 2.7 The Future for Python 2.x Changes to the Handling of Deprecation Warnings Python 3.1 Features PEP 372: Adding an Ordered Dictionary to collections PEP 378: Format Specifier for Thousands Separator PEP 389: The argparse Module for Parsing Command Lines PEP 391: Dictionary-Based Configuration For Logging PEP 3106: Dictionary Views PEP 3137: The memoryview Object Other Language Changes Interpreter Changes Optimizations New and Improved Modules New module: importlib New module: sysconfig ttk: Themed Widgets for Tk Updated module: unittest Updated module: ElementTree 1.3 Build and C API Changes Capsules Port-Specific Changes: Windows Port-Specific Changes: Mac OS X Port-Specific Changes: FreeBSD Other Changes and Fixes Porting to Python 2.7 New Features Added to Python 2.7 Maintenance Releases PEP 434: IDLE Enhancement Exception for All Branches PEP 466: Network Security Enhancements for Python 2.7 Acknowledgements What’s New in Python 2.6 Python 3.0 Changes to the Development Process New Issue Tracker: Roundup New Documentation Format: reStructuredText Using Sphinx PEP 343: The ‘with’ statement Writing Context Managers The contextlib module PEP 366: Explicit Relative Imports From a Main Module PEP 370: Per-user site-packages Directory PEP 371: The multiprocessing Package PEP 3101: Advanced String Formatting PEP 3105: print As a Function PEP 3110: Exception-Handling Changes PEP 3112: Byte Literals PEP 3116: New I/O Library PEP 3118: Revised Buffer Protocol PEP 3119: Abstract Base Classes PEP 3127: Integer Literal Support and Syntax PEP 3129: Class Decorators PEP 3141: A Type Hierarchy for Numbers The fractions Module Other Language Changes Optimizations Interpreter Changes New and Improved Modules The ast module The future_builtins module The json module: JavaScript Object Notation The plistlib module: A Property-List Parser ctypes Enhancements Improved SSL Support Deprecations and Removals Build and C API Changes Port-Specific Changes: Windows Port-Specific Changes: Mac OS X Port-Specific Changes: IRIX Porting to Python 2.6 Acknowledgements What’s New in Python 2.5 PEP 308: Conditional Expressions PEP 309: Partial Function Application PEP 314: Metadata for Python Software Packages v1.1 PEP 328: Absolute and Relative Imports PEP 338: Executing Modules as Scripts PEP 341: Unified try/except/finally PEP 342: New Generator Features PEP 343: The ‘with’ statement Writing Context Managers The contextlib module PEP 352: Exceptions as New-Style Classes PEP 353: Using ssize_t as the index type PEP 357: The ‘__index__’ method Other Language Changes Interactive Interpreter Changes Optimizations New, Improved, and Removed Modules The ctypes package The ElementTree package The hashlib package The sqlite3 package The wsgiref package Build and C API Changes Port-Specific Changes Porting to Python 2.5 Acknowledgements What’s New in Python 2.4 PEP 218: Built-In Set Objects PEP 237: Unifying Long Integers and Integers PEP 289: Generator Expressions PEP 292: Simpler String Substitutions PEP 318: Decorators for Functions and Methods PEP 322: Reverse Iteration PEP 324: New subprocess Module PEP 327: Decimal Data Type Why is Decimal needed? The Decimal type The Context type PEP 328: Multi-line Imports PEP 331: Locale-Independent Float/String Conversions Other Language Changes Optimizations New, Improved, and Deprecated Modules cookielib doctest Build and C API Changes Port-Specific Changes Porting to Python 2.4 Acknowledgements What’s New in Python 2.3 PEP 218: A Standard Set Datatype PEP 255: Simple Generators PEP 263: Source Code Encodings PEP 273: Importing Modules from ZIP Archives PEP 277: Unicode file name support for Windows NT PEP 278: Universal Newline Support PEP 279: enumerate() PEP 282: The logging Package PEP 285: A Boolean Type PEP 293: Codec Error Handling Callbacks PEP 301: Package Index and Metadata for Distutils PEP 302: New Import Hooks PEP 305: Comma-separated Files PEP 307: Pickle Enhancements Extended Slices Other Language Changes String Changes Optimizations New, Improved, and Deprecated Modules Date/Time Type The optparse Module Pymalloc: A Specialized Object Allocator Build and C API Changes Port-Specific Changes Other Changes and Fixes Porting to Python 2.3 Acknowledgements What’s New in Python 2.2 Introduction PEPs 252 and 253: Type and Class Changes Old and New Classes Descriptors Multiple Inheritance: The Diamond Rule Attribute Access Related Links PEP 234: Iterators PEP 255: Simple Generators PEP 237: Unifying Long Integers and Integers PEP 238: Changing the Division Operator Unicode Changes PEP 227: Nested Scopes New and Improved Modules Interpreter Changes and Fixes Other Changes and Fixes Acknowledgements What’s New in Python 2.1 Introduction PEP 227: Nested Scopes PEP 236: __future__ Directives PEP 207: Rich Comparisons PEP 230: Warning Framework PEP 229: New Build System PEP 205: Weak References PEP 232: Function Attributes PEP 235: Importing Modules on Case-Insensitive Platforms PEP 217: Interactive Display Hook PEP 208: New Coercion Model PEP 241: Metadata in Python Packages New and Improved Modules Other Changes and Fixes Acknowledgements What’s New in Python 2.0 Introduction What About Python 1.6? New Development Process Unicode List Comprehensions Augmented Assignment String Methods Garbage Collection of Cycles Other Core Changes Minor Language Changes Changes to Built-in Functions Porting to 2.0 Extending/Embedding Changes Distutils: Making Modules Easy to Install XML Modules SAX2 Support DOM Support Relationship to PyXML Module changes New modules IDLE Improvements Deleted and Deprecated Modules Acknowledgements Changelog Python 3.6.5 final? Tests Build Python 3.6.5 release candidate 1? Security Core and Builtins Library Documentation Tests Build Windows macOS IDLE Tools/Demos C API Python 3.6.4 final? Python 3.6.4 release candidate 1? Core and Builtins Library Documentation Tests Build Windows macOS IDLE Tools/Demos C API Python 3.6.3 final? Library Build Python 3.6.3 release candidate 1? Security Core and Builtins Library Documentation Tests Build Windows IDLE Tools/Demos Python 3.6.2 final? Python 3.6.2 release candidate 2? Security Python 3.6.2 release candidate 1? Core and Builtins Library Security Library IDLE C API Build Documentation Tools/Demos Tests Windows Python 3.6.1 final? Core and Builtins Build Python 3.6.1 release candidate 1? Core and Builtins Library IDLE Windows C API Documentation Tests Build Python 3.6.0 final? Python 3.6.0 release candidate 2? Core and Builtins Tools/Demos Windows Build Python 3.6.0 release candidate 1? Core and Builtins Library C API Documentation Tools/Demos Python 3.6.0 beta 4? Core and Builtins Library Documentation Tests Build Python 3.6.0 beta 3? Core and Builtins Library Windows Build Tests Python 3.6.0 beta 2? Core and Builtins Library Windows C API Build Tests Python 3.6.0 beta 1? Core and Builtins Library IDLE C API Tests Build Tools/Demos Windows Python 3.6.0 alpha 4? Core and Builtins Library IDLE Tests Windows Build Python 3.6.0 alpha 3? Core and Builtins Library Security Library Security Library IDLE C API Build Tools/Demos Documentation Tests Python 3.6.0 alpha 2? Core and Builtins Library Security Library Security Library IDLE Documentation Tests Windows Build Windows C API Tools/Demos Python 3.6.0 alpha 1? Core and Builtins Library Security Library Security Library Security Library IDLE Documentation Tests Build Windows Tools/Demos C API Python 3.5.3 final? Python 3.5.3 release candidate 1? Core and Builtins Library Security Library Security Library IDLE C API Documentation Tests Tools/Demos Windows Build Python 3.5.2 final? Core and Builtins Tests IDLE Python 3.5.2 release candidate 1? Core and Builtins Security Library Security Library Security Library Security Library Security Library IDLE Documentation Tests Build Windows Tools/Demos Windows Python 3.5.1 final? Core and Builtins Windows Python 3.5.1 release candidate 1? Core and Builtins Library IDLE Documentation Tests Build Windows Tools/Demos Python 3.5.0 final? Build Python 3.5.0 release candidate 4? Library Build Python 3.5.0 release candidate 3? Core and Builtins Library Python 3.5.0 release candidate 2? Core and Builtins Library Python 3.5.0 release candidate 1? Core and Builtins Library IDLE Documentation Tests Python 3.5.0 beta 4? Core and Builtins Library Build Python 3.5.0 beta 3? Core and Builtins Library Tests Documentation Build Python 3.5.0 beta 2? Core and Builtins Library Python 3.5.0 beta 1? Core and Builtins Library IDLE Tests Documentation Tools/Demos Python 3.5.0 alpha 4? Core and Builtins Library Build Tests Tools/Demos C API Python 3.5.0 alpha 3? Core and Builtins Library Build Tests Tools/Demos Python 3.5.0 alpha 2? Core and Builtins Library Build C API Windows Python 3.5.0 alpha 1? Core and Builtins Library IDLE Build C API Documentation Tests Tools/Demos Windows The Python Tutorial 1. Whetting Your Appetite 2. Using the Python Interpreter 2.1. Invoking the Interpreter 2.1.1. Argument Passing 2.1.2. Interactive Mode 2.2. The Interpreter and Its Environment 2.2.1. Source Code Encoding 3. An Informal Introduction to Python 3.1. Using Python as a Calculator 3.1.1. Numbers 3.1.2. Strings 3.1.3. Lists 3.2. First Steps Towards Programming 4. More Control Flow Tools 4.1. if Statements 4.2. for Statements 4.3. The range() Function 4.4. break and continue Statements, and else Clauses on Loops 4.5. pass Statements 4.6. Defining Functions 4.7. More on Defining Functions 4.7.1. Default Argument Values 4.7.2. Keyword Arguments 4.7.3. Arbitrary Argument Lists 4.7.4. Unpacking Argument Lists 4.7.5. Lambda Expressions 4.7.6. Documentation Strings 4.7.7. Function Annotations 4.8. Intermezzo: Coding Style 5. Data Structures 5.1. More on Lists 5.1.1. Using Lists as Stacks 5.1.2. Using Lists as Queues 5.1.3. List Comprehensions 5.1.4. Nested List Comprehensions 5.2. The del statement 5.3. Tuples and Sequences 5.4. Sets 5.5. Dictionaries 5.6. Looping Techniques 5.7. More on Conditions 5.8. Comparing Sequences and Other Types 6. Modules 6.1. More on Modules 6.1.1. Executing modules as scripts 6.1.2. The Module Search Path 6.1.3. “Compiled” Python files 6.2. Standard Modules 6.3. The dir() Function 6.4. Packages 6.4.1. Importing * From a Package 6.4.2. Intra-package References 6.4.3. Packages in Multiple Directories 7. Input and Output 7.1. Fancier Output Formatting 7.1.1. Old string formatting 7.2. Reading and Writing Files 7.2.1. Methods of File Objects 7.2.2. Saving structured data with json 8. Errors and Exceptions 8.1. Syntax Errors 8.2. Exceptions 8.3. Handling Exceptions 8.4. Raising Exceptions 8.5. User-defined Exceptions 8.6. Defining Clean-up Actions 8.7. Predefined Clean-up Actions 9. Classes 9.1. A Word About Names and Objects 9.2. Python Scopes and Namespaces 9.2.1. Scopes and Namespaces Example 9.3. A First Look at Classes 9.3.1. Class Definition Syntax 9.3.2. Class Objects 9.3.3. Instance Objects 9.3.4. Method Objects 9.3.5. Class and Instance Variables 9.4. Random Remarks 9.5. Inheritance 9.5.1. Multiple Inheritance 9.6. Private Variables 9.7. Odds and Ends 9.8. Iterators 9.9. Generators 9.10. Generator Expressions 10. Brief Tour of the Standard Library 10.1. Operating System Interface 10.2. File Wildcards 10.3. Command Line Arguments 10.4. Error Output Redirection and Program Termination 10.5. String Pattern Matching 10.6. Mathematics 10.7. Internet Access 10.8. Dates and Times 10.9. Data Compression 10.10. Performance Measurement 10.11. Quality Control 10.12. Batteries Included 11. Brief Tour of the Standard Library — Part II 11.1. Output Formatting 11.2. Templating 11.3. Working with Binary Data Record Layouts 11.4. Multi-threading 11.5. Logging 11.6. Weak References 11.7. Tools for Working with Lists 11.8. Decimal Floating Point Arithmetic 12. Virtual Environments and Packages 12.1. Introduction 12.2. Creating Virtual Environments 12.3. Managing Packages with pip 13. What Now? 14. Interactive Input Editing and History Substitution 14.1. Tab Completion and History Editing 14.2. Alternatives to the Interactive Interpreter 15. Floating Point Arithmetic: Issues and Limitations 15.1. Representation Error 16. Appendix 16.1. Interactive Mode 16.1.1. Error Handling 16.1.2. Executable Python Scripts 16.1.3. The Interactive Startup File 16.1.4. The Customization Modules Python Setup and Usage 1. Command line and environment 1.1. Command line 1.1.1. Interface options 1.1.2. Generic options 1.1.3. Miscellaneous options 1.1.4. Options you shouldn’t use 1.2. Environment variables 1.2.1. Debug-mode variables 2. Using Python on Unix platforms 2.1. Getting and installing the latest version of Python 2.1.1. On Linux 2.1.2. On FreeBSD and OpenBSD 2.1.3. On OpenSolaris 2.2. Building Python 2.3. Python-related paths and files 2.4. Miscellaneous 2.5. Editors and IDEs 3. Using Python on Windows 3.1. Installing Python 3.1.1. Supported Versions 3.1.2. Installation Steps 3.1.3. Removing the MAX_PATH Limitation 3.1.4. Installing Without UI 3.1.5. Installing Without Downloading 3.1.6. Modifying an install 3.1.7. Other Platforms 3.2. Alternative bundles 3.3. Configuring Python 3.3.1. Excursus: Setting environment variables 3.3.2. Finding the Python executable 3.4. Python Launcher for Windows 3.4.1. Getting started 3.4.1.1. From the command-line 3.4.1.2. Virtual environments 3.4.1.3. From a script 3.4.1.4. From file associations 3.4.2. Shebang Lines 3.4.3. Arguments in shebang lines 3.4.4. Customization 3.4.4.1. Customization via INI files 3.4.4.2. Customizing default Python versions 3.4.5. Diagnostics 3.5. Finding modules 3.6. Additional modules 3.6.1. PyWin32 3.6.2. cx_Freeze 3.6.3. WConio 3.7. Compiling Python on Windows 3.8. Embedded Distribution 3.8.1. Python Application 3.8.2. Embedding Python 3.9. Other resources 4. Using Python on a Macintosh 4.1. Getting and Installing MacPython 4.1.1. How to run a Python script 4.1.2. Running scripts with a GUI 4.1.3. Configuration 4.2. The IDE 4.3. Installing Additional Python Packages 4.4. GUI Programming on the Mac 4.5. Distributing Python Applications on the Mac 4.6. Other Resources The Python Language Reference 1. Introduction 1.1. Alternate Implementations 1.2. Notation 2. Lexical analysis 2.1. Line structure 2.1.1. Logical lines 2.1.2. Physical lines 2.1.3. Comments 2.1.4. Encoding declarations 2.1.5. Explicit line joining 2.1.6. Implicit line joining 2.1.7. Blank lines 2.1.8. Indentation 2.1.9. Whitespace between tokens 2.2. Other tokens 2.3. Identifiers and keywords 2.3.1. Keywords 2.3.2. Reserved classes of identifiers 2.4. Literals 2.4.1. String and Bytes literals 2.4.2. String literal concatenation 2.4.3. Formatted string literals 2.4.4. Numeric literals 2.4.5. Integer literals 2.4.6. Floating point literals 2.4.7. Imaginary literals 2.5. Operators 2.6. Delimiters 3. Data model 3.1. Objects, values and types 3.2. The standard type hierarchy 3.3. Special method names 3.3.1. Basic customization 3.3.2. Customizing attribute access 3.3.2.1. Customizing module attribute access 3.3.2.2. Implementing Descriptors 3.3.2.3. Invoking Descriptors 3.3.2.4. __slots__ 3.3.2.4.1. Notes on using __slots__ 3.3.3. Customizing class creation 3.3.3.1. Metaclasses 3.3.3.2. Determining the appropriate metaclass 3.3.3.3. Preparing the class namespace 3.3.3.4. Executing the class body 3.3.3.5. Creating the class object 3.3.3.6. Metaclass example 3.3.4. Customizing instance and subclass checks 3.3.5. Emulating callable objects 3.3.6. Emulating container types 3.3.7. Emulating numeric types 3.3.8. With Statement Context Managers 3.3.9. Special method lookup 3.4. Coroutines 3.4.1. Awaitable Objects 3.4.2. Coroutine Objects 3.4.3. Asynchronous Iterators 3.4.4. Asynchronous Context Managers 4. Execution model 4.1. Structure of a program 4.2. Naming and binding 4.2.1. Binding of names 4.2.2. Resolution of names 4.2.3. Builtins and restricted execution 4.2.4. Interaction with dynamic features 4.3. Exceptions 5. The import system 5.1. importlib 5.2. Packages 5.2.1. Regular packages 5.2.2. Namespace packages 5.3. Searching 5.3.1. The module cache 5.3.2. Finders and loaders 5.3.3. Import hooks 5.3.4. The meta path 5.4. Loading 5.4.1. Loaders 5.4.2. Submodules 5.4.3. Module spec 5.4.4. Import-related module attributes 5.4.5. module.