. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 25.13Accessing Data through a Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 25.14线程安全 . . . . . . . . considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220 Address Sanitizer (ASAN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1220 "1" julia> pointer.([s1, s2], 1) 106 CHAPTER 11. 变量作用域 2-element Array{Ptr{UInt8},1}: Ptr{UInt8} @0x00000000132c9638 Ptr{UInt8} @0x0000000013dd3d18 julia> s1 = s2 "1" julia> pointer.([s1, s2], 1)

discriminant type takes 2 bytes, because 10001 fits 2 bytes. 探索更多 Rust 具有多种优化措施，可以减少枚举占用的空间。 • Null pointer optimization: For some types, Rust guarantees that size_of::() equals size_of::>(). • static is similar to mutable global variables in C++. • static provides object identity: an address in memory and state as required by types with interior mutability such as Mutex. 探索更多 Because Let's write a simple recursive evaluator for arithmetic expressions. The Box type here is a smart pointer, and will be covered in detail later in the course. An expression can be ”boxed” with Box::new as

其它运算数必须是长字符串。 • + 运算符的返回结果和任何字符串类型是兼容的。但是，若运算数都是短字符串或字符，并且 它们的组合长度大于 255，则返回结果取前面的 255 个字符。 Pointer operators（指针运算符） 关系运算符 <、>、<= 和 >= 能对 PChar 类型进行操作（参考关系运算符）。下面的运算符也能使 用指针类型作为运算数。关于指针的更多信息，请参考指针和指针类型。 字符指针，整数 P - Q ^ pointer dereference 指针 指针的基础类型 P^ = 等于 指针 布尔 P = Q <> 不等于 指针 布尔 P <> Q ^ 运算符 dereference 一个指针（取得指针所指的内容，如何翻译呢？），除了通用指针 Pointer 以 外，它的运算数可以是任何指针类型，对于 Pointer 类型，在 dereference 是一个过程类型的变量时有特殊的规则，请参考语 句和表达式中的过程类型）。若默认的编译器指示字 {$T–} 在起作用，则@X 的类型是 Pointer（通用指针）；在 {$T+} 状态下时，@X 的类型是 ^T，这里 T 是 X 的类型； • 若 F 是一个例程（一个函数或过程），@F 返回 F 的入口点，@F 的类型总是 Pointer； • 当 @ 作用于类的方法时，必须使用类名来限定方法名。比如 @TMyClass.DoSomething

中的 string 类型。 Go 的内存管理机制无法管理通过 C 代码分配的内存。 开发人员需要通过手动调用 C.free 来释放变量的内存： defer C.free(unsafe.Pointer(Cvariable)) 这一行最好紧跟在使用 C 代码创建某个变量之后，这样就不会忘记释放内存了。下面的代码展示了如何使 用 cgo 创建变量、使用并释放其内存： 示例 3.3 c2.go import "C" import "unsafe" func Print(s string) { cs := C.CString(s) defer C.free(unsafe.Pointer(cs)) C.fputs(cs, (*C.FILE)(C.stdout)) } 构建 cgo 包 你可以在使用将会在第 9.5 节讲到的 Makefile 文件（因为我们使用了一个独立的包），除了使用变量 用十六进制数表示，如： 0x6b0820 或 0xf84001d7f0 。 Go 语言的取地址符是 & ，放到一个变量前使用就会返回相应变量的内存地址。 下面的代码片段（示例 4.9 pointer.go）可能输出 An integer: 5, its location in memory: 0x6b0820 （这个值随着你每次运行程序而变化）。 var i1 = 5 fmt.Printf("An

string 类型。 Go 的内存管理机制无法管理通过 C 代码分配的内存。 开发人员需要通过手动调用 C.free 来释放变量的内存： 1. defer C.free(unsafe.Pointer(Cvariable)) 这一行最好紧跟在使用 C 代码创建某个变量之后，这样就不会忘记释放内存了。下面的代码展示了如何使用 cgo 创 建变量、使用并释放其内存： 示例 3.3 c2.go "unsafe" 7. 8. func Print(s string) { 9. cs := C.CString(s) 10. defer C.free(unsafe.Pointer(cs)) 11. C.fputs(cs, (*C.FILE)(C.stdout)) 12. } 构建 cgo 包 你可以在使用将会在第 9.5 节讲到的 Makefile 文件 制数表示，如： 0x6b0820 或 0xf84001d7f0 。 Go 语言的取地址符是 & ，放到一个变量前使用就会返回相应变量的内存地址。 下面的代码片段（示例 4.9 pointer.go）可能输出 An integer: 5, its location in memory: 0x6b0820 （这个值随 着你每次运行程序而变化）。 1. var i1 = 5 2

be moved to map large memory blocks quickly. Pointer authentication codes (PACs): The register value is authenticated before being used as a pointer to access the data or code, so as to defend against Shared Virtual Addressing (SVA): It allows host processes and devices to use the same virtual address, avoiding the need for replicating resources between hosts and devices. SVA improves service fully utilized. The new file system, EulerFS, is equipped with metadata soft update technology. Its pointer-based directory and dual-view counting mechanism reduces metadata synchronization overheads to

place of Require group .... Access control In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and platforms. The NameVirtualHost directive no longer has any effect, other than to emit a warning. Any address/port combination appearing in multiple virtual hosts is implicitly treated as a name-based virtual proxies for mod_proxy mod_remoteip Replaces the apparent client remote IP address and hostname for the request with the IP address list presented by a proxies or a load balancer via the request headers.

place of Require group .... Access control In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and platforms. The NameVirtualHost directive no longer has any effect, other than to emit a warning. Any address/port combination appearing in multiple virtual hosts is implicitly treated as a name-based virtual proxies for mod_proxy mod_remoteip Replaces the apparent client remote IP address and hostname for the request with the IP address list presented by a proxies or a load balancer via the request headers.

place of Require group .... Access control In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and platforms. The NameVirtualHost directive no longer has any effect, other than to emit a warning. Any address/port combination appearing in multiple virtual hosts is implicitly treated as a name-based virtual proxies for mod_proxy mod_remoteip Replaces the apparent client remote IP address and hostname for the request with the IP address list presented by a proxies or a load balancer via the request headers.

place of Require group .... Access control In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and platforms. The NameVirtualHost directive no longer has any effect, other than to emit a warning. Any address/port combination appearing in multiple virtual hosts is implicitly treated as a name-based virtual proxies for mod_proxy mod_remoteip Replaces the apparent client remote IP address and hostname for the request with the IP address list presented by a proxies or a load balancer via the request headers.