C/C++：「試圖讀取或寫入保護內存」異常

Question

我的代碼編譯，但會引發以下異常：

An unhandled exception of type 'System, Access Violation Exception' occured Additional Information: Attempted to read or write protected memory. . .

的錯誤與s=s+a[z][r]*b[f][h]

這裏的副本代碼：

#include"stdafx.h" 
#include"iostream" 
using namespace std; 
int main() 
{ 
    int **a, **b; 
    int z, r, f, h, a_r, a_c, b_r, b_c, s = 0; 

    cout << "Enter the size of the matrix(nxm) :" << endl; 
    cin >> a_r >> a_c; 

    cout << "enter the size of the mask :" << endl; 
    cin >> b_r >> b_c; 

    a = (int **) malloc(10 * a_r); 
    for (int i = 0; i < a_c; i++) 
    { 
     a[i] = (int *) malloc(10 * a_c); 
    } 

    b = (int **) malloc(10 * b_r); 
    for (int i = 0; i < b_c; i++) 
    { 
     b[i] = (int *) malloc(10 * b_c); 
    } 

    for (int i = 0; i < a_r; i++) 
    { 
     for (int j = 0; j < a_c; j++) 
     { 
      a[i][j] = i + j; 
     } 
    } 

    for (int i = 0; i < b_r; i++) 
    { 
     for (int j = 0; j < b_c; j++) 
     { 
      b[i][j] = i + j; 
     } 
    } 

    int k = 1, d = 1; 
    for (int i = 0; i < a_r; i++) 
    { 
     for (int j = 0; j < a_c; j++) 
     { 
      for (int n = -1; n <= 1; n++) 
      { 
       for (int e = -1; e <= 1; e++) 
       { 
        z = i + n; 
        r = j + e; 
        f = k + n; 
        h = d + e; 
        if (z < 0 || z > a_r || r < 0 || r > a_c) 
        { 
         s = s + 0; 
        } else { 
         s = s + a[z][r] * b[f][h]; // runtime error occurs here 
        } 
       } 
      } 
      a[i][j] = s; 
      s = 0; 
     } 
    } 
    return 0; 
} 

Answer 1

這裏有一個問題：

   if (z < 0 || z > a_r || r < 0 || r > a_c) 

這應該閱讀：

   if (z < 0 || z >= a_r || r < 0 || r >= a_c) 

否則，你可能訪問外的邊界元素。