__path__ 5.4.6. Module reprs 5.5. The Path Based Finder 5.5.1. Path entry finders 5.5.2. Path entry finder protocol 5.6. Replacing the standard import system 5.7. Special considerations for __main__ 5.7.1. __main__.__spec__ 5.8. Open issues 5.9. References 6. Expressions 6.1. Arithmetic conversions 6.2. Atoms 6.2.1. Identifiers (Names) 6.2.2. Literals 6.2.3. Parenthesized forms 6.2.4. Displays for lists, sets and dictionaries 6.2.5. List displays 6.2.6. Set displays 6.2.7. Dictionary displays 6.2.8. Generator expressions 6.2.9. Yield expressions 6.2.9.1. Generator-iterator methods 6.2.9.2. Examples 6.2.9.3. Asynchronous generator functions 6.2.9.4. Asynchronous generator-iterator methods 6.3. Primaries 6.3.1. Attribute references 6.3.2. Subscriptions 6.3.3. Slicings 6.3.4. Calls 6.4. Await expression 6.5. The power operator 6.6. Unary arithmetic and bitwise operations 6.7. Binary arithmetic operations 6.8. Shifting operations 6.9. Binary bitwise operations 6.10. Comparisons 6.10.1. Value comparisons 6.10.2. Membership test operations 6.10.3. Identity comparisons 6.11. Boolean operations 6.12. Conditional expressions 6.13. Lambdas 6.14. Expression lists 6.15. Evaluation order 6.16. Operator precedence 7. Simple statements 7.1. Expression statements 7.2. Assignment statements 7.2.1. Augmented assignment statements 7.2.2. Annotated assignment statements 7.3. The assert statement 7.4. The pass statement 7.5. The del statement 7.6. The return statement 7.7. The yield statement 7.8. The raise statement 7.9. The break statement 7.10. The continue statement 7.11. The import statement 7.11.1. Future statements 7.12. The global statement 7.13. The nonlocal statement 8. Compound statements 8.1. The if statement 8.2. The while statement 8.3. The for statement 8.4. The try statement 8.5. The with statement 8.6. Function definitions 8.7. Class definitions 8.8. Coroutines 8.8.1. Coroutine function definition 8.8.2. The async for statement 8.8.3. The async with statement 9. Top-level components 9.1. Complete Python programs 9.2. File input 9.3. Interactive input 9.4. Expression input 10. Full Grammar specification The Python Standard Library 1. Introduction 2. Built-in Functions 3. Built-in Constants 3.1. Constants added by the site module 4. Built-in Types 4.1. Truth Value Testing 4.2. Boolean Operations — and, or, not 4.3. Comparisons 4.4. Numeric Types — int, float, complex 4.4.1. Bitwise Operations on Integer Types 4.4.2. Additional Methods on Integer Types 4.4.3. Additional Methods on Float 4.4.4. Hashing of numeric types 4.5. Iterator Types 4.5.1. Generator Types 4.6. Sequence Types — list, tuple, range 4.6.1. Common Sequence Operations 4.6.2. Immutable Sequence Types 4.6.3. Mutable Sequence Types 4.6.4. Lists 4.6.5. Tuples 4.6.6. Ranges 4.7. Text Sequence Type — str 4.7.1. String Methods 4.7.2. printf-style String Formatting 4.8. Binary Sequence Types — bytes, bytearray, memoryview 4.8.1. Bytes Objects 4.8.2. Bytearray Objects 4.8.3. Bytes and Bytearray Operations 4.8.4. printf-style Bytes Formatting 4.8.5. Memory Views 4.9. Set Types — set, frozenset 4.10. Mapping Types — dict 4.10.1. Dictionary view objects 4.11. Context Manager Types 4.12. Other Built-in Types 4.12.1. Modules 4.12.2. Classes and Class Instances 4.12.3. Functions 4.12.4. Methods 4.12.5. Code Objects 4.12.6. Type Objects 4.12.7. The Null Object 4.12.8. The Ellipsis Object 4.12.9. The NotImplemented Object 4.12.10. Boolean Values 4.12.11. Internal Objects 4.13. Special Attributes 5. Built-in Exceptions 5.1. Base classes 5.2. Concrete exceptions 5.2.1. OS exceptions 5.3. Warnings 5.4. Exception hierarchy 6. Text Processing Services 6.1. string — Common string operations 6.1.1. String constants 6.1.2. Custom String Formatting 6.1.3. Format String Syntax 6.1.3.1. Format Specification Mini-Language 6.1.3.2. Format examples 6.1.4. Template strings 6.1.5. Helper functions 6.2. re — Regular expression operations 6.2.1. Regular Expression Syntax 6.2.2. Module Contents 6.2.3. Regular Expression Objects 6.2.4. Match Objects 6.2.5. Regular Expression Examples 6.2.5.1. Checking for a Pair 6.2.5.2. Simulating scanf() 6.2.5.3. search() vs. match() 6.2.5.4. Making a Phonebook 6.2.5.5. Text Munging 6.2.5.6. Finding all Adverbs 6.2.5.7. Finding all Adverbs and their Positions 6.2.5.8. Raw String Notation 6.2.5.9. Writing a Tokenizer 6.3. difflib — Helpers for computing deltas 6.3.1. SequenceMatcher Objects 6.3.2. SequenceMatcher Examples 6.3.3. Differ Objects 6.3.4. Differ Example 6.3.5. A command-line interface to difflib 6.4. textwrap — Text wrapping and filling 6.5. unicodedata — Unicode Database 6.6. stringprep — Internet String Preparation 6.7. readline — GNU readline interface 6.7.1. Init file 6.7.2. Line buffer 6.7.3. History file 6.7.4. History list 6.7.5. Startup hooks 6.7.6. Completion 6.7.7. Example 6.8. rlcompleter — Completion function for GNU readline 6.8.1. Completer Objects 7. Binary Data Services 7.1. struct — Interpret bytes as packed binary data 7.1.1. Functions and Exceptions 7.1.2. Format Strings 7.1.2.1. Byte Order, Size, and Alignment 7.1.2.2. Format Characters 7.1.2.3. Examples 7.1.3. Classes 7.2. codecs — Codec registry and base classes 7.2.1. Codec Base Classes 7.2.1.1. Error Handlers 7.2.1.2. Stateless Encoding and Decoding 7.2.1.3. Incremental Encoding and Decoding 7.2.1.3.1. IncrementalEncoder Objects 7.2.1.3.2. IncrementalDecoder Objects 7.2.1.4. Stream Encoding and Decoding 7.2.1.4.1. StreamWriter Objects 7.2.1.4.2. StreamReader Objects 7.2.1.4.3. StreamReaderWriter Objects 7.2.1.4.4. StreamRecoder Objects 7.2.2. Encodings and Unicode 7.2.3. Standard Encodings 7.2.4. Python Specific Encodings 7.2.4.1. Text Encodings 7.2.4.2. Binary Transforms 7.2.4.3. Text Transforms 7.2.5. encodings.idna — Internationalized Domain Names in Applications 7.2.6. encodings.mbcs — Windows ANSI codepage 7.2.7. encodings.utf_8_sig — UTF-8 codec with BOM signature 8. Data Types 8.1. datetime — Basic date and time types 8.1.1. Available Types 8.1.2. timedelta Objects 8.1.3. date Objects 8.1.4. datetime Objects 8.1.5. time Objects 8.1.6. tzinfo Objects 8.1.7. timezone Objects 8.1.8. strftime() and strptime() Behavior 8.2. calendar — General calendar-related functions 8.3. collections — Container datatypes 8.3.1. ChainMap objects 8.3.1.1. ChainMap Examples and Recipes 8.3.2. Counter objects 8.3.3. deque objects 8.3.3.1. deque Recipes 8.3.4. defaultdict objects 8.3.4.1. defaultdict Examples 8.3.5. namedtuple() Factory Function for Tuples with Named Fields 8.3.6. OrderedDict objects 8.3.6.1. OrderedDict Examples and Recipes 8.3.7. UserDict objects 8.3.8. UserList objects 8.3.9. UserString objects 8.4. collections.abc — Abstract Base Classes for Containers 8.4.1. Collections Abstract Base Classes 8.5. heapq — Heap queue algorithm 8.5.1. Basic Examples 8.5.2. Priority Queue Implementation Notes 8.5.3. Theory 8.6. bisect — Array bisection algorithm 8.6.1. Searching Sorted Lists 8.6.2. Other Examples 8.7. array — Efficient arrays of numeric values 8.8. weakref — Weak references 8.8.1. Weak Reference Objects 8.8.2. Example 8.8.3. Finalizer Objects 8.8.4. Comparing finalizers with __del__() methods 8.9. types — Dynamic type creation and names for built-in types 8.9.1. Dynamic Type Creation 8.9.2. Standard Interpreter Types 8.9.3. Additional Utility Classes and Functions 8.9.4. Coroutine Utility Functions 8.10. copy — Shallow and deep copy operations 8.11. pprint — Data pretty printer 8.11.1. PrettyPrinter Objects 8.11.2. Example 8.12. reprlib — Alternate repr() implementation 8.12.1. Repr Objects 8.12.2. Subclassing Repr Objects 8.13. enum — Support for enumerations 8.13.1. Module Contents 8.13.2. Creating an Enum 8.13.3. Programmatic access to enumeration members and their attributes 8.13.4. Duplicating enum members and values 8.13.5. Ensuring unique enumeration values 8.13.6. Using automatic values 8.13.7. Iteration 8.13.8. Comparisons 8.13.9. Allowed members and attributes of enumerations 8.13.10. Restricted subclassing of enumerations 8.13.11. Pickling 8.13.12. Functional API 8.13.13. Derived Enumerations 8.13.13.1. IntEnum 8.13.13.2. IntFlag 8.13.13.3. Flag 8.13.13.4. Others 8.13.14. Interesting examples 8.13.14.1. Omitting values 8.13.14.1.1. Using auto 8.13.14.1.2. Using object 8.13.14.1.3. Using a descriptive string 8.13.14.1.4. Using a custom __new__() 8.13.14.2. OrderedEnum 8.13.14.3. DuplicateFreeEnum 8.13.14.4. Planet 8.13.15. How are Enums different? 8.13.15.1. Enum Classes 8.13.15.2. Enum Members (aka instances) 8.13.15.3. Finer Points 8.13.15.3.1. Supported __dunder__ names 8.13.15.3.2. Supported _sunder_ names 8.13.15.3.3. Enum member type 8.13.15.3.4. Boolean value of Enum classes and members 8.13.15.3.5. Enum classes with methods 8.13.15.3.6. Combining members of Flag 9. Numeric and Mathematical Modules 9.1. numbers — Numeric abstract base classes 9.1.1. The numeric tower 9.1.2. Notes for type implementors 9.1.2.1. Adding More Numeric ABCs 9.1.2.2. Implementing the arithmetic operations 9.2. math — Mathematical functions 9.2.1. Number-theoretic and representation functions 9.2.2. Power and logarithmic functions 9.2.3. Trigonometric functions 9.2.4. Angular conversion 9.2.5. Hyperbolic functions 9.2.6. Special functions 9.2.7. Constants 9.3. cmath — Mathematical functions for complex numbers 9.3.1. Conversions to and from polar coordinates 9.3.2. Power and logarithmic functions 9.3.3. Trigonometric functions 9.3.4. Hyperbolic functions 9.3.5. Classification functions 9.3.6. Constants 9.4. decimal — Decimal fixed point and floating point arithmetic 9.4.1. Quick-start Tutorial 9.4.2. Decimal objects 9.4.2.1. Logical operands 9.4.3. Context objects 9.4.4. Constants 9.4.5. Rounding modes 9.4.6. Signals 9.4.7. Floating Point Notes 9.4.7.1. Mitigating round-off error with increased precision 9.4.7.2. Special values 9.4.8. Working with threads 9.4.9. Recipes 9.4.10. Decimal FAQ 9.5. fractions — Rational numbers 9.6. random — Generate pseudo-random numbers 9.6.1. Bookkeeping functions 9.6.2. Functions for integers 9.6.3. Functions for sequences 9.6.4. Real-valued distributions 9.6.5. Alternative Generator 9.6.6. Notes on Reproducibility 9.6.7. Examples and Recipes 9.7. statistics — Mathematical statistics functions 9.7.1. Averages and measures of central location 9.7.2. Measures of spread 9.7.3. Function details 9.7.4. Exceptions 10. Functional Programming Modules 10.1. itertools — Functions creating iterators for efficient looping 10.1.1. Itertool functions 10.1.2. Itertools Recipes 10.2. functools — Higher-order functions and operations on callable objects 10.2.1. partial Objects 10.3. operator — Standard operators as functions 10.3.1. Mapping Operators to Functions 10.3.2. Inplace Operators 11. File and Directory Access 11.1. pathlib — Object-oriented filesystem paths 11.1.1. Basic use 11.1.2. Pure paths 11.1.2.1. General properties 11.1.2.2. Operators 11.1.2.3. Accessing individual parts 11.1.2.4. Methods and properties 11.1.3. Concrete paths 11.1.3.1. Methods 11.2. os.path — Common pathname manipulations 11.3. fileinput — Iterate over lines from multiple input streams 11.4. stat — Interpreting stat() results 11.5. filecmp — File and Directory Comparisons 11.5.1. The dircmp class 11.6. tempfile — Generate temporary files and directories 11.6.1. Examples 11.6.2. Deprecated functions and variables 11.7. glob — Unix style pathname pattern expansion 11.8. fnmatch — Unix filename pattern matching 11.9. linecache — Random access to text lines 11.10. shutil — High-level file operations 11.10.1. Directory and files operations 11.10.1.1. copytree example 11.10.1.2. rmtree example 11.10.2. Archiving operations 11.10.2.1. Archiving example 11.10.3. Querying the size of the output terminal 11.11. macpath — Mac OS 9 path manipulation functions 12. Data Persistence 12.1. pickle — Python object serialization 12.1.1. Relationship to other Python modules 12.1.1.1. Comparison with marshal 12.1.1.2. Comparison with json 12.1.2. Data stream format 12.1.3. Module Interface 12.1.4. What can be pickled and unpickled? 