使用new和without实例化对象之间的区别 [英] What is difference between instantiating an object using new vs. without

问题描述

在C ++中，

除了动态内存分配之外，以下两行代码之间存在功能差异：

Aside from dynamic memory allocation, is there a functional difference between the following two lines of code:

Time t (12, 0, 0); //t is a Time object

Time* t = new Time(12, 0, 0);//t is a pointer to a dynamically allocated Time object

我假设已经定义了一个Time（int，int，int）ctor。我也意识到，在第二种情况下，t将需要被删除，因为它是在堆上分配。是否有其他差异？

I am assuming of course that a Time(int, int, int) ctor has been defined. I also realize that in the second case t will need to be deleted as it was allocated on the heap. Is there any other difference?

推荐答案

行：

Time t (12, 0, 0);

...分配类型的变量

... allocates a variable of type Time in local scope, generally on the stack, which will be destroyed when its scope ends.

相比之下，

Time* t = new Time(12, 0, 0);

...通过调用 :: operator new （）或 Time :: operator new（），然后调用 Time :: Time（）与这设置为该内存块中的地址（也作为 new 的结果返回）然后存储在 t 中。如你所知，这是一般在堆上完成（默认情况下），并要求你删除它稍后在程序中， t 是一般存储在堆栈中。

... allocates a block of memory by calling either ::operator new() or Time::operator new(), and subsequently calls Time::Time() with this set to an address within that memory block (and also returned as the result of new), which is then stored in t. As you know, this is generally done on the heap (by default) and requires that you delete it later in the program, while the pointer in t is generally stored on the stack.

这篇关于使用new和without实例化对象之间的区别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！