[英]Visual studio - buffer overrun
Having this code:有这个代码:
#include <iostream>
#include <math.h>
#include <algorithm>
double abs_length(int * ar)
{
return (
sqrt(pow(double(ar[0]), 2) + pow(double(ar[1]), 2))
);
}
int ** correction(int size, int(*ar)[2], int refX, int refY)
{
int **ar2 = new int*[2];
for (int i = 0; i < size; i++)
{
int x = abs(ar[i][0] - refX);
int y = abs(ar[i][1] - refY);
int vector[2] = { x,y };
ar2[i] = vector;
}
return ar2;
}
double median(int size, int(*ar)[2], int refX, int refY)
{
int **coordinates = correction(size, ar, refX, refY);
double* lengths = new double(size);
for (int i = 0; i < size; i++)
{
lengths[i] = abs_length(coordinates[i]);
}
sort(lengths, lengths + size);
return size % 2 == 0 ? (lengths[(size / 2) - 1] + lengths[size]) / 2 :
lengths[(size / 2) - 1];
}
And for而对于
lengths[i] = abs_length(coordinates[i]);
I am getting warning (which ends up with fatal error):我收到警告(最终出现致命错误):
Buffer overrun while writing to 'lengths': the writable size is '1*8' bytes, but '16' bytes might be writen.
I do not understand it.我不明白。 Why could be 16 bytes written, when
double
is sizeof 8?当
double
的 sizeof 8 时,为什么可以写入 16 个字节? 16 is address, but abs_length
is returning double, no pointer. 16 是地址,但
abs_length
返回双abs_length
值,没有指针。 So where is bug?那么bug在哪里呢?
There's an error here这里有一个错误
int ** correction(int size, int(*ar)[2], int refX, int refY)
{
int **ar2 = new int*[2];
for (int i = 0; i < size; i++)
{
int x = abs(ar[i][0] - refX);
int y = abs(ar[i][1] - refY);
int vector[2] = { x,y };
ar2[i] = vector;
}
return ar2;
}
The lines线条
int vector[2] = { x,y };
ar2[i] = vector;
create a local array and stores a pointer to that array.创建一个本地数组并存储一个指向该数组的指针。 The array is destroyed when you exit the body of the for loop, so you are storing a pointer to an object which has been destroyed.
当您退出 for 循环体时,数组将被销毁,因此您正在存储一个指向已被销毁的对象的指针。
This code would work这段代码会起作用
int* vector = new int[2];
vector[0] = x;
vector[1] = y;
ar2[i] = vector;
There may be other errors, far too many pointers in your code.可能还有其他错误,代码中的指针太多。
You made a typo:你打错了:
new double(size)
allocates space for a single double with value size
.为值为
size
的单个双精度分配空间。
You probably meant:你可能的意思是:
new double[size]
which allocates space for an array of size
doubles.它为
size
翻倍的数组分配空间。
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