12.1.5. Pickling Class Instances 12.1.5.1. Persistence of External Objects 12.1.5.2. Dispatch Tables 12.1.5.3. Handling Stateful Objects 12.1.6. Restricting Globals 12.1.7. Performance 12.1.8. Examples 12.2. copyreg — Register pickle support functions 12.2.1. Example 12.3. shelve — Python object persistence 12.3.1. Restrictions 12.3.2. Example 12.4. marshal — Internal Python object serialization 12.5. dbm — Interfaces to Unix “databases” 12.5.1. dbm.gnu — GNU’s reinterpretation of dbm 12.5.2. dbm.ndbm — Interface based on ndbm 12.5.3. dbm.dumb — Portable DBM implementation 12.6. sqlite3 — DB-API 2.0 interface for SQLite databases 12.6.1. Module functions and constants 12.6.2. Connection Objects 12.6.3. Cursor Objects 12.6.4. Row Objects 12.6.5. Exceptions 12.6.6. SQLite and Python types 12.6.6.1. Introduction 12.6.6.2. Using adapters to store additional Python types in SQLite databases 12.6.6.2.1. Letting your object adapt itself 12.6.6.2.2. Registering an adapter callable 12.6.6.3. Converting SQLite values to custom Python types 12.6.6.4. Default adapters and converters 12.6.7. Controlling Transactions 12.6.8. Using sqlite3 efficiently 12.6.8.1. Using shortcut methods 12.6.8.2. Accessing columns by name instead of by index 12.6.8.3. Using the connection as a context manager 12.6.9. Common issues 12.6.9.1. Multithreading 13. Data Compression and Archiving 13.1. zlib — Compression compatible with gzip 13.2. gzip — Support for gzip files 13.2.1. Examples of usage 13.3. bz2 — Support for bzip2 compression 13.3.1. (De)compression of files 13.3.2. Incremental (de)compression 13.3.3. One-shot (de)compression 13.4. lzma — Compression using the LZMA algorithm 13.4.1. Reading and writing compressed files 13.4.2. Compressing and decompressing data in memory 13.4.3. Miscellaneous 13.4.4. Specifying custom filter chains 13.4.5. Examples 13.5. zipfile — Work with ZIP archives 13.5.1. ZipFile Objects 13.5.2. PyZipFile Objects 13.5.3. ZipInfo Objects 13.5.4. Command-Line Interface 13.5.4.1. Command-line options 13.6. tarfile — Read and write tar archive files 13.6.1. TarFile Objects 13.6.2. TarInfo Objects 13.6.3. Command-Line Interface 13.6.3.1. Command-line options 13.6.4. Examples 13.6.5. Supported tar formats 13.6.6. Unicode issues 14. File Formats 14.1. csv — CSV File Reading and Writing 14.1.1. Module Contents 14.1.2. Dialects and Formatting Parameters 14.1.3. Reader Objects 14.1.4. Writer Objects 14.1.5. Examples 14.2. configparser — Configuration file parser 14.2.1. Quick Start 14.2.2. Supported Datatypes 14.2.3. Fallback Values 14.2.4. Supported INI File Structure 14.2.5. Interpolation of values 14.2.6. Mapping Protocol Access 14.2.7. Customizing Parser Behaviour 14.2.8. Legacy API Examples 14.2.9. ConfigParser Objects 14.2.10. RawConfigParser Objects 14.2.11. Exceptions 14.3. netrc — netrc file processing 14.3.1. netrc Objects 14.4. xdrlib — Encode and decode XDR data 14.4.1. Packer Objects 14.4.2. Unpacker Objects 14.4.3. Exceptions 14.5. plistlib — Generate and parse Mac OS X .plist files 14.5.1. Examples 15. Cryptographic Services 15.1. hashlib — Secure hashes and message digests 15.1.1. Hash algorithms 15.1.2. SHAKE variable length digests 15.1.3. Key derivation 15.1.4. BLAKE2 15.1.4.1. Creating hash objects 15.1.4.2. Constants 15.1.4.3. Examples 15.1.4.3.1. Simple hashing 15.1.4.3.2. Using different digest sizes 15.1.4.3.3. Keyed hashing 15.1.4.3.4. Randomized hashing 15.1.4.3.5. Personalization 15.1.4.3.6. Tree mode 15.1.4.4. Credits 15.2. hmac — Keyed-Hashing for Message Authentication 15.3. secrets — Generate secure random numbers for managing secrets 15.3.1. Random numbers 15.3.2. Generating tokens 15.3.2.1. How many bytes should tokens use? 15.3.3. Other functions 15.3.4. Recipes and best practices 16. Generic Operating System Services 16.1. os — Miscellaneous operating system interfaces 16.1.1. File Names, Command Line Arguments, and Environment Variables 16.1.2. Process Parameters 16.1.3. File Object Creation 16.1.4. File Descriptor Operations 16.1.4.1. Querying the size of a terminal 16.1.4.2. Inheritance of File Descriptors 16.1.5. Files and Directories 16.1.5.1. Linux extended attributes 16.1.6. Process Management 16.1.7. Interface to the scheduler 16.1.8. Miscellaneous System Information 16.1.9. Random numbers 16.2. io — Core tools for working with streams 16.2.1. Overview 16.2.1.1. Text I/O 16.2.1.2. Binary I/O 16.2.1.3. Raw I/O 16.2.2. High-level Module Interface 16.2.2.1. In-memory streams 16.2.3. Class hierarchy 16.2.3.1. I/O Base Classes 16.2.3.2. Raw File I/O 16.2.3.3. Buffered Streams 16.2.3.4. Text I/O 16.2.4. Performance 16.2.4.1. Binary I/O 16.2.4.2. Text I/O 16.2.4.3. Multi-threading 16.2.4.4. Reentrancy 16.3. time — Time access and conversions 16.3.1. Functions 16.3.2. Clock ID Constants 16.3.3. Timezone Constants 16.4. argparse — Parser for command-line options, arguments and sub-commands 16.4.1. Example 16.4.1.1. Creating a parser 16.4.1.2. Adding arguments 16.4.1.3. Parsing arguments 16.4.2. ArgumentParser objects 16.4.2.1. prog 16.4.2.2. usage 16.4.2.3. description 16.4.2.4. epilog 16.4.2.5. parents 16.4.2.6. formatter_class 16.4.2.7. prefix_chars 16.4.2.8. fromfile_prefix_chars 16.4.2.9. argument_default 16.4.2.10. allow_abbrev 16.4.2.11. conflict_handler 16.4.2.12. add_help 16.4.3. The add_argument() method 16.4.3.1. name or flags 16.4.3.2. action 16.4.3.3. nargs 16.4.3.4. const 16.4.3.5. default 16.4.3.6. type 16.4.3.7. choices 16.4.3.8. required 16.4.3.9. help 16.4.3.10. metavar 16.4.3.11. dest 16.4.3.12. Action classes 16.4.4. The parse_args() method 16.4.4.1. Option value syntax 16.4.4.2. Invalid arguments 16.4.4.3. Arguments containing - 16.4.4.4. Argument abbreviations (prefix matching) 16.4.4.5. Beyond sys.argv 16.4.4.6. The Namespace object 16.4.5. Other utilities 16.4.5.1. Sub-commands 16.4.5.2. FileType objects 16.4.5.3. Argument groups 16.4.5.4. Mutual exclusion 16.4.5.5. Parser defaults 16.4.5.6. Printing help 16.4.5.7. Partial parsing 16.4.5.8. Customizing file parsing 16.4.5.9. Exiting methods 16.4.6. Upgrading optparse code 16.5. getopt — C-style parser for command line options 16.6. logging — Logging facility for Python 16.6.1. Logger Objects 16.6.2. Logging Levels 16.6.3. Handler Objects 16.6.4. Formatter Objects 16.6.5. Filter Objects 16.6.6. LogRecord Objects 16.6.7. LogRecord attributes 16.6.8. LoggerAdapter Objects 16.6.9. Thread Safety 16.6.10. Module-Level Functions 16.6.11. Module-Level Attributes 16.6.12. Integration with the warnings module 16.7. logging.config — Logging configuration 16.7.1. Configuration functions 16.7.2. Configuration dictionary schema 16.7.2.1. Dictionary Schema Details 16.7.2.2. Incremental Configuration 16.7.2.3. Object connections 16.7.2.4. User-defined objects 16.7.2.5. Access to external objects 16.7.2.6. Access to internal objects 16.7.2.7. Import resolution and custom importers 16.7.3. Configuration file format 16.8. logging.handlers — Logging handlers 16.8.1. StreamHandler 16.8.2. FileHandler 16.8.3. NullHandler 16.8.4. WatchedFileHandler 16.8.5. BaseRotatingHandler 16.8.6. RotatingFileHandler 16.8.7. TimedRotatingFileHandler 16.8.8. SocketHandler 16.8.9. DatagramHandler 16.8.10. SysLogHandler 16.8.11. NTEventLogHandler 16.8.12. SMTPHandler 16.8.13. MemoryHandler 16.8.14. HTTPHandler 16.8.15. QueueHandler 16.8.16. QueueListener 16.9. getpass — Portable password input 16.10. curses — Terminal handling for character-cell displays 16.10.1. Functions 16.10.2. Window Objects 16.10.3. Constants 16.11. curses.textpad — Text input widget for curses programs 16.11.1. Textbox objects 16.12. curses.ascii — Utilities for ASCII characters 16.13. curses.panel — A panel stack extension for curses 16.13.1. Functions 16.13.2. Panel Objects 16.14. platform — Access to underlying platform’s identifying data 16.14.1. Cross Platform 16.14.2. Java Platform 16.14.3. Windows Platform 16.14.3.1. Win95/98 specific 16.14.4. Mac OS Platform 16.14.5. Unix Platforms 16.15. errno — Standard errno system symbols 16.16. ctypes — A foreign function library for Python 16.16.1. ctypes tutorial 16.16.1.1. Loading dynamic link libraries 16.16.1.2. Accessing functions from loaded dlls 16.16.1.3. Calling functions 16.16.1.4. Fundamental data types 16.16.1.5. Calling functions, continued 16.16.1.6. Calling functions with your own custom data types 16.16.1.7. Specifying the required argument types (function prototypes) 16.16.1.8. Return types 16.16.1.9. Passing pointers (or: passing parameters by reference) 16.16.1.10. Structures and unions 16.16.1.11. Structure/union alignment and byte order 16.16.1.12. Bit fields in structures and unions 16.16.1.13. Arrays 16.16.1.14. Pointers 16.16.1.15. Type conversions 16.16.1.16. Incomplete Types 16.16.1.17. Callback functions 16.16.1.18. Accessing values exported from dlls 16.16.1.19. Surprises 16.16.1.20. Variable-sized data types 16.16.2. ctypes reference 16.16.2.1. Finding shared libraries 16.16.2.2. Loading shared libraries 16.16.2.3. Foreign functions 16.16.2.4. Function prototypes 16.16.2.5. Utility functions 16.16.2.6. Data types 16.16.2.7. Fundamental data types 16.16.2.8. Structured data types 16.16.2.9. Arrays and pointers 17. Concurrent Execution 17.1. threading — Thread-based parallelism 17.1.1. Thread-Local Data 17.1.2. Thread Objects 17.1.3. Lock Objects 17.1.4. RLock Objects 17.1.5. Condition Objects 17.1.6. Semaphore Objects 17.1.6.1. Semaphore Example 17.1.7. Event Objects 17.1.8. Timer Objects 17.1.9. Barrier Objects 17.1.10. Using locks, conditions, and semaphores in the with statement 17.2. multiprocessing — Process-based parallelism 17.2.1. Introduction 17.2.1.1. The Process class 17.2.1.2. Contexts and start methods 17.2.1.3. Exchanging objects between processes 17.2.1.4. Synchronization between processes 17.2.1.5. Sharing state between processes 17.2.1.6. Using a pool of workers 17.2.2. Reference 17.2.2.1. Process and exceptions 17.2.2.2. Pipes and Queues 17.2.2.3. Miscellaneous 17.2.2.4. Connection Objects 17.2.2.5. Synchronization primitives 17.2.2.6. Shared ctypes Objects 17.2.2.6.1. The multiprocessing.sharedctypes module 17.2.2.7. Managers 17.2.2.7.1. Customized managers 17.2.2.7.2. Using a remote manager 17.2.2.8. Proxy Objects 17.2.2.8.1. Cleanup 17.2.2.9. Process Pools 17.2.2.10. Listeners and Clients 17.2.2.10.1. Address Formats 17.2.2.11. Authentication keys 17.2.2.12. Logging 17.2.2.13. The multiprocessing.dummy module 17.2.3. Programming guidelines 17.2.3.1. All start methods 17.2.3.2. The spawn and forkserver start methods 17.2.4. Examples 17.3. The concurrent package 17.4. concurrent.futures — Launching parallel tasks 17.4.1. Executor Objects 17.4.2. ThreadPoolExecutor 17.4.2.1. ThreadPoolExecutor Example 17.4.3. ProcessPoolExecutor 17.4.3.1. ProcessPoolExecutor Example 17.4.4. Future Objects 17.4.5. Module Functions 17.4.6. Exception classes 17.5. subprocess — Subprocess management 17.5.1. Using the subprocess Module 17.5.1.1. Frequently Used Arguments 17.5.1.2. Popen Constructor 17.5.1.3. Exceptions 17.5.2. Security Considerations 17.5.3. Popen Objects 17.5.4. Windows Popen Helpers 17.5.4.1. Constants 17.5.5. Older high-level API 17.5.6. Replacing Older Functions with the subprocess Module 17.5.6.1. Replacing /bin/sh shell backquote 17.5.6.2. Replacing shell pipeline 17.5.6.3. Replacing os.system() 17.5.6.4. Replacing the os.spawn family 17.5.6.5. Replacing os.popen(), os.popen2(), os.popen3() 17.5.6.6. Replacing functions from the popen2 module 17.5.7. Legacy Shell Invocation Functions 17.5.8. Notes 17.5.8.1. Converting an argument sequence to a string on Windows 17.6. sched — Event scheduler 17.6.1. Scheduler Objects 17.7. queue — A synchronized queue class 17.7.1. Queue Objects 17.8. dummy_threading — Drop-in replacement for the threading module 17.9. _thread — Low-level threading API 17.10. _dummy_thread — Drop-in replacement for the _thread module 18. Interprocess Communication and Networking 18.1. socket — Low-level networking interface 18.1.1. Socket families 18.1.2. Module contents 18.1.2.1. Exceptions 18.1.2.2. Constants 18.1.2.3. Functions 18.1.2.3.1. Creating sockets 18.1.2.3.2. Other functions 18.1.3. Socket Objects 18.1.4. Notes on socket timeouts 18.1.4.1. Timeouts and the connect method 18.1.4.2. Timeouts and the accept method 18.1.5. Example 18.2. ssl — TLS/SSL wrapper for socket objects 18.2.1. Functions, Constants, and Exceptions 18.2.1.1. Socket creation 18.2.1.2. Context creation 18.2.1.3. Random generation 18.2.1.4. Certificate handling 18.2.1.5. Constants 18.2.2. SSL Sockets 18.2.3. SSL Contexts 18.2.4. Certificates 18.2.4.1. Certificate chains 18.2.4.2. CA certificates 18.2.4.3. Combined key and certificate 18.2.4.4. Self-signed certificates 18.2.5. Examples 18.2.5.1. Testing for SSL support 18.2.5.2. Client-side operation 18.2.5.3. Server-side operation 18.2.6. Notes on non-blocking sockets 18.2.7. Memory BIO Support 18.2.8. SSL session 18.2.9. Security considerations 18.2.9.1. Best defaults 18.2.9.2. Manual settings 18.2.9.2.1. Verifying certificates 18.2.9.2.2. Protocol versions 18.2.9.2.3. Cipher selection 18.2.9.3. Multi-processing 18.2.10. LibreSSL support 18.3. select — Waiting for I/O completion 18.3.1. /dev/poll Polling Objects 18.3.2. Edge and Level Trigger Polling (epoll) Objects 18.3.3. Polling Objects 18.3.4. Kqueue Objects 18.3.5. Kevent Objects 18.4. selectors — High-level I/O multiplexing 18.4.1. Introduction 18.4.2. Classes 18.4.3. Examples 18.5. asyncio — Asynchronous I/O, event loop, coroutines and tasks 18.5.1. Base Event Loop 18.5.1.1. Run an event loop 18.5.1.2. Calls 18.5.1.3. Delayed calls 18.5.1.4. Futures 18.5.1.5. Tasks 18.5.1.6. Creating connections 18.5.1.7. Creating listening connections 18.5.1.8. Watch file descriptors 18.5.1.9. Low-level socket operations 18.5.1.10. Resolve host name 18.5.1.11. Connect pipes 18.5.1.12. UNIX signals 18.5.1.13. Executor 18.5.1.14. Error Handling API 18.5.1.15. Debug mode 18.5.1.16. Server 18.5.1.17. Handle 18.5.1.18. Event loop examples 18.5.1.18.1. Hello World with call_soon() 18.5.1.18.2. Display the current date with call_later() 18.5.1.18.3. Watch a file descriptor for read events 18.5.1.18.4. Set signal handlers for SIGINT and SIGTERM 18.5.2. Event loops 18.5.2.1. Event loop functions 18.5.2.2. Available event loops 18.5.2.3. Platform support 18.5.2.3.1. Windows 18.5.2.3.2. Mac OS X 18.5.2.4. Event loop policies and the default policy 18.5.2.5. Event loop policy interface 18.5.2.6. Access to the global loop policy 18.5.2.7. Customizing the event loop policy 18.5.3. Tasks and coroutines 18.5.3.1. Coroutines 18.5.3.1.1. Example: Hello World coroutine 18.5.3.1.2. Example: Coroutine displaying the current date 18.5.3.1.3. Example: Chain coroutines 18.5.3.2. InvalidStateError 18.5.3.3. TimeoutError 18.5.3.4. Future 18.5.3.4.1. Example: Future with run_until_complete() 18.5.3.4.2. Example: Future with run_forever() 18.5.3.5. Task 18.5.3.5.1. Example: Parallel execution of tasks 18.5.3.6. Task functions 18.5.4. Transports and protocols (callback based API) 18.5.4.1. Transports 18.5.4.1.1. BaseTransport 18.5.4.1.2. ReadTransport 18.5.4.1.3. WriteTransport 18.5.4.1.4. DatagramTransport 18.5.4.1.5. BaseSubprocessTransport 18.5.4.2. Protocols 18.5.4.2.1. Protocol classes 18.5.4.2.2. Connection callbacks 18.5.4.2.3. Streaming protocols 18.5.4.2.4. Datagram protocols 18.5.4.2.5. Flow control callbacks 18.5.4.2.6. Coroutines and protocols 18.5.4.3. Protocol examples 18.5.4.3.1. TCP echo client protocol 18.5.4.3.2. TCP echo server protocol 18.5.4.3.3. UDP echo client protocol 18.5.4.3.4. UDP echo server protocol 18.5.4.3.5. Register an open socket to wait for data using a protocol 18.5.5. Streams (coroutine based API) 18.5.5.1. Stream functions 18.5.5.2. StreamReader 18.5.5.3. StreamWriter 18.5.5.4. StreamReaderProtocol 18.5.5.5. IncompleteReadError 18.5.5.6. LimitOverrunError 18.5.5.7. Stream examples 18.5.5.7.1. TCP echo client using streams 18.5.5.7.2. TCP echo server using streams 18.5.5.7.3. Get HTTP headers 18.5.5.7.4. Register an open socket to wait for data using streams 18.5.6. Subprocess 18.5.6.1. Windows event loop 18.5.6.2. Create a subprocess: high-level API using Process 18.5.6.3. Create a subprocess: low-level API using subprocess.Popen 18.5.6.4. Constants 18.5.6.5. Process 18.5.6.6. Subprocess and threads 18.5.6.7. Subprocess examples 18.5.6.7.1. Subprocess using transport and protocol 18.5.6.7.2. Subprocess using streams 18.5.7. Synchronization primitives 18.5.7.1. Locks 18.5.7.1.1. Lock 18.5.7.1.2. Event 18.5.7.1.3. Condition 