Exercise: Overflow

• Go to https://remix.ethereum.org and select Solidity environment
• Create a new file (+ button in top left), name it

  TestOverflow.sol

• Enter this solidity code:

  pragma solidity ^0.5.0;
  
  contract TestOverflow {
      function addOne(uint256 a) public pure returns(uint256) {
          require(a + 1 > a, "sorry, a is too big");
          return a + 1;
      }
  }
  

• Compile the code with the button in the Compile tab (or typing control-s)
• Deploy the code with the button the the Run tab (it deploys it to a test EVM in your browser by default)
• See your new contract in the Deployed Contracts section of Run tab: "TestOverflow at 0x..."
• Expand the TestOverflow contract
• Enter values in the addOne field and press the addOne label to trigger a transaction to your contract
• Observe the output in the console
• What value do you need to enter to get it to overflow?
• Try using Solidity 0.8+ and observe the change in overflow behaviour