c++ - `new auto` 有什么作用？

Question

当我使用 new auto 是什么意思？考虑表达式:

new auto(5)

动态分配对象的类型是什么？它返回的指针是什么类型的？

Answer 1

在这种情况下，auto(5) 解析为 int(5)。

您正在从堆中分配一个新的 int，初始化为 5。

(所以，它返回一个 int *)

经许可引用 Andy Prowl 的足智多谋的回答:

根据 C++11 标准的第 5.3.4/2 段:

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 )

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);

[ Example:

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

—end example ]