18.5.7.2. Semaphores 18.5.7.2.1. Semaphore 18.5.7.2.2. BoundedSemaphore 18.5.8. Queues 18.5.8.1. Queue 18.5.8.2. PriorityQueue 18.5.8.3. LifoQueue 18.5.8.3.1. Exceptions 18.5.9. Develop with asyncio 18.5.9.1. Debug mode of asyncio 18.5.9.2. Cancellation 18.5.9.3. Concurrency and multithreading 18.5.9.4. Handle blocking functions correctly 18.5.9.5. Logging 18.5.9.6. Detect coroutine objects never scheduled 18.5.9.7. Detect exceptions never consumed 18.5.9.8. Chain coroutines correctly 18.5.9.9. Pending task destroyed 18.5.9.10. Close transports and event loops 18.6. asyncore — Asynchronous socket handler 18.6.1. asyncore Example basic HTTP client 18.6.2. asyncore Example basic echo server 18.7. asynchat — Asynchronous socket command/response handler 18.7.1. asynchat Example 18.8. signal — Set handlers for asynchronous events 18.8.1. General rules 18.8.1.1. Execution of Python signal handlers 18.8.1.2. Signals and threads 18.8.2. Module contents 18.8.3. Example 18.9. mmap — Memory-mapped file support 19. Internet Data Handling 19.1. email — An email and MIME handling package 19.1.1. email.message: Representing an email message 19.1.2. email.parser: Parsing email messages 19.1.2.1. FeedParser API 19.1.2.2. Parser API 19.1.2.3. Additional notes 19.1.3. email.generator: Generating MIME documents 19.1.4. email.policy: Policy Objects 19.1.5. email.errors: Exception and Defect classes 19.1.6. email.headerregistry: Custom Header Objects 19.1.7. email.contentmanager: Managing MIME Content 19.1.7.1. Content Manager Instances 19.1.8. email: Examples 19.1.9. email.message.Message: Representing an email message using the compat32 API 19.1.10. email.mime: Creating email and MIME objects from scratch 19.1.11. email.header: Internationalized headers 19.1.12. email.charset: Representing character sets 19.1.13. email.encoders: Encoders 19.1.14. email.utils: Miscellaneous utilities 19.1.15. email.iterators: Iterators 19.2. json — JSON encoder and decoder 19.2.1. Basic Usage 19.2.2. Encoders and Decoders 19.2.3. Exceptions 19.2.4. Standard Compliance and Interoperability 19.2.4.1. Character Encodings 19.2.4.2. Infinite and NaN Number Values 19.2.4.3. Repeated Names Within an Object 19.2.4.4. Top-level Non-Object, Non-Array Values 19.2.4.5. Implementation Limitations 19.2.5. Command Line Interface 19.2.5.1. Command line options 19.3. mailcap — Mailcap file handling 19.4. mailbox — Manipulate mailboxes in various formats 19.4.1. Mailbox objects 19.4.1.1. Maildir 19.4.1.2. mbox 19.4.1.3. MH 19.4.1.4. Babyl 19.4.1.5. MMDF 19.4.2. Message objects 19.4.2.1. MaildirMessage 19.4.2.2. mboxMessage 19.4.2.3. MHMessage 19.4.2.4. BabylMessage 19.4.2.5. MMDFMessage 19.4.3. Exceptions 19.4.4. Examples 19.5. mimetypes — Map filenames to MIME types 19.5.1. MimeTypes Objects 19.6. base64 — Base16, Base32, Base64, Base85 Data Encodings 19.7. binhex — Encode and decode binhex4 files 19.7.1. Notes 19.8. binascii — Convert between binary and ASCII 19.9. quopri — Encode and decode MIME quoted-printable data 19.10. uu — Encode and decode uuencode files 20. Structured Markup Processing Tools 20.1. html — HyperText Markup Language support 20.2. html.parser — Simple HTML and XHTML parser 20.2.1. Example HTML Parser Application 20.2.2. HTMLParser Methods 20.2.3. Examples 20.3. html.entities — Definitions of HTML general entities 20.4. XML Processing Modules 20.4.1. XML vulnerabilities 20.4.2. The defusedxml and defusedexpat Packages 20.5. xml.etree.ElementTree — The ElementTree XML API 20.5.1. Tutorial 20.5.1.1. XML tree and elements 20.5.1.2. Parsing XML 20.5.1.3. Pull API for non-blocking parsing 20.5.1.4. Finding interesting elements 20.5.1.5. Modifying an XML File 20.5.1.6. Building XML documents 20.5.1.7. Parsing XML with Namespaces 20.5.1.8. Additional resources 20.5.2. XPath support 20.5.2.1. Example 20.5.2.2. Supported XPath syntax 20.5.3. Reference 20.5.3.1. Functions 20.5.3.2. Element Objects 20.5.3.3. ElementTree Objects 20.5.3.4. QName Objects 20.5.3.5. TreeBuilder Objects 20.5.3.6. XMLParser Objects 20.5.3.7. XMLPullParser Objects 20.5.3.8. Exceptions 20.6. xml.dom — The Document Object Model API 20.6.1. Module Contents 20.6.2. Objects in the DOM 20.6.2.1. DOMImplementation Objects 20.6.2.2. Node Objects 20.6.2.3. NodeList Objects 20.6.2.4. DocumentType Objects 20.6.2.5. Document Objects 20.6.2.6. Element Objects 20.6.2.7. Attr Objects 20.6.2.8. NamedNodeMap Objects 20.6.2.9. Comment Objects 20.6.2.10. Text and CDATASection Objects 20.6.2.11. ProcessingInstruction Objects 20.6.2.12. Exceptions 20.6.3. Conformance 20.6.3.1. Type Mapping 20.6.3.2. Accessor Methods 20.7. xml.dom.minidom — Minimal DOM implementation 20.7.1. DOM Objects 20.7.2. DOM Example 20.7.3. minidom and the DOM standard 20.8. xml.dom.pulldom — Support for building partial DOM trees 20.8.1. DOMEventStream Objects 20.9. xml.sax — Support for SAX2 parsers 20.9.1. SAXException Objects 20.10. xml.sax.handler — Base classes for SAX handlers 20.10.1. ContentHandler Objects 20.10.2. DTDHandler Objects 20.10.3. EntityResolver Objects 20.10.4. ErrorHandler Objects 20.11. xml.sax.saxutils — SAX Utilities 20.12. xml.sax.xmlreader — Interface for XML parsers 20.12.1. XMLReader Objects 20.12.2. IncrementalParser Objects 20.12.3. Locator Objects 20.12.4. InputSource Objects 20.12.5. The Attributes Interface 20.12.6. The AttributesNS Interface 20.13. xml.parsers.expat — Fast XML parsing using Expat 20.13.1. XMLParser Objects 20.13.2. ExpatError Exceptions 20.13.3. Example 20.13.4. Content Model Descriptions 20.13.5. Expat error constants 21. Internet Protocols and Support 21.1. webbrowser — Convenient Web-browser controller 21.1.1. Browser Controller Objects 21.2. cgi — Common Gateway Interface support 21.2.1. Introduction 21.2.2. Using the cgi module 21.2.3. Higher Level Interface 21.2.4. Functions 21.2.5. Caring about security 21.2.6. Installing your CGI script on a Unix system 21.2.7. Testing your CGI script 21.2.8. Debugging CGI scripts 21.2.9. Common problems and solutions 21.3. cgitb — Traceback manager for CGI scripts 21.4. wsgiref — WSGI Utilities and Reference Implementation 21.4.1. wsgiref.util – WSGI environment utilities 21.4.2. wsgiref.headers – WSGI response header tools 21.4.3. wsgiref.simple_server – a simple WSGI HTTP server 21.4.4. wsgiref.validate — WSGI conformance checker 21.4.5. wsgiref.handlers – server/gateway base classes 21.4.6. Examples 21.5. urllib — URL handling modules 21.6. urllib.request — Extensible library for opening URLs 21.6.1. Request Objects 21.6.2. OpenerDirector Objects 21.6.3. BaseHandler Objects 21.6.4. HTTPRedirectHandler Objects 21.6.5. HTTPCookieProcessor Objects 21.6.6. ProxyHandler Objects 21.6.7. HTTPPasswordMgr Objects 21.6.8. HTTPPasswordMgrWithPriorAuth Objects 21.6.9. AbstractBasicAuthHandler Objects 21.6.10. HTTPBasicAuthHandler Objects 21.6.11. ProxyBasicAuthHandler Objects 21.6.12. AbstractDigestAuthHandler Objects 21.6.13. HTTPDigestAuthHandler Objects 21.6.14. ProxyDigestAuthHandler Objects 21.6.15. HTTPHandler Objects 21.6.16. HTTPSHandler Objects 21.6.17. FileHandler Objects 21.6.18. DataHandler Objects 21.6.19. FTPHandler Objects 21.6.20. CacheFTPHandler Objects 21.6.21. UnknownHandler Objects 21.6.22. HTTPErrorProcessor Objects 21.6.23. Examples 21.6.24. Legacy interface 21.6.25. urllib.request Restrictions 21.7. urllib.response — Response classes used by urllib 21.8. urllib.parse — Parse URLs into components 21.8.1. URL Parsing 21.8.2. Parsing ASCII Encoded Bytes 21.8.3. Structured Parse Results 21.8.4. URL Quoting 21.9. urllib.error — Exception classes raised by urllib.request 21.10. urllib.robotparser — Parser for robots.txt 21.11. http — HTTP modules 21.11.1. HTTP status codes 21.12. http.client — HTTP protocol client 21.12.1. HTTPConnection Objects 21.12.2. HTTPResponse Objects 21.12.3. Examples 21.12.4. HTTPMessage Objects 21.13. ftplib — FTP protocol client 21.13.1. FTP Objects 21.13.2. FTP_TLS Objects 21.14. poplib — POP3 protocol client 21.14.1. POP3 Objects 21.14.2. POP3 Example 21.15. imaplib — IMAP4 protocol client 21.15.1. IMAP4 Objects 21.15.2. IMAP4 Example 21.16. nntplib — NNTP protocol client 21.16.1. NNTP Objects 21.16.1.1. Attributes 21.16.1.2. Methods 21.16.2. Utility functions 21.17. smtplib — SMTP protocol client 21.17.1. SMTP Objects 21.17.2. SMTP Example 21.18. smtpd — SMTP Server 21.18.1. SMTPServer Objects 21.18.2. DebuggingServer Objects 21.18.3. PureProxy Objects 21.18.4. MailmanProxy Objects 21.18.5. SMTPChannel Objects 21.19. telnetlib — Telnet client 21.19.1. Telnet Objects 21.19.2. Telnet Example 21.20. uuid — UUID objects according to RFC 4122 21.20.1. Example 21.21. socketserver — A framework for network servers 21.21.1. Server Creation Notes 21.21.2. Server Objects 21.21.3. Request Handler Objects 21.21.4. Examples 21.21.4.1. socketserver.TCPServer Example 21.21.4.2. socketserver.UDPServer Example 21.21.4.3. Asynchronous Mixins 21.22. http.server — HTTP servers 21.23. http.cookies — HTTP state management 21.23.1. Cookie Objects 21.23.2. Morsel Objects 21.23.3. Example 21.24. http.cookiejar — Cookie handling for HTTP clients 21.24.1. CookieJar and FileCookieJar Objects 21.24.2. FileCookieJar subclasses and co-operation with web browsers 21.24.3. CookiePolicy Objects 21.24.4. DefaultCookiePolicy Objects 21.24.5. Cookie Objec

PART I: CORE TECHNOLOGIES 1 Overview ...................................................................................................... 3 1.1 Introduction ...................................................................................................................... 3 1.2 Kernel Architecture ......................................................................................................... 3 1.3 Related Documentation Resources .............................................................................. 4 1.4 VxWorks Configuration and Build .............................................................................. 5 2 VxWorks Configuration ............................................................................. 7 2.1 Introduction ...................................................................................................................... 7 2.2 About VxWorks Configuration ................................................................................... 7 2.2.1 Default Configuration and Images ................................................................. 8 2.2.2 Configuration With VxWorks Image Projects ............................................... 8 2.2.3 Configuration With VxWorks Source Build Projects ................................... 8 2.2.4 Configuration and Customization .................................................................. 8 2.2.5 Configuration Tools: Workbench and vxprj .................................................. 9 2.3 VxWorks Image Projects: VIPs .................................................................................... 9 2.3.1 VxWorks Components ...................................................................................... 10 Component Names .......................................................................................... 10 Basic VxWorks Components ............................................................................ 11 2.3.2 Device Driver Selection ................................................................................... 13 2.3.3 Component Bundles and Configuration Profiles ........................................ 14 2.3.4 VxWorks Component Reference .................................................................... 14 2.4 VxWorks Source Build Projects: VSBs ....................................................................... 14 2.4.1 Basic Operating System VSB Options ........................................................... 16 BSP-Specific Optimizations ............................................................................. 16 VxWorks Kernel Programmer's Guide, 6.9 iv Inconsistent Cache Mode Support .................................................................. 17 System Viewer Instrumentation Support ...................................................... 17 Real-Time Process Support .............................................................................. 17 Object Management Support ........................................................................... 17 Error Detection and Reporting Policy Hooks ............................................... 18 Task Switch Hook Support .............................................................................. 18 Task Create Hook Support ............................................................................... 18 CPU Power Management Support ................................................................. 19 Advanced Options ............................................................................................ 19 VxWorks BSP Validation Test Suite Support ................................................. 19 Symmetric Multiprocessor (SMP) Support ................................................... 19 SMP Determinism ............................................................................................. 19 MIPC Support .................................................................................................... 20 WRLOAD Support ............................................................................................ 20 Task-Specific Current Working Directory ...................................................... 20 Device Name Length ........................................................................................ 20 NFS V3 Server Optimization ........................................................................... 20 DOSFS Name Length Compatible .................................................................. 21 2.4.2 VSB Profiles ........................................................................................................ 21 2.4.3 Using VSB Projects to Create VxWorks Systems: Basic Steps .................... 21 2.4.4 Developing Kernel Applications for VSB Systems ..................................... 21 2.5 VxWorks Without Networking ..................................................................................... 22 2.6 Small-Footprint VxWorks Configuration ................................................................... 22 2.6.1 About Small-Footprint VxWorks .................................................................... 22 Kernel Facilities ................................................................................................. 22 Unsupported Facilities ..................................................................................... 23 BSPs ..................................................................................................................... 23 2.6.2 Configuring Small Footprint VxWorks .......................................................... 