FV-SOL-6-C3 Silent Fail

TLDR

A function call fails without detection, and continues executing as if it succeeded, which can create an invalid or inconsistent state.

Game

Silent fails are scary and can be unpredictable. can you find what can cause a silent fail here?

Code

// SPDX-License-Identifier: MIT
// Open me in VSCode and really think before opening the hints!
// Add @audit tags wherever suspicious
// Go to the solidity docs to complete missing knowledge of what's happening here
// Solve by drafting a fix!
pragma solidity ^0.8.0;

interface IExternalContract {
    function performAction() external returns (bool);
}

contract SilentFailGame {
    IExternalContract public externalContract;

    constructor(address _externalContract) {
        externalContract = IExternalContract(_externalContract);
    }

    function callExternalAction() public {
        externalContract.performAction();
    }
}

Hint 1

Consider the return type of performAction and whether ignoring it might cause issues. How can you confirm that the function actually succeeded?

Hint 2

Adding a check on the return value can help ensure that you handle failures explicitly rather than assuming success.

Solution

function callExternalAction() public {
    bool success = externalContract.performAction();
    require(success, "External action failed"); // Fix: Check return value to catch failure
}