为什么我们甚至需要"delete []"操作员? [英] Why do we even need the "delete[]" operator?

问题描述

这是一个困扰我一段时间的问题.我一直认为应该设计C ++，以便即使使用"new []"运算符也可以使用"delete"运算符(不带括号).

This is a question that's been nagging me for some time. I always thought that C++ should have been designed so that the "delete" operator (without brackets) works even with the "new[]" operator.

我认为是这样写的:

int* p = new int;

应该等效于分配一个包含1个元素的数组:

should be equivalent to allocating an array of 1 element:

int* p = new int[1];

如果是这样，则"delete"运算符始终可以删除数组，而我们不需要"delete []"运算符.

If this was true, the "delete" operator could always be deleting arrays, and we wouldn't need the "delete[]" operator.

在C ++中引入"delete []"运算符有什么理由吗?我能想到的唯一原因是分配数组的内存占用很小(您必须将数组大小存储在某个地方)，因此区分删除"与删除[]"是一个小的内存优化.

Is there any reason why the "delete[]" operator was introduced in C++? The only reason I can think of is that allocating arrays has a small memory footprint (you have to store the array size somewhere), so that distinguishing "delete" vs "delete[]" was a small memory optimization.

推荐答案

这样可以调用各个元素的析构函数.是的，对于POD数组没有太大区别，但是在C ++中，您可以拥有带有非平凡析构函数的对象数组.

It's so that the destructors of the individual elements will be called. Yes, for arrays of PODs, there isn't much of a difference, but in C++, you can have arrays of objects with non-trivial destructors.

现在，您的问题是，为什么不让new和delete表现得像new[]和delete[]并摆脱new[]和delete[]?我回头看看Stroustrup的设计与演化"一书，他在书中说，如果您不使用C ++功能，则不必为它们付费(至少在运行时).按照现在的样子，new或delete的行为将与malloc和free一样有效.如果delete具有delete[]的含义，那么在运行时将有一些额外的开销(如James Curran所指出的那样).

Now, your question is, why not make new and delete behave like new[] and delete[] and get rid of new[] and delete[]? I would go back Stroustrup's "Design and Evolution" book where he said that if you don't use C++ features, you shouldn't have to pay for them (at run time at least). The way it stands now, a new or delete will behave as efficiently as malloc and free. If delete had the delete[] meaning, there would be some extra overhead at run time (as James Curran pointed out).

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