c++ - 删除数组

Question

让我们假设以下代码:

    int* ptr = new int[10];
    ...
    ...
    ptr += 2;
    delete[] ptr;
    ptr = NULL;

调用 delete 时 ptr 应该指向数组的第一个元素吗？

Answer 1

如果您对未从 new 返回的内容调用 delete，则为未定义行为。

所以下面代码的结果是未定义的:

int* ptr = new int[10];
ptr += 2;
delete[] ptr;

我们也来看看标准:

C++ 2011. Section 3.7.4.2 Deallocation functions. Paragraph 3.

Otherwise, the behavior is undefined if the value supplied to operator delete(void*) in the standard library is not one of the values returned by a previous invocation of either operator new(std::size_t) or operator new(std::size_t, const std::nothrow_t&) in the standard library, and the behavior is undefined if the value supplied to operator delete[](void*) in the standard library is not one of the values returned by a previous invocation of either operator new[](std::size_t) or operator new[](std::size_t, const std::nothrow_t&) in the standard library.