如何用C ++中的新操作符初始化内存？ [英] How to initialise memory with new operator in C++?

问题描述

我刚刚开始进入C ++，我想学习一些好的习惯。如果我刚刚为 new 运算符分配了 int 类型的数组，那么如何将它们全部初始化为0循环通过他们自己？我应该使用 memset 吗？是否有C ++

I'm just beginning to get into C++ and I want to pick up some good habits. If I have just allocated an array of type int with the new operator, how can I initialise them all to 0 without looping through them all myself? Should I just use memset? Is there a “C++” way to do it?

推荐答案

这是一个令人惊讶的C ++的一个鲜为人知的特性（证据表明，没有人给定这是一个答案），但它实际上具有特殊的语法默认初始化数组（好吧，技术上，它被称为价值初始化在标准）：

It's a surprisingly little-known feature of C++ (as evidenced by the fact that no-one has given this as an answer yet), but it actually has special syntax for default-initializing an array (well, technically, it's called "value-initialize" in the Standard):

new int[10]();

请注意，您必须使用空括号，使用（0）或任何其他表达式（这是为什么这只有用于默认初始化）。

Note that you must use the empty parentheses - you cannot, for example, use (0) or any other expression (which is why this is only useful for default initialization).

这是ISO C ++ 03明确允许的5.3.4 [expr.new] / 15，它说：

This is explicitly permitted by ISO C++03 5.3.4[expr.new]/15, which says:

创建类型为T的对象的new-expression按如下方式初始化该对象：

A new-expression that creates an object of type T initializes that object as follows:

...

• 如果new-initializer是形式（），则该项目是值初始化（8.5）;




• If the new-initializer is of the form (), the item is value-initialized (8.5);

，并不限制允许使用的类型，而（expression-list）表单明确限制在同一节中的其他规则，因此它不允许数组类型。

and does not restrict the types for which this is allowed, whereas the (expression-list) form is explicitly restricted by further rules in the same section such that it does not allow array types.

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