Unity freezes at IndexOutOfRangeException, even though I continue

Question

I have this "Game" class that gets instantiated at Start and sets up the field for Minesweeper and in this process I count the adjacent Mines for each field.

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Game
{
    public int Width;
    public int Height;
    public int NumOfMines;

    public Field[,] Board;
    public Game(int width = 8, int height = 8, int numOfMines = 10)
    {
        this.Width = width;
        this.Height = height;
        this.NumOfMines = numOfMines;
        Board = new Field[height, width];
        InitializeBoard();
    }

    public void InitializeBoard()
    {
        for (int row = 0; row < Height; row++)
        {
            for (int column = 0; column < Width; column++)
            {
                Board[row, column] = new Field();
            }
        }
        
        // Board.Initialize();

        // foreach (var field in Board)
        // {
        //     field.IsMine = false;
        // }
        
        var rnd = new System.Random();
        for (int i = 0; i < NumOfMines; i++)
        {
            int mineRow = 0;
            int mineColumn = 0;
            do
            {
                mineRow = rnd.Next(Height);
                mineColumn = rnd.Next(Width);
            } while (Board[mineRow, mineColumn].IsMine);

            Board[mineRow, mineColumn].IsMine = true;
            Board[mineRow, mineColumn].NumOfAdjacentMines = null;
        }

        for (int row = 0; row < Height; row++)
        {
            for (int column = 0; column < Width; column++)
            {
                if (!Board[column, row].IsMine)
                    Board[row, column].NumOfAdjacentMines = CountAdjacentMines(new Vector2Int(column, row));
            }
        }
    }

    private int CountAdjacentMines(Vector2Int pos)
    {
        Debug.Log(pos);
        int counter = 0;
        for (int y = pos.y - 1; y <= pos.y + 1; y++)
        {
            for (int x = pos.x - 1; y <= pos.x + 1; x++)
            {
                try
                {
                    Debug.Log($"Checking {x + ":" + y} for a mine");
                    if (Board[x, y].IsMine)
                    {
                        counter++;
                    }
                }
                catch (Exception ex)
                {
                    Debug.LogError(ex + ", Pos: " + x + ":" + y);
                    continue;
                }
            }
        }

        return counter;
    }
}

Why does Unity freeze without any notes? If I throw the exception, unity reacts normally. (I have to write this so StackOverflow let's me post this...)

Answer 1

Look at the inner for loop iterating the x variable. Look closely. What is the actual condition that will end/conclude this inner for loop? Look very closely.

Basic answer to your question: Your program freezes, because the inner for loop iterating the x variable is an infinite loop that will never end. It's not Unity that freezes, it's your code getting stuck in this infinite loop. Like a hamster running in his wheel, forever...

(Re)throwing the exception will force this loop to exit, hence no freeze (because, simplified speaking, throwing the exception will abort execution of the CountAdjacentMines method).