新汽车会做什么? [英] What does `new auto` do?

问题描述

使用new auto是什么意思?考虑以下表达式:

What does it mean when I use new auto? Consider the expression:

new auto(5)

动态分配的对象是什么类型?它返回的指针是什么类型?

What is the type of the dynamically allocated object? What is the type of the pointer it returns?

推荐答案

在这种情况下，auto(5)解析为int(5).

In this context, auto(5) resolves to int(5).

您正在从堆中分配一个新的int，并将其初始化为5.

You are allocating a new int from the heap, initialized to 5.

(因此，它返回一个int *)

在得到许可的情况下引用安迪·普罗的足智多谋的答案:

Quoting Andy Prowl's resourceful answer, with permission:

根据C ++ 11标准的5.3.4/2段:

Per Paragraph 5.3.4/2 of the C++11 Standard:

如果auto类型说明符出现在 new-type-id 或 type-id 的 type-specifier-seq 中> new-expression ， new-expression 应包含形式为

new-initializer

If the auto type-specifier appears in the type-specifier-seq of a new-type-id or type-id of a new-expression, the new-expression shall contain a new-initializer of the form

( assignment-expression )

分配的类型是从new-initializer推导出的，如下所示:假设e是 assignment-expression new-initializer 和T是 new-expression 的 new-type-id 或 type-id ，则分配的类型就是该类型 在发明的声明(7.1.6.4)中为变量x推论得出:

The allocated type is deduced from the new-initializer as follows: Let e be the assignment-expression in the new-initializer and T be the new-type-id or type-id of the new-expression, then the allocated type is the type deduced for the variable x in the invented declaration (7.1.6.4):

T x(e);

[示例:

new auto(1); // allocated type is int
auto x = new auto(’a’); // allocated type is char, x is of type char*

— 示例]

这篇关于新汽车会做什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！