C++ 是否支持变长数组?

问题描述

不，等等，忍受我...

No, wait, bear with me...

VLA 一直是 GCC 的扩展，但它们被 C99 采用:

VLAs were always a GCC extension, but they were adopted by C99:

[C99: 6.7.5.2/4]: 如果大小不存在，则数组类型为不完整的类型.如果大小是 * 而不是表达式，则数组类型是未指定大小的可变长度数组类型，它只能在具有函数原型作用域的声明中使用；这样的数组仍然是完整的类型.如果大小为整数常量表达式并且元素类型具有已知的常量大小，数组类型不是变长数组类型；否则，数组类型是变长数组类型.

[C99: 6.7.5.2/4]: If the size is not present, the array type is an incomplete type. If the size is * instead of being an expression, the array type is a variable length array type of unspecified size, which can only be used in declarations with function prototype scope; such arrays are nonetheless complete types. If the size is an integer constant expression and the element type has a known constant size, the array type is not a variable length array type; otherwise, the array type is a variable length array type.

C99 也称为 ISO/IEC 9899:1999.

现在:

[C++11: 1.1/2]: C++ 是一种基于通用编程语言使用 ISO/IEC 9899:1999 中规定的 C 编程语言(以下简称C标准).除了C 提供的工具，C++ 提供额外的数据类型、类、模板、异常、命名空间、运算符重载、函数名超载、引用、免费的商店管理操作符，以及额外的图书馆设施.

[C++11: 1.1/2]: C++ is a general purpose programming language based on the C programming language as specified in ISO/IEC 9899:1999 (hereinafter referred to as the C standard). In addition to the facilities provided by C, C++ provides additional data types, classes, templates, exceptions, namespaces, operator overloading, function name overloading, references, free store management operators, and additional library facilities.

那么 C++11 不应该也有 VLA 吗?

推荐答案

这种留有余地的措辞并不意味着 C99 中的所有内容都在 C++11 中.您引用的只是介绍性文字.

That leeway wording doesn't mean that any and everything in C99 is in C++11. What you quoted is just introductory text.

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