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    • โœ”๏ธGas Saving Technique 1: Unchecked Arithmetic
    • โ›“๏ธGas Saving Technique 2: Immutable Variable
    • โœจGas Saving Technique 3: Double star ** inefficiency
    • ๐Ÿ’ฐGas Saving Technique 4: Cache Array Length
    • โฌ…๏ธGas Saving Technique 5: ++i costs less gas compared to i++
    • โš–๏ธGas Saving Technique 6: NOT operator ! cheaper than boolean FALSE
    • ๐ŸชกGas Saving Technique 7: Using Short Reason Strings
    • ๐ŸชตGas Saving Technique 8: Use Custom Errors instead of Revert Strings to save Gas
    • โœ’๏ธGas Saving Technique 9: Use Custom Errors instead of Revert Strings to save Gas
    • ๐Ÿ‘พGas Saving Technique 10: Calldata cheaper than memory
    • โ›”Gas Saving Technique 11: > 0 is less efficient than != 0 for unsigned integers
    • โž—Gas Saving Technique 12: SafeMath no longer needed
    • ๐Ÿ˜ฎGas Saving Technique 13: variables default to 0
    • ๐ŸงฑGas Saving Technique 14: struct layout/ variable packing
    • ๐Ÿ“žGas Saving Technique 15: Cache External Call
    • โœ๏ธGas Saving Technique 16: Early Validation before external call
    • ๐Ÿ˜ŽGas Saving Technique 17: Donโ€™t cache value that is used once
    • ๐Ÿ˜งGas Saving Technique 18: Redundant code
    • โœ…Gas Saving Technique 19: Early Validation before external call
    • โ›๏ธGas Saving Technique 20: Storage vs Memory read optimizations
    • โœ’๏ธGas Saving Technique 21: Unneeded If statements
    • ๐ŸŒ—Gas Saving Technique 22: >= is cheaper than >
    • ๐ŸŽ’Gas Saving Technique 23: Public to private constants
    • โน๏ธGas Saving Technique 24: Make unchanged variables constant/immutable
    • โฑ๏ธGas Saving Techniques 25: Redundant Access Control Checks
    • โžก๏ธGas Saving Technique 26: Shift Right instead of Dividing by 2
    • ๐ŸชƒGas Saving Tutorial 27: Efficient Boolean Comparison
    • ๐ŸคGas Saving Technique 28: && operator uses more gas
    • ๐Ÿ‘“Gas Saving Technique 29: x = x + y is cheaper than x += y
    • ๐Ÿ‘‚Gas Saving Technique 30: Using 1 and 2 rather than 0 and 1 saves gas
    • โšฝGas Saving Technique 31: Optimize Storage by Avoiding Booleans
    • ๐Ÿ”™Gas Saving Technique 32: Optimal Use of Named Return Variables in Solidity
    • ๐Ÿ›ข๏ธGas Saving Technique 33: Making Functions Payable for Optimized Gas Costs
    • โœ๏ธGas Saving Technique 34: Optimizing Storage References in Smart Contracts
    • โ›ฐ๏ธGas Saving Technique 35: Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
    • ๐ŸŒช๏ธGas Saving Technique 36: Inlining Single Use Internal Functions for Savings
    • โ˜„๏ธGas Saving Technique 37: Switching from Public to External Functions for Savings
    • ๐ŸŽ†Gas Saving Technique 38: Upgrading Solidity Compiler to Improve Gas Efficiency and Security
    • ๐Ÿ•ถ๏ธGas Saving Technique 39: Avoiding Duplicated Code for Gas Savings
    • ๐Ÿ˜„Gas Saving Technique 40: Removal of Unused Internal Functions for Gas Savings
    • ๐Ÿ–‹๏ธGas Saving Tutorial 41: In-lining Single Use Modifiers For Gas Saving
    • โ›๏ธGas Saving Technique 42: `require` vs`assert`
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Gas Saving Technique 8: Use Custom Errors instead of Revert Strings to save Gas

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Last updated 1 year ago

Introduction

Smart contract optimization often involves subtle adjustments that cumulatively result in significant gas savings. An impactful enhancement introduced in Solidity v0.8.4 is the utilization of custom errors. Custom errors provide a more gas-efficient alternative to revert strings for conveying failure reasons in your smart contracts, thereby reducing both deployment and runtime costs.

Impact & Details

Understanding Gas Consumption

  • Expense of Revert Strings: Traditional revert strings are costly in terms of gas, both during the deployment phase and at runtime when a revert condition is triggered. This expense arises because strings are relatively heavy, and each character consumes gas.

  • Efficiency of Custom Errors: Custom errors, introduced in Solidity v0.8.4, provide a more gas-efficient way to handle error messaging. These errors are not only cheaper to deploy but also consume less gas when invoked, making them a superior choice for error handling.

How to Implement Custom Errors for Gas Savings

Practical Example: Using Custom Errors

Consider a contract where you need to ensure that the sent value is above a certain threshold. Below, you can find the contract versions before and after optimization:

Before Optimization:

solidityCopy code// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Fundraiser {
    uint constant minContribution = 100;

    function contribute() public payable {
        require(msg.value >= minContribution, "Contribution too small");
    }
}

After Optimization:

solidityCopy code// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

contract Fundraiser {
    uint constant minContribution = 100;
    
    error SmallContribution(uint256 valueSent, uint256 minValue);

    function contribute() public payable {
        if (msg.value < minContribution) {
            revert SmallContribution(msg.value, minContribution);
        }
    }
}

In the optimized version, a custom error SmallContribution is defined and used for reverting when the contribution is too small. This approach not only provides clear error messaging but also saves gas compared to the traditional revert string method.

Recommended Mitigation Steps

  1. Identify Revert Strings: Review your smart contracts for require or revert statements with string messages.

  2. Implement Custom Errors: Replace identified revert strings with custom errors, taking advantage of this feature in Solidity v0.8.4 and above.

  3. Test: Perform rigorous testing to verify that the updated smart contract maintains its functionality while using less gas for error handling.

Conclusion

The introduction of custom errors in Solidity offers developers a more gas-efficient mechanism for error handling. While the gas saved per transaction might be modest, the aggregate savings across multiple transactions can be substantial. Always ensure to conduct comprehensive testing after implementing these changes, confirming that the smart contract behaves as expected with the added benefit of reduced gas consumption.

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