23 Small-Footprint VSB Profile and Options ...................................................... 24 VSB Options Specific to the Small-Footprint Profile .................................... 24 Small-Footprint VIP Profile and Components .............................................. 25 Optional Components for a Small Footprint VIP Project ............................ 25 2.6.3 Configuration and Build Steps for Small-Footprint VxWorks ................... 25 2.6.4 Writing Applications for Small-Footprint VxWorks .................................... 26 2.6.5 Example Application ........................................................................................ 26 2.6.6 Debugging Small-Footprint VxWorks ............................................................ 28 2.7 VxWorks Image Types ................................................................................................... 28 2.7.1 Default VxWorks Images ................................................................................ 29 2.7.2 VxWorks Images for Development and Production Systems ..................... 29 2.7.3 Boot Parameter Configuration for Standalone VxWorks Images .............. 30 2.8 Image Size Considerations ............................................................................................ 30 2.8.1 Boot Loader and Downloadable Image ......................................................... 30 2.8.2 Self-Booting Image ............................................................................................ 31 Contents v 3 Boot Loader ................................................................................................. 33 3.1 Introduction ...................................................................................................................... 33 3.2 Using a Default Boot Loader ......................................................................................... 34 3.3 Boot Loader Image Types ............................................................................................... 35 3.4 Boot Loader Shell ............................................................................................................ 35 3.4.1 Boot Loader Shell Commands ......................................................................... 36 3.5 Boot Parameters ............................................................................................................... 39 3.5.1 Displaying Current Boot Parameters ............................................................. 40 3.5.2 Description of Boot Parameters ...................................................................... 41 3.5.3 Changing Boot Parameters Interactively ....................................................... 44 3.6 Rebooting VxWorks ........................................................................................................ 45 3.7 Configuring and Building Boot Loaders .................................................................... 46 3.7.1 Boot Loader Profiles .......................................................................................... 46 3.7.2 Boot Loader Components ................................................................................ 47 3.7.3 Configuring Boot Parameters Statically ......................................................... 47 3.7.4 Enabling Networking for Non-Boot Interfaces ............................................. 48 3.7.5 Selecting a Boot Device ..................................................................................... 48 3.7.6 Reconfiguring Boot Loader Memory Layout for 32-Bit VxWorks ............. 50 Redefining the Boot Loader Link Address for Custom Boot Loaders ....... 50 Reconfiguring Memory Layout for a Persistent Memory Region ............. 51 3.7.7 Reconfiguring Boot Loader Memory Layout for 64-Bit VxWorks ............. 53 3.7.8 Building Boot Loaders ...................................................................................... 53 3.8 Installing Boot Loaders .................................................................................................. 53 3.9 Booting From a Network ............................................................................................... 53 3.10 Booting From a Target File System ............................................................................. 55 3.11 Booting From the Host File System Using TSFS ..................................................... 55 4 Kernel Applications .................................................................................... 57 4.1 Introduction ...................................................................................................................... 57 4.2 About Kernel Applications ........................................................................................... 58 4.3 Comparing Kernel Applications with RTP Applications ....................................... 59 4.4 C and C++ Libraries ........................................................................................................ 60 VxWorks Kernel Programmer's Guide, 6.9 vi 4.5 Kernel Application Structure ........................................................................................ 60 4.6 VxWorks Header Files .................................................................................................... 61 4.6.1 VxWorks Header File: vxWorks.h ................................................................... 61 4.6.2 Other VxWorks Header Files ........................................................................... 62 4.6.3 ANSI Header Files ............................................................................................ 62 4.6.4 ANSI C++ Header Files .................................................................................... 62 4.6.5 The -I Compiler Flag ......................................................................................... 62 4.6.6 VxWorks Nested Header Files ........................................................................ 62 4.6.7 VxWorks Private Header Files ........................................................................ 63 4.7 Custom Header Files ....................................................................................................... 63 4.8 Static Instantiation of Kernel Objects ......................................................................... 64 4.8.1 About Static Instantiation of Kernel Objects ................................................. 64 Kernel Objects That can be Instantiated Statically ....................................... 65 Static Instantiation and Code Size .................................................................. 65 Advantages of Static Instantiation .................................................................. 65 Applications and Static Instantiation ............................................................. 66 4.8.2 Scope Of Static Declarations ............................................................................ 66 4.8.3 Caveat With Regard to Macro Use .................................................................. 66 4.8.4 Static Instantiation of Tasks ............................................................................. 66 4.8.5 Static Instantiation Of Semaphores ................................................................ 67 4.8.6 Static Instantiation of Message Queues ......................................................... 68 4.8.7 Static Instantiation of Watchdog Timers ........................................................ 68 4.9 Boot-Time Hook Routine Facility ............................................................................... 69 Boot-Time Hook Routine Stubs and Components ....................................... 69 Using Boot-Time Hook Routine Stubs ........................................................... 70 4.10 Kernel Applications and Kernel Component Requirements ................................. 71 4.11 Building Kernel Application Modules ....................................................................... 71 4.12 Downloading Kernel Application Object Modules to a Target ............................. 72 4.13 Linking Kernel Application Object Modules with VxWorks ................................ 72 4.14 Configuring VxWorks to Run Applications Automatically ................................... 72 5 C++ Development ....................................................................................... 75 5.1 Introduction ...................................................................................................................... 75 5.2 Configuring VxWorks for C++ ..................................................................................... 76 5.3 C++ Header Files ............................................................................................................. 76 Contents vii 5.4 Spawning Tasks That Use C++ ..................................................................................... 76 5.5 Calls Between C and C++ Code .................................................................................... 77 5.6 C++ Compiler Caveats .................................................................................................... 77 5.7 Using C++ in Signal Handlers and ISRs ................................................................... 78 5.8 Downloadable Kernel Modules in C++ ..................................................................... 78 5.9 C++ Compiler Differences ............................................................................................ 78 5.9.1 Template Instantiation ...................................................................................... 78 5.9.2 Run-Time Type Information ............................................................................ 80 5.10 Namespaces ...................................................................................................................... 80 5.11 C++ Exception Handling ................................................................................................ 81 5.12 Standard Template Library (STL) ................................................................................ 81 5.13 C++ Demo Example ........................................................................................................ 81 6 Multitasking ................................................................................................. 83 6.1 Introduction ...................................................................................................................... 83 6.2 About Tasks and Multitasking ..................................................................................... 84 6.2.1 Task States and Transitions .............................................................................. 85 Tasks States and State Symbols ....................................................................... 85 Illustration of Basic Task State Transitions .................................................... 86 6.3 VxWorks System Tasks .................................................................................................. 87 Basic VxWorks Tasks ......................................................................................... 88 Tasks for Optional Components ..................................................................... 91 6.4 Task Scheduling .............................................................................................................. 93 6.4.1 Task Priorities .................................................................................................... 93 6.4.2 VxWorks Traditional Scheduler ...................................................................... 93 Priority-Based Preemptive Scheduling .......................................................... 94 Scheduling and the Ready Queue ................................................................. 94 Round-Robin Scheduling ................................................................................. 95 6.5 Task Creation and Management ................................................................................... 97 6.5.1 Task Creation and Activation .......................................................................... 97 Static instantiation of Tasks ............................................................................. 98 6.5.2 Task Names and IDs ......................................................................................... 98 Task Naming Rules ........................................................................................... 99 Task Name and ID Routines ............................................................................ 99 VxWorks Kernel Programmer's Guide, 6.9 viii 6.5.3 Inter-Process Communication With Public Tasks ......................................... 99 6.5.4 Task Creation Options ...................................................................................... 100 6.5.5 Task Stack ........................................................................................................... 102 Task Stack Protection ........................................................................................ 102 6.5.6 Task Information ............................................................................................... 103 6.5.7 Task Deletion and Deletion Safety .................................................................. 104 6.5.8 Task Execution Control ..................................................................................... 105 6.5.9 Task Scheduling Control .................................................................................. 106 6.5.10 Tasking Extensions: Using Hook Routines .................................................... 107 6.6 Task Error Status: errno .................................................................................................. 108 6.6.1 Layered Definitions of errno ........................................................................... 109 6.6.2 A Separate errno Value for Each Task ............................................................ 109 6.6.3 Error Return Convention ................................................................................. 109 6.6.4 Assignment of Error Status Values ................................................................. 110 6.7 Task Exception Handling ............................................................................................... 110 6.8 Shared Code and Reentrancy ........................................................................................ 111 6.8.1 Dynamic Stack Variables .................................................................................. 112 6.8.2 Guarded Global and Static Variables ............................................................. 112 6.8.3 Task-Specific Variables .................................................................................... 