Malloc函数在C ++中 [英] Malloc function in C++

问题描述

我从C过渡到C ++。在C ++中，malloc函数有什么用处吗？或者我可以使用new关键字声明它。例如：

  class Node 
 {
 ... 
} 
 ... 
 Node * node1 = malloc（sizeof（Node））; // malloc 
 Node * node2 = new Node; // new 
  

我应该使用哪一个？

解决方案

使用 new 。你不应该在C ++程序中使用 malloc ，除非它与某些C代码交互，或者你有某种原因以特殊方式管理内存。

您的 node = malloc（sizeof（Node））的示例是一个坏主意，因为 Node （如果存在）不会被调用，并且后续的删除节点将具有未定义的结果。

如果你需要一个字节缓冲区，而不是一个对象，你通常会这样做：

  char * buffer = new char [1024]; 
  

或者，最好是这样：

  std :: vector< char>缓冲器（1024）; 
  

请注意，对于第二个示例（使用 std :: vector< ），不需要 delete 对象;它的内存将在超出范围时自动释放。你应该努力避免在C ++程序中使用 new 和 malloc ，而是使用自动管理自己内存的对象。 / p>

I am transitioning to C++ from C. In C++, is there any use for the malloc function? Or can I just declare it with the "new" keyword. For example:

class Node
{
    ...
}
...
Node *node1 = malloc(sizeof(Node));        //malloc
Node *node2 = new Node;                    //new

Which one should I use?

解决方案

Use new. You shouldn't need to use malloc in a C++ program, unless it is interacting with some C code or you have some reason to manage memory in a special way.

Your example of node = malloc(sizeof(Node)) is a bad idea, because the constructor of Node (if any exists) would not be called, and a subsequent delete node; would have undefined results.

If you need a buffer of bytes, rather than an object, you'll generally want to do something like this:

char *buffer = new char[1024];

or, preferably, something like this:

std::vector<char> buffer(1024);

Note that for the second example (using std::vector<>), there is no need to delete the object; its memory will automatically be freed when it goes out of scope. You should strive to avoid both new and malloc in C++ programs, instead using objects that automatically manage their own memory.

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