c++ - C++中new int()和new int {}的区别

Question

我知道 new int() 和 new int(10) 之间的区别。在第一种情况下，0 被分配，在第二种情况下，10 被分配给新创建的 int。但是 new int{} 之间是什么？我们使用 {} 进行数组初始化，例如 new a[]{4,5,6}。但是对于单个变量，在初始化时使用大括号是什么意思？

/* Combined usage and initialized to 0*/
    int *ptr2 = new int();
    cout<<"*ptr2 = "<<*ptr2<<endl;

    /* Allocated memory can be initialized to specific value */
    int*ptr3 = new int(5);
    cout<<"*ptr3 = "<<*ptr3<<endl;

    int* ptr5 = new int{500};
    cout<<"*ptr5 = "<<*ptr5<<endl;

Answer 1

你的输出是这样的:

*ptr2 =  0 

*ptr3 =  5 

*ptr5 =  500 

你的情况没有区别。

但总的来说:

( expression-list )     (1)     
= expression            (2)     
{ initializer-list }    (3) 

1) comma-separated list of arbitrary expressions and braced-init-lists in parentheses

2) the equals sign followed by an expression

3) braced-init-list: possibly empty, comma-separated list of expressions and other braced-init-lists

引用:http://en.cppreference.com/w/cpp/language/initialization