113 Thread-Local Variables: __thread Storage Class ........................................... 113 taskVarLib and Task Variables ........................................................................ 114 6.8.4 Multiple Tasks with the Same Main Routine ................................................ 114 7 Intertask and Interprocess Communication ............................................. 117 7.1 Introduction ...................................................................................................................... 117 7.2 About Intertask and Interprocess Communication .................................................. 118 7.3 Shared Data Structures ................................................................................................... 119 7.4 Interrupt Locks ............................................................................................................... 120 7.5 Task Locks ........................................................................................................................ 121 7.6 Semaphores ...................................................................................................................... 122 7.6.1 Inter-Process Communication With Public Semaphores ............................. 123 7.6.2 Semaphore Creation and Use .......................................................................... 123 Options for Scalable and Inline Semaphore Routines ................................ 125 Static Instantiation of Semaphores ................................................................. 125 Scalable and Inline Semaphore Take and Give Routines ........................... 126 Contents ix 7.6.3 Binary Semaphores ........................................................................................... 126 Mutual Exclusion .............................................................................................. 127 Synchronization ................................................................................................. 128 7.6.4 Mutual-Exclusion Semaphores ....................................................................... 129 Priority Inversion and Priority Inheritance ................................................... 129 Deletion Safety ................................................................................................... 132 Recursive Resource Access .............................................................................. 133 7.6.5 Counting Semaphores ...................................................................................... 134 7.6.6 Read/Write Semaphores ................................................................................. 134 Specification of Read or Write Mode .............................................................. 135 Precedence for Write Access Operations ....................................................... 136 Read/Write Semaphores and System Performance ..................................... 136 7.6.7 Special Semaphore Options ............................................................................. 136 Semaphore Timeout .......................................................................................... 136 Semaphores and Queueing .............................................................................. 137 Semaphores and VxWorks Events .................................................................. 137 7.7 Message Queues .............................................................................................................. 137 7.7.1 Inter-Process Communication With Public Message Queues ..................... 138 7.7.2 Message Creation and Use ............................................................................... 138 Static Instantiation of Message Queues ......................................................... 139 Message Queue Timeout .................................................................................. 139 Message Queue Urgent Messages .................................................................. 140 Message Queues and Queuing Options ........................................................ 140 7.7.3 Displaying Message Queue Attributes .......................................................... 141 7.7.4 Servers and Clients with Message Queues .................................................... 141 7.7.5 Message Queues and VxWorks Events .......................................................... 142 7.8 Pipes ................................................................................................................................... 142 7.8.1 Creating Pipes ................................................................................................... 142 7.8.2 Writing to Pipes from ISRs ............................................................................... 142 7.8.3 I/O Control Functions ...................................................................................... 143 7.9 VxWorks Events ............................................................................................................... 143 7.9.1 Configuring VxWorks for Events .................................................................... 144 7.9.2 About Event Flags and the Task Events Register ......................................... 144 7.9.3 Receiving Events ............................................................................................... 145 7.9.4 Sending Events .................................................................................................. 146 7.9.5 Inter-Process Communication With Events .................................................. 148 7.9.6 Events Routines ................................................................................................. 148 7.9.7 Code Example ................................................................................................... 149 7.9.8 Show Routines and Events .............................................................................. 149 VxWorks Kernel Programmer's Guide, 6.9 x 7.10 Inter-Process Communication With Public Objects ................................................. 149 Creating and Naming Public and Private Objects ....................................... 150 Example of Inter-process Communication With a Public Semaphore ...... 150 7.11 About VxWorks API Timeout Parameters .................................................................. 152 7.12 About Object Ownership and Resource Reclamation ............................................. 152 8 Signals, ISRs, and Watchdog Timers ........................................................ 155 8.1 Introduction ...................................................................................................................... 155 8.2 Signals .............................................................................................................................. 156 8.2.1 Configuring VxWorks for Signals .................................................................. 157 8.2.2 Basic Signal Routines ........................................................................................ 158 8.2.3 Queued Signal Routines .................................................................................. 159 8.2.4 Signal Events ...................................................................................................... 162 8.2.5 Signal Handlers ................................................................................................. 163 8.3 Interrupt Service Routines: ISRs ................................................................................. 166 8.3.1 Configuring VxWorks for ISRs ........................................................................ 166 Configuring the Interrupt Stack ...................................................................... 166 Adding Show Routine Support ....................................................................... 167 8.3.2 Writing ISRs ....................................................................................................... 167 Restrictions on ISRs ........................................................................................... 167 Facilities Available for ISRs .............................................................................. 169 Reserving High Interrupt Levels .................................................................... 170 8.3.3 System Clock ISR Modification ....................................................................... 171 8.3.4 Connecting ISRs to Interrupts ......................................................................... 171 8.3.5 Getting Information About ISRs ..................................................................... 172 8.3.6 Debugging ISRs ................................................................................................. 173 8.4 Watchdog Timers ............................................................................................................. 174 Static Instantiation of Watchdog Timers ........................................................ 175 8.4.1 Inter-Process Communication With Public Watchdog Timers ................... 176 9 POSIX Facilities .......................................................................................... 177 9.1 Introduction ...................................................................................................................... 178 9.2 Configuring VxWorks with POSIX Facilities ............................................................ 179 9.2.1 VxWorks Components for POSIX Facilities .................................................. 179 9.3 General POSIX Support ................................................................................................. 180 9.4 POSIX Header Files ........................................................................................................ 181 Contents xi 9.5 POSIX Namespace .......................................................................................................... 183 9.6 POSIX Clocks and Timers ............................................................................................. 183 9.7 POSIX Asynchronous I/O .............................................................................................. 186 9.8 POSIX Advisory File Locking ....................................................................................... 186 9.9 POSIX Page-Locking Interface ..................................................................................... 186 9.10 POSIX Threads ................................................................................................................ 187 9.10.1 POSIX Thread Attributes ................................................................................. 188 9.10.2 VxWorks-Specific Pthread Attributes ............................................................ 188 9.10.3 Specifying Attributes when Creating Pthreads ........................................... 189 9.10.4 POSIX Thread Creation and Management .................................................... 190 9.10.5 POSIX Thread Attribute Access ...................................................................... 190 9.10.6 POSIX Thread Private Data ............................................................................. 191 9.10.7 POSIX Thread Cancellation ............................................................................. 192 9.11 POSIX Thread Mutexes and Condition Variables .................................................... 193 9.11.1 Thread Mutexes ................................................................................................. 193 Protocol Mutex Attribute ................................................................................ 194 Priority Ceiling Mutex Attribute .................................................................... 195 9.11.2 Condition Variables .......................................................................................... 195 9.12 POSIX and VxWorks Scheduling ................................................................................. 196 9.12.1 Differences in POSIX and VxWorks Scheduling ........................................... 197 9.12.2 POSIX and VxWorks Priority Numbering ..................................................... 198 9.12.3 Default Scheduling Policy ................................................................................ 198 9.12.4 VxWorks Traditional Scheduler ...................................................................... 198 9.12.5 POSIX Threads Scheduler ................................................................................ 199 9.12.6 POSIX Scheduling Routines ............................................................................ 203 9.12.7 Getting Scheduling Parameters: Priority Limits and Time Slice ................ 204 9.13 POSIX Semaphores ......................................................................................................... 204 9.13.1 Comparison of POSIX and VxWorks Semaphores ....................................... 205 9.13.2 Using Unnamed Semaphores .......................................................................... 206 9.13.3 Using Named Semaphores .............................................................................. 208 9.14 POSIX Message Queues ................................................................................................. 211 9.14.1 Comparison of POSIX and VxWorks Message Queues ............................... 212 9.14.2 POSIX Message Queue Attributes .................................................................. 213 9.14.3 Displaying Message Queue Attributes .......................................................... 214 VxWorks Kernel Programmer's Guide, 6.9 xii 9.14.4 Communicating Through a Message Queue ................................................ 215 9.14.5 Notification of Message Arrival ..................................................................... 218 9.15 POSIX Signals .................................................................................................................. 222 9.16 POSIX Memory Management ....................................................................................... 222 10 Memory Management ................................................................................. 223 10.1 Introduction ...................................................................................................................... 223 10.2 32-Bit VxWorks Memory Layout ................................................................................. 224 10.2.1 Displaying Information About Memory Layout .......................................... 224 10.2.2 System Memory Map Without RTP Support ................................................ 224 10.2.3 System Memory Map with RTP Support ....................................................... 