August 2021
Intermediate to advanced
450 pages
9h 36m
Chinese
Content preview from C++程序设计：原理与实践（基础篇）（原书第2版）
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12.4 自由空间和指针
思考一下12.2节结尾的vector实现。vector从哪里获得它的元素的空间？我们如何令指针elem指向它们？当你开始编写一个C++程序时，编译器为你的代码分配内存（有时称为代码存储（code storage）或文本存储（text storage）），并为你定义的全局变量分配内存（称为静态存储（static storage））。编译器还会为你预留调用函数时所需的空间，函数需要用这些空间保存其参数和局部变量（称为栈存储（stack storage）或自动存储（automatic storage））。计算机中的剩余内存可用于其他用途；它是“自由的”（“空闲的”）。这种内存分配方式可图示如下：
C++语言用称为new的运算符将“自由空间”（free store，又称为堆（heap））变为可用状态。例如：
这段代码要求C++运行时系统在自由空间中分配四个double，并将指向第一个double的指针返回给我们。我们使用此指针来初始化指针变量p。可图示如下：
运算符new返回一个指向它创建的对象的指针。如果它创建了多个对象（一个数组），它返回指向第一个对象的指针。如果对象的类型是X，则new返回的指针类型是X*。例如： ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.