从头开始编写 heapify 函数，得到 "stack-based buffer overrun"

Question

我是第一次尝试实现堆排序算法，但是我在使用 heapify 函数时遇到错误。

Unhandled exception at 0x0005369A in heapify.exe: Stack cookie instrumentation code detected a stack-based buffer overrun.

控制台打开，输出为999 10 5 11 1012398875 2 0 1。

有人可以帮助我了解这里出了什么问题吗？谢谢。

#include <iostream>

// given the address of element 0 of an array, and a non-zero index k, heapify assumes that the L/R subtrees
// of node k are max heaps. But the subtrees combined with node k do not necesarily form 
// a max heap. heapify interchanges the value at node k with the value of one of its children,
// and then calls itself on the subtree in question 
int heapify(int* n, int k, int sizeOfHeap)
{
    // terminate the function if the input "node" is not actually a node
    if (k > sizeOfHeap)
    {
        return 0;
    }
        int root = *(n + k); // value of kth node
        int leftChild = *(n + 2 * k); // value of left chold
        int rightChild = *(n + 2 * k + 1); // value of right child
        if (root < leftChild)
        {
            // swap value of kth node with value of its left child
            int temp = root;
            *(n + k) = leftChild;
            *(n + 2 * k) = root;

            // call heapify on the left child
            heapify(n, 2 * k, sizeOfHeap);
        }
        else
        {
            // swap value of kth node with value of its right child
            int temp = root;
            *(n + k) = rightChild;
            *(n + 2 * k + 1) = root;

            // call heapify on right child
            heapify(n, 2 * k + 1, sizeOfHeap);
        }
    
}

int main()
{
    // arr is the array we will heapify. 999 is just a placeholder. 
    // The actual (almost) heap occupies indices 1 - 7
    int arr[8] = {999, 3, 10, 11, 5, 2, 0, 1};
    int sizeOfHeap = 8;
    
    heapify(arr, 1, sizeOfHeap);

    // print out arr
    int i;
    for (i = 0; i <= 7; i++)
    {
        std::cout << arr[i] << std::endl;
    }
}

Answer 1

Unhandled exception at 0x0005369A in heapify.exe: Stack cookie instrumentation code detected a stack-based buffer overrun.

The console does open, and the output is 999 10 5 11 1012398875 2 0 1.

Could someone help me understand what is going wrong here? Thank you.

Stack of process (one of real-live uses of stack data structure, FILO queue)是内存中静态分配的地方。对于所有流程，始终很小且几乎相同。在堆栈上，编译器仍然保存局部变量，即小的静态分配缓冲区（发生这种情况然后堆栈指针在 Linux 上移动以扩展堆栈大小，并且编译器评估堆栈上的偏移量）。它们（缓冲区）无法正确处理（不安全的库函数，如 strcpy()) so they could be potentially overflowed (overrunned) leading to buffer overflow 漏洞。

Stack cookie AKA stack canary 是一种缓解技术，用于在攻击者尝试利用 stack buffer overflow 之类的漏洞时将顺序数据写入堆栈，但不限于（如果您从堆返回堆的堆栈枢轴但严重覆盖保存的指令指针...没关系 ;))。如果检测到溢出，则它们会引发 SegFault。 Example link with example of exploitation.

这回答了您的直接问题（了解出了什么问题）。

现在，您应该对其进行调试，然后缩小问题范围。特问下一个问题，不再编辑

从头开始编写 heapify 函数，得到 "stack-based buffer overrun"

Writing heapify function from scratch, getting a "stack-based buffer overrun"

c++

heap

buffer-overrun