226 10.2.4 System RAM Autosizing .................................................................................. 228 10.2.5 Reserved Memory: User-Reserved Memory and Persistent Memory ...... 228 10.3 64-Bit VxWorks Memory Layout ................................................................................. 229 10.3.1 Displaying Information About Memory Layout .......................................... 230 10.3.2 Virtual Memory Regions .................................................................................. 230 Kernel System Virtual Memory Region ......................................................... 231 Kernel Virtual Memory Pool Region .............................................................. 232 Kernel Reserved Memory Region ................................................................... 232 Shared User Virtual Memory Region ............................................................. 232 RTP Private Virtual Memory Region .............................................................. 232 10.3.3 Global RAM Pool .............................................................................................. 233 10.3.4 Kernel Memory Map ........................................................................................ 233 Kernel System Memory .................................................................................... 235 Kernel Common Heap ...................................................................................... 235 DMA32 Heap ..................................................................................................... 235 User-Reserved Memory ................................................................................... 235 Persistent Memory ............................................................................................ 235 10.3.5 Reserved Memory Configuration: User-Reserved Memory and Persistent Memory .............................................................................................................. 236 10.3.6 System RAM Autosizing .................................................................................. 236 10.4 About VxWorks Memory Allocation Facilities ......................................................... 236 10.5 32-Bit VxWorks Heap and Memory Partition Management .................................. 237 10.5.1 Configuring the Kernel Heap and the Memory Partition Manager .......... 238 10.5.2 Basic Heap and Memory Partition Manager ................................................. 238 10.5.3 Full Heap and Memory Partition Manager ................................................... 238 10.6 64-Bit VxWorks Heap and Memory Partition Management .................................. 239 10.6.1 Kernel Common Heap ...................................................................................... 239 Contents xiii 10.6.2 Kernel Proximity Heap ..................................................................................... 240 10.6.3 DMA32 Heap ..................................................................................................... 240 10.7 SMP-Optimized Memory Allocation .......................................................................... 241 10.7.1 Configuration ..................................................................................................... 241 10.7.2 Usage scenarios ................................................................................................. 241 10.8 Memory Pools .................................................................................................................. 242 10.9 POSIX Memory Management ....................................................................................... 242 10.9.1 POSIX Memory Management APIs ................................................................ 243 10.9.2 POSIX Memory Mapping ................................................................................ 244 10.9.3 POSIX Memory Protection ............................................................................... 244 10.9.4 POSIX Memory Locking .................................................................................. 244 10.10 Memory Mapping Facilities .......................................................................................... 245 10.10.1 POSIX Memory-Mapped Files ........................................................................ 247 10.10.2 POSIX Shared Memory Objects ...................................................................... 247 10.10.3 Anonymous Memory Mapping ...................................................................... 247 10.10.4 Device Memory Objects ................................................................................... 248 10.10.5 Shared Data Regions ......................................................................................... 249 10.11 Virtual Memory Management ..................................................................................... 249 10.11.1 Configuring Virtual Memory Management .................................................. 250 10.11.2 Managing Virtual Memory Programmatically ............................................. 251 Modifying Page States ...................................................................................... 252 Making Memory Non-Writable ...................................................................... 253 Invalidating Memory Pages ............................................................................ 255 Locking TLB Entries .......................................................................................... 255 Page Size Optimization .................................................................................... 255 Setting Page States in ISRs ............................................................................... 256 10.11.3 Troubleshooting ................................................................................................. 256 10.12 Additional Memory Protection Features ................................................................... 257 10.12.1 Configuring VxWorks for Additional Memory Protection ......................... 257 10.12.2 Stack Overrun and Underrun Detection ........................................................ 258 10.12.3 Non-Executable Task Stack .............................................................................. 258 10.12.4 Text Segment Write Protection ........................................................................ 258 10.12.5 Exception Vector Table Write Protection ........................................................ 259 10.13 Memory Error Detection ................................................................................................ 259 10.13.1 Heap and Partition Memory Instrumentation .............................................. 259 10.13.2 Compiler Instrumentation: 32-Bit VxWorks .................................................. 264 VxWorks Kernel Programmer's Guide, 6.9 xiv 11 I/O System ................................................................................................... 269 11.1 Introduction ...................................................................................................................... 269 11.2 About the VxWorks I/O System ................................................................................... 270 Differences Between VxWorks and Host System I/O ................................. 270 11.3 Configuring VxWorks With I/O Facilities .................................................................. 271 11.4 I/O Devices, Named Files, and File Systems ............................................................ 272 11.5 Remote File System Access From VxWorks ............................................................... 273 NFS File System Access from VxWorks ......................................................... 273 Non-NFS Network File System Access from VxWorks WIth FTP or RSH 273 11.6 Basic I/O ............................................................................................................................ 275 11.6.1 File Descriptors .................................................................................................. 275 File Descriptor Table ......................................................................................... 276 11.6.2 Standard Input, Standard Output, and Standard Error .............................. 276 11.6.3 Standard I/O Redirection ................................................................................ 276 Issues with Standard I/O Redirection ........................................................... 277 11.6.4 Open and Close ................................................................................................. 278 11.6.5 Create and Remove ........................................................................................... 280 11.6.6 Read and Write .................................................................................................. 281 11.6.7 File Truncation ................................................................................................... 281 11.6.8 I/O Control ........................................................................................................ 282 11.6.9 Pending on Multiple File Descriptors with select( ) ..................................... 282 11.6.10 POSIX File System Routines ............................................................................ 284 11.7 Standard I/O ..................................................................................................................... 285 11.7.1 Configuring VxWorks With Standard I/O .................................................... 285 11.7.2 About printf( ), sprintf( ), and scanf( ) ............................................................ 286 11.7.3 About Standard I/O and Buffering ................................................................ 286 11.7.4 About Standard Input, Standard Output, and Standard Error .................. 287 11.8 Other Formatted I/O ....................................................................................................... 287 11.8.1 Output in Serial I/O Polled Mode: kprintf( ) ................................................ 287 Writing to User-Defined Storage Media With kprintf( ) and kputs( ) ....... 288 11.8.2 Additional Formatted I/O Routines ............................................................. 289 11.8.3 Message Logging ............................................................................................... 289 11.9 Asynchronous Input/Output ......................................................................................... 289 11.9.1 The POSIX AIO Routines ................................................................................. 290 Contents xv 11.9.2 AIO Control Block ............................................................................................. 291 11.9.3 Using AIO ........................................................................................................... 292 AIO with Periodic Checks for Completion ................................................... 292 Alternatives for Testing AIO Completion ..................................................... 294 12 Devices ........................................................................................................ 297 12.1 Introduction ...................................................................................................................... 297 12.2 About Devices in VxWorks ........................................................................................... 298 12.3 Serial I/O Devices: Terminal and Pseudo-Terminal Devices .................................. 299 tty Options .......................................................................................................... 299 12.3.1 Raw Mode and Line Mode .............................................................................. 300 12.3.2 tty Special Characters ....................................................................................... 300 12.3.3 I/O Control Functions ...................................................................................... 301 12.4 Pipe Devices ..................................................................................................................... 302 12.5 Pseudo I/O Device ........................................................................................................... 302 12.5.1 I/O Control Functions ...................................................................................... 303 12.6 Null Devices .................................................................................................................... 303 12.7 Block Devices ................................................................................................................... 303 12.7.1 XBD RAM Disk .................................................................................................. 305 12.7.2 SCSI Drivers ....................................................................................................... 306 Configuring SCSI Drivers ................................................................................ 306 Structure of the SCSI Subsystem ..................................................................... 307 Booting and Initialization ................................................................................ 308 Device-Specific Configuration Options ......................................................... 308 SCSI Configuration Examples ......................................................................... 310 Troubleshooting ................................................................................................. 312 12.8 Extended Block Device Facility: XBD ......................................................................... 313 12.8.1 XBD Disk Partition Manager ........................................................................... 313 12.8.2 XBD Block Device Wrapper ............................................................................. 314 12.8.3 XBD TRFS Component ..................................................................................... 314 12.9 PCMCIA ............................................................................................................................ 315 12.10 Peripheral Component Interconnect: PCI .................................................................. 315 12.11 Network File System (NFS) Devices ........................................................................... 315 12.11.1 I/O Control Functions for NFS Clients .......................................................... 316 12.12 Non-NFS Network Devices ........................................................................................... 