Thread: Unhandled exception

Here is the relevant code:

Code:

string getVal(vector<vector<string>> * matrix, int row, int col)
{
  row--;//account for offsets
  col--;
  try
  {
    if(row >= 0 && col >= 0 && col < cols && row < rows)//make sure it is inbound
      return (*matrix)[row][col];
    else
      throw "Out of Bounds Error!";
  }
  catch (const char * ex)
  {
    cout << "\n*** " << ex << " ***" << endl;
  }
}

The boundaries
cols is 4
rows is 4

and row is 5, col is 3
It catches the error and prints out *** Out of Bounds Error!***
but then a window pops up saying

Unhandled exception at 0x62907a8b ...
Access violation reading location 0xc0e8013e

I am running this in MS visual studio 2008

I suggest that you #include <stdexcept> and write it in this way:

Code:

string getVal(const vector<vector<string>>& matrix, int row, int col)
{
    // account for offsets
    --row;
    --col;

    // make sure it is within bound
    if (row < 0 || col < 0 || col >= cols || row >= rows)
    {
        throw out_of_range("Out of Bounds Error!");
    }

    return matrix[row][col];
}

Now, to call it would be something like this:

Code:

try
{
    string str = getVal(matrix, row, col);
    // ...
}
catch (const out_of_range& ex)
{
    cout << "\n*** " << ex.what() << " ***" << endl;
}

Originally Posted by Mirage

I've added a return NULL; right after the print statement but this opens up a new problem

That is not really correct. You might return an empty string, but not NULL, which is zero. The point of my example is that I don't have to cater for this, because if the arguments are out of range, the exception is throw, rather than thrown and then caught at the same place, leading to a path of control where nothing is returned despite the return type not being void.

Originally Posted by Mirage

just wondering but you changed the pointer parameter to a reference for readability issues, right?

Yes, and also because a null pointer is not a valid argument anyway.