删除和删除[]删除数组时是否相同？ [英] Delete and delete [] are the same when deleting arrays?

问题描述

可能的重复项：

如何将new []与delete配对可能会导致内存泄漏？

（POD）释放内存：是delete []等于删除吗？

使用gcc版本4.1.2 20080704（Red Hat 4.1.2-48）。没有在Visual C ++上测试它。

Using gcc version 4.1.2 20080704 (Red Hat 4.1.2-48). Haven't tested it on Visual C++.

似乎 delete 和 delete [] 删除简单类型的数组时也是如此。

It seems that delete and delete [] works the same when deleting arrays of "simple" type.

char * a = new char[1024];
delete [] a; // the correct way. no memory leak.

char * a = new char[1024];
delete a; // the incorrect way. also NO memory leak.

But, when deleting arrays of "complex" type, delete will cause memory leak.

class A
{
public:
    int m1;
    int* m2; // a pointer!
    A()
    {
        m2 = new int[1024];
    }
    ~A()
    {
        delete [] m2; // destructor won't be called when using delete
    }
};
A* a = new A[1024];
delete [] a; // the correct way. no memory leak.

A* a = new A[1024];
delete a; // the incorrect way. MEMORY LEAK!!!

我的问题是：

1. 在第一个测试用例中，为什么 delete 和 delete [] / li>
   
2. 在第二个测试用例中，为什么g ++不像第一个测试用例那样处理它呢？

1. In the first test case, why delete and delete [] are the same under g++?
2. In the second test case, why g++ doesn't handle it like the first test case?

推荐答案

这完全取决于底层的内存管理器。简单来说，C ++要求您使用 delete [] 删除数组，并使用 delete 删除非数组。

This is all dependent on the underlying memory manager. Simply put, C++ requires that you delete arrays with delete[] and delete non-arrays with delete. There is no explanation in the standard for your behaviour.

然而，可能发生的是 delete p; 从 p 开始的内存块（无论是否为数组）。另一方面， delete [] 另外运行数组的每个元素，并调用析构函数。由于 char 的正常数据类型没有析构函数，因此没有效果，因此 delete 和 delete [] 最后做同样的事情。

What's likely happening however is that delete p; simply frees the block of memory starting at p (whether it is an array or not). On the other hand delete[] additionally runs through each element of the array and calls the destructor. Since normal data types like char don't have destructors, there is no effect, so delete and delete[] end up doing the same thing.

就像我说的，不能保证 delete 将适用于任何类型的数组。它只是碰巧在你的情况下工作。在C ++中，我们称之为未定义的行为 - 它可能工作，它可能不会，它可能做一些完全随机和意想不到的事情。你最好避免依赖未定义的行为。

Like I said, this is all implementation specific. There's no guarantee that delete will work on arrays of any type. It just happens to work in your case. In C++ we call this undefined behaviour -- it might work, it might not, it might do something totally random and unexpected. You'd be best to avoid relying on undefined behaviour.

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