317 VxWorks Kernel Programmer's Guide, 6.9 xvi 12.12.1 Creating Network Devices ............................................................................... 318 12.12.2 I/O Control Functions ...................................................................................... 318 12.13 Sockets ............................................................................................................................... 318 12.14 Internal I/O System Structure ....................................................................................... 319 12.14.1 Drivers ................................................................................................................ 321 The Driver Table and Installing Drivers ........................................................ 322 Example of Installing a Driver ........................................................................ 322 12.14.2 Devices ................................................................................................................ 323 The Device List and Adding Devices ............................................................. 323 Example of Adding Devices ............................................................................ 324 Deleting Devices ................................................................................................ 324 12.14.3 File Descriptors .................................................................................................. 327 File Descriptor Table ......................................................................................... 327 Example of Opening a File ............................................................................... 327 Example of Reading Data from the File ......................................................... 330 Example of Closing a File ................................................................................. 331 Implementing select( ) ...................................................................................... 331 Cache Coherency ............................................................................................... 334 13 Local File Systems ..................................................................................... 339 13.1 Introduction ...................................................................................................................... 339 13.2 File System Monitor ...................................................................................................... 341 Device Insertion Events .................................................................................... 342 XBD Name Mapping Facility .......................................................................... 343 13.3 Virtual Root File System: VRFS ................................................................................... 343 13.4 Highly Reliable File System: HRFS ............................................................................ 345 13.4.1 Configuring VxWorks for HRFS ..................................................................... 345 13.4.2 Configuring HRFS ............................................................................................ 346 13.4.3 Creating an HRFS File System ....................................................................... 347 Overview of HRFS File System Creation ....................................................... 347 HRFS File System Creation Steps ................................................................... 347 13.4.4 HRFS, ATA, and RAM Disk Examples .......................................................... 348 13.4.5 Optimizing HRFS Performance ...................................................................... 353 13.4.6 Transactional Operations and Commit Policies ......................................... 353 Automatic Commit Policy ............................................................................... 353 High-Speed Commit Policy ............................................................................. 354 Mandatory Commits ......................................................................................... 354 Rollbacks ............................................................................................................. 354 Programmatically Initiating Commits ........................................................... 354 13.4.7 File Access Time Stamps .................................................................................. 355 Contents xvii 13.4.8 Maximum Number of Files and Directories ................................................. 355 13.4.9 Working with Directories ................................................................................. 355 Creating Subdirectories .................................................................................... 355 Removing Subdirectories ................................................................................. 356 Reading Directory Entries ................................................................................ 356 13.4.10 Working with Files ............................................................................................ 356 File I/O Routines ............................................................................................... 356 File Linking and Unlinking ............................................................................. 356 File Permissions ................................................................................................. 357 13.4.11 I/O Control Functions Supported by HRFS ................................................. 357 13.4.12 Crash Recovery and Volume Consistency ..................................................... 358 Crash Recovery .................................................................................................. 358 Consistency Checking ...................................................................................... 358 13.4.13 File Management and Full Devices ................................................................ 358 13.5 MS-DOS-Compatible File System: dosFs .................................................................. 359 13.5.1 Configuring VxWorks for dosFs ..................................................................... 360 13.5.2 Configuring dosFs ............................................................................................ 361 13.5.3 Creating a dosFs File System ........................................................................... 362 Overview of dosFs File System Creation ....................................................... 362 dosFs File System Creation Steps ................................................................... 363 13.5.4 dosFs, ATA Disk, and RAM Disk Examples ................................................. 365 13.5.5 Optimizing dosFs Performance ...................................................................... 369 13.5.6 Working with Volumes and Disks .................................................................. 370 Accessing Volume Configuration Information ............................................. 370 Synchronizing Volumes .................................................................................... 370 13.5.7 Working with Directories ................................................................................. 370 Creating Subdirectories .................................................................................... 370 Removing Subdirectories ................................................................................. 371 Reading Directory Entries ................................................................................ 371 13.5.8 Working with Files ............................................................................................ 371 File I/O Routines ............................................................................................... 371 File Attributes .................................................................................................... 371 13.5.9 Disk Space Allocation Options ........................................................................ 373 Choosing an Allocation Method ..................................................................... 374 Using Cluster Group Allocation ..................................................................... 374 Using Absolutely Contiguous Allocation ...................................................... 374 13.5.10 Crash Recovery and Volume Consistency ..................................................... 376 13.5.11 I/O Control Functions Supported by dosFsLib ............................................ 376 13.5.12 Booting from a Local dosFs File System Using SCSI ................................... 378 13.6 Transaction-Based Reliable File System Support for dosFs: TRFS ....................... 380 VxWorks Kernel Programmer's Guide, 6.9 xviii 13.6.1 Configuring VxWorks With TRFS ................................................................... 380 13.6.2 Automatic Instantiation of TRFS .................................................................... 380 13.6.3 Formatting a Device for TRFS ......................................................................... 381 13.6.4 Using TRFS in Applications ............................................................................ 382 TRFS Code Examples ....................................................................................... 382 13.7 Raw File System: rawFs ................................................................................................. 383 13.7.1 Configuring VxWorks for rawFs ..................................................................... 383 13.7.2 Creating a rawFs File System .......................................................................... 383 13.7.3 Mounting rawFs Volumes ................................................................................ 384 13.7.4 rawFs File I/O ................................................................................................... 385 13.7.5 I/O Control Functions Supported by rawFsLib ........................................... 385 13.8 CD-ROM File System: cdromFs ................................................................................... 386 13.8.1 Configuring VxWorks for cdromFs ................................................................ 387 13.8.2 Creating and Using cdromFs ........................................................................... 387 13.8.3 I/O Control Functions Supported by cdromFsLib ...................................... 389 13.8.4 Version Numbers ............................................................................................... 390 13.9 Read-Only Memory File System: ROMFS ................................................................. 390 13.9.1 Configuring VxWorks with ROMFS ............................................................... 391 13.9.2 Adding a ROMFS Directory and File Content to VxWorks ........................ 391 13.9.3 Accessing Files in ROMFS ............................................................................... 392 13.9.4 Using ROMFS to Start Applications Automatically .................................... 392 13.10 Target Server File System: TSFS ................................................................................... 392 Socket Support ................................................................................................... 393 Error Handling .................................................................................................. 394 Configuring VxWorks for TSFS Use ............................................................... 394 Security Considerations ................................................................................... 394 Using the TSFS to Boot a Target ...................................................................... 395 14 Flash File System Support: TrueFFS ........................................................ 397 14.1 Introduction ...................................................................................................................... 397 14.2 Overview of Implementation Steps ............................................................................ 398 14.3 Creating a VxWorks System with TrueFFS ................................................................ 400 14.3.1 Selecting an MTD .............................................................................................. 400 14.3.2 Identifying the Socket Driver .......................................................................... 400 14.3.3 Configuring VxWorks with TrueFFS and File System ................................. 401 Including the Core TrueFFS Component ....................................................... 401 Including the MTD Component ...................................................................... 402 Contents xix Including the Translation Layer Component ................................................ 402 Including the Socket Driver ............................................................................. 403 Including the XBD Wrapper Component ...................................................... 403 Including File System Components ............................................................... 403 Including Utility Components ........................................................................ 403 14.3.4 Building the System .......................................................................................... 404 14.3.5 Formatting the Flash ......................................................................................... 404 Formatting With sysTffsFormat( ) .................................................................. 404 Formatting With tffsDevFormat( ) .................................................................. 405 14.3.6 Reserving a Region in Flash for a Boot Image .............................................. 406 Reserving a Fallow Region .............................................................................. 407 Writing the Boot Image to Flash ...................................................................... 408 14.3.7 Mounting the Drive .......................................................................................... 409 14.3.8 Creating a File System ...................................................................................... 409 14.3.9 Testing the Drive ............................................................................................... 410 14.4 Using TrueFFS Shell Commands ................................................................................. 410 14.5 Using TrueFFS With HRFS ............................................................................................

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