抛出异常:读取访问冲突.**dynamicArray** 是 0x1118235.发生了 [英] Exception thrown: read access violation. **dynamicArray** was 0x1118235. occurred

问题描述

#include "pch.h"
#include <iostream>
#include <string>
using namespace std;
int **dynamicArray ;
int ROWS, COLUMNS;

//---------------------------------
int input_matrix(int ROWS, int COLUMNS)
{

    //---------------------------------------
    //memory allocated for elements of rows.
    int **dynamicArray = new int *[ROWS];

    //memory allocated for  elements of each column.
    for (int i = 0; i < ROWS; i++)
        dynamicArray[i] = new int [COLUMNS];

    //free the allocated memory
    for (int i = 0; i < ROWS; i++)
        delete[] dynamicArray[i];
    delete[] dynamicArray;
    //-------------------------------------

    for (int i = 0; i < ROWS; i++)
    {
        for (int j = 0; j < COLUMNS; j++)
        {
            cin >> dynamicArray[i][j];
        }
    }
    return 0;
}
//---------------------------------------------
int print_matrix(int **Array)
{
    for (int k = 0; k < ROWS; k++)
    {
        for (int m = 0; m < COLUMNS; m++)
        {
            cout << Array[k][m];
            if (m == COLUMNS)
            {
                cout << "
";
            }
        }
    }

    return 0;

}

//---------------------------------
int main()
{
    cin >> ROWS;
    cin >> COLUMNS;
    input_matrix(ROWS, COLUMNS);
    print_matrix(dynamicArray);

}

此代码定义了一个矩阵并获取输入并将它们放入矩阵的成员中，但每次运行此代码时，我都会在线上出现读取访问冲突错误:

This code defines a matrix and get inputs and puts them in the members of the matrix but Every time I run this code I get read access violation error on the line:

cin >> dynamicArray[i][j];

这里是完整的细节:抛出异常:读取访问冲突.dynamicArray 是 0x1118235.发生

here are the full details: Exception thrown: read access violation. dynamicArray was 0x1118235. occurred

我该怎么办?

提前致谢.

推荐答案

您的程序存在多个问题.让我一一列出来.

There are multiple issues with your program. Let me list all of them one by one.

1. 如其中一条评论所述，您立即在分配内存后立即释放内存.绝对是这个将导致分段错误或内存访问冲突，当您访问已释放的内存.
2. 当你分配内存时，你不是将分配的内存指针分配给全局指针dynamicArray 相反，您正在使用函数input_matrix 中的同名.作为这个指针变量范围在您丢失内存的函数内结束分配.因此，您将再次面临分段错误或内存print_matrix 函数内的访问冲突.
3. 在内部 for 循环中的 print_matrix 函数中，您正在检查是否 m==COLUMNS 打印新行，这永远不会发生，因为 m 总是小于 列.
4. 最后，正如前面的答案所暗示的，当您使用 C++ 时，为了更好的内存管理，使用带有智能指针的向量比使用数组和原始指针更好.

1. As mentioned in one of the comments, You are immediately deallocating memory just after you allocated it. Definitely this will result in a segmentation fault or memory access violation when you access deallocated memory.
2. When you allocate the memory you are not assigning the allocated memory pointers to global pointer dynamicArray instead you are creating a local variable with the same name inside the function input_matrix. As this pointer variable scope ends inside the function you are losing the memory allocated. Hence again you will face segmentation fault or memory access violation inside print_matrix function.
3. Inside print_matrix function in inner for loop you are checking if m==COLUMNS to print new line, this will never happen since m is always less than COLUMNS.
4. Finally, as the previous answer suggests when you are using C++, using a vector with smart pointers is a better choice than using array and raw pointers for better memory management.

以下代码段解决了这些问题.

Following snippet resolves those issues.

#include <iostream>
#include <string>
using namespace std;
int **dynamicArray ;
int ROWS, COLUMNS;

//---------------------------------
int input_matrix(int ROWS, int COLUMNS)
{
    //---------------------------------------
    //memory allocated for elements of rows.
    dynamicArray = new int *[ROWS];

    //memory allocated for  elements of each column.
    for (int i = 0; i < ROWS; i++)
        dynamicArray[i] = new int [COLUMNS];

//    cout<<"Input array values
";

    for (int i = 0; i < ROWS; i++)
    {
        for (int j = 0; j < COLUMNS; j++)
        {
            cin>>dynamicArray[i][j];
        }
    }
    return 0;
}

void free_matrix_memory()
{
    cout<<"freeing allocated memory
";
    //free the allocated memory
    for (int i = 0; i < ROWS; i++)
        delete[] dynamicArray[i];
    delete[] dynamicArray;
    //-------------------------------------
}

//---------------------------------------------
int print_matrix(int **Array)
{
    cout<<"printing matrix
";
    for (int k = 0; k < ROWS; k++)
    {
        for (int m = 0; m < COLUMNS; m++)
            cout << Array[k][m];
        cout << "
";
    }
    return 0;
}

//---------------------------------
int main()
{
    cout<<"Row and column values
";
    cin>> ROWS;
    cin>> COLUMNS;
    input_matrix(ROWS, COLUMNS);
    print_matrix(dynamicArray);
    free_matrix_memory();
}

仍然可以为您做许多改进，例如避免全局变量等，我将这些改进留给您.

Still many improvements can be done for your such as avoiding global variables etc., I am leaving it up to you to do those improvements.

这篇关于抛出异常:读取访问冲突.**dynamicArray** 是 0x1118235.发生了的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！