Segmentation fault while mallocing 2d arrays?

Question

I am getting a segmentation fault on line 57 and am not sure why...:

41    int numRows = C/(K*L);
42    int numCols = K;
43  
44    tagArray = (int **) malloc(numRows*sizeof(int)); // creates rows in array with C/K*L rows
45    lruArray = (int **) malloc(numRows*sizeof(int)); // creates rows in array with C/K*L rows
46  
47    for(int i = 0; i<numRows;i++)
48      {
49        *(tagArray + i) = (int*) malloc(numCols*sizeof(int)); // fills each row with K columns
50        *(lruArray + i) = (int*) malloc(numCols*sizeof(int)); // fills each row with K columns
51      }
52  
53    for(int i = 0; i<numRows; i++)
54      for(int j = 0; j<numCols; j++)
55        {
56          tagArray[i][j] = -1;
57          lruArray[i][j] = -1;
58        }
59

Is there something that i'm missing? I'm pretty confident that I am mallocing correctly..

Swordfish · Accepted Answer · 2018-10-07 20:26:25Z

1

In

tagArray = (int **) malloc(numRows*sizeof(int)); // creates rows in array with C/K*L rows
lruArray = (int **) malloc(numRows*sizeof(int)); // creates rows in array with C/K*L rows

you have to allocate space for an int* not an int.

Do not cast the result of malloc() in C!

answered Oct 7, 2018 at 20:26

Swordfish

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0___________ · Accepted Answer · 2018-10-07 20:30:36Z

1

44    tagArray = malloc(numRows*sizeof(int *));
45    lruArray = malloc(numRows*sizeof(int *));
46  
47    for(int i = 0; i<numRows;i++)
48      {
49        tagArray[i] = malloc(numCols*sizeof(int));
50        lruArray[i] = malloc(numCols*sizeof(int));
51      }

answered Oct 7, 2018 at 20:30

0___________

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