在使用new（c ++）的构造函数调用中不使用括号 [英] Not using parentheses in constructor call with new (c++)

问题描述

可能重复：

$ b

$ b

所以我在我的主要：

  pC = new Class; 
  

它的工作方式为

  Class * pC = new Class（）; 
  

我今天意识到我已经省略了括号（所以我被

解决问题。

方案

如果类定义了默认构造函数，那么两者都是等效的;该对象将通过调用该构造函数创建。

如果类只有一个隐式的默认构造函数，那么就有区别。第一个将使任何POD类型的成员未初始化;第二个值将初始化它们（即将它们设置为零）。

Possible Duplicate:
Do the parentheses after the type name make a difference with new?

So I had in my main:

Class* pC = new Class;

It was working as

Class* pC = new Class();

I realized just today that I had omitted the parentheses (so I was hit by the "opposite" of the most vexing parse in a way).

My question: Are these two forms equivalent ?

解决方案

If the class has a default constructor defined, then both are equivalent; the object will be created by calling that constructor.

If the class only has an implicit default constructor, then there is a difference. The first will leave any members of POD type uninitialised; the second will value-initialise them (i.e. set them to zero).

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