什么是c ++中的新的返回类型？ [英] what is return type of new in c++?

问题描述

在C中， malloc（）返回 void * 。但在C ++中， new 会返回什么？

in C, malloc() returns void*. But in C++, what does new return?

double d = new int;

推荐答案

一个是 新表达式 。它是表达式 new T ，其结果是 T * 。它做两件事：首先，它调用 new运算符来分配内存，然后它调用T.的构造函数

There's two things you have to distinguish. One is a new expression. It is the expression new T and its result is a T*. It does two things: First, it calls the new operator to allocate memory, then it invokes the constructor for T. (If the constructor aborts with an exception, it will also call the delete operator.)

上述 新运算符 / strong>，但是，有几种口味。最突出的是这一个：

The aforementioned new operator, however, comes in several flavours. The most prominent is this one:

void* operator new(std::size_t);

你可以明确地调用它，但是这很少做。

You could call it explicitly, but that's rarely ever done.

还有其他形式的 new运算符，例如数组

There are other forms of the new operator, for example for arrays

void* operator new[](std::size_t);

或所谓的 placement new new，因为它不分配）：

or the so-called placement new (which really is a fake-new, since it doesn't allocate):

void* operator new(void*, std::size_t);

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