Solidity – Troubleshooting High Gas Usage by Fallback Functions

contract-developmentgassolidity

This is my contract and logic inside fallback function is not so complicated, but why does it tell that my fallback function requires too much gas? How do I fix this problem?

pragma solidity ^0.4.16;

contract owned {
    address public owner;

    function owned() public {
        owner = msg.sender;
    }

    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }

    function transferOwnership(address newOwner) onlyOwner public {
        owner = newOwner;
    }
}

interface tokenRecipient { function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) public; }

contract MyCoin {
    // Public variables of the token
    string public name = "MyCoin";
    string public symbol = "XYZ";
    uint8 public decimals = 18;
    // 18 decimals is the strongly suggested default, avoid changing it
    uint256 public totalSupply;
    uint256 initialSupply = 50000000;

    // This creates an array with all balances
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;

    // This generates a public event on the blockchain that will notify clients
    event Transfer(address indexed from, address indexed to, uint256 value);

    // This notifies clients about the amount burnt
    event Burn(address indexed from, uint256 value);

    /**
     * Constrctor function
     *
     * Initializes contract with initial supply tokens to the creator of the contract
     */
    function MyCoin() public {
        totalSupply = initialSupply * 10 ** uint256(decimals);  // Update total supply with the decimal amount
        balanceOf[msg.sender] = totalSupply;                // Give the creator all initial tokens
        //name = tokenName;                                   // Set the name for display purposes
        //symbol = tokenSymbol;                               // Set the symbol for display purposes
    }

    /**
     * Internal transfer, only can be called by this contract
     */
    function _transfer(address _from, address _to, uint _value) internal {
        // Prevent transfer to 0x0 address. Use burn() instead
        require(_to != 0x0);
        // Check if the sender has enough
        require(balanceOf[_from] >= _value);
        // Check for overflows
        require(balanceOf[_to] + _value > balanceOf[_to]);
        // Save this for an assertion in the future
        uint previousBalances = balanceOf[_from] + balanceOf[_to];
        // Subtract from the sender
        balanceOf[_from] -= _value;
        // Add the same to the recipient
        balanceOf[_to] += _value;
        Transfer(_from, _to, _value);
        // Asserts are used to use static analysis to find bugs in your code. They should never fail
        assert(balanceOf[_from] + balanceOf[_to] == previousBalances);
    }

    /**
     * Transfer tokens
     *
     * Send `_value` tokens to `_to` from your account
     *
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transfer(address _to, uint256 _value) public {
        _transfer(msg.sender, _to, _value);
    }

    /**
     * Transfer tokens from other address
     *
     * Send `_value` tokens to `_to` in behalf of `_from`
     *
     * @param _from The address of the sender
     * @param _to The address of the recipient
     * @param _value the amount to send
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_value <= allowance[_from][msg.sender]);     // Check allowance
        allowance[_from][msg.sender] -= _value;
        _transfer(_from, _to, _value);
        return true;
    }

    /**
     * Set allowance for other address
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     */
    function approve(address _spender, uint256 _value) public
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        return true;
    }

    /**
     * Set allowance for other address and notify
     *
     * Allows `_spender` to spend no more than `_value` tokens in your behalf, and then ping the contract about it
     *
     * @param _spender The address authorized to spend
     * @param _value the max amount they can spend
     * @param _extraData some extra information to send to the approved contract
     */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        public
        returns (bool success) {
        tokenRecipient spender = tokenRecipient(_spender);
        if (approve(_spender, _value)) {
            spender.receiveApproval(msg.sender, _value, this, _extraData);
            return true;
        }
    }

    /**
     * Destroy tokens
     *
     * Remove `_value` tokens from the system irreversibly
     *
     * @param _value the amount of money to burn
     */
    function burn(uint256 _value) public returns (bool success) {
        require(balanceOf[msg.sender] >= _value);   // Check if the sender has enough
        balanceOf[msg.sender] -= _value;            // Subtract from the sender
        totalSupply -= _value;                      // Updates totalSupply
        Burn(msg.sender, _value);
        return true;
    }

    /**
     * Destroy tokens from other account
     *
     * Remove `_value` tokens from the system irreversibly on behalf of `_from`.
     *
     * @param _from the address of the sender
     * @param _value the amount of money to burn
     */
    function burnFrom(address _from, uint256 _value) public returns (bool success) {
        require(balanceOf[_from] >= _value);                // Check if the targeted balance is enough
        require(_value <= allowance[_from][msg.sender]);    // Check allowance
        balanceOf[_from] -= _value;                         // Subtract from the targeted balance
        allowance[_from][msg.sender] -= _value;             // Subtract from the sender's allowance
        totalSupply -= _value;                              // Update totalSupply
        Burn(_from, _value);
        return true;
    }
}

/******************************************/
/*       ADVANCED TOKEN STARTS HERE       */
/******************************************/

contract MyAdvancedToken is owned, MyCoin {

    uint256 public sellPrice = 500;
    uint256 public buyPrice = 500;
    uint256 private endTime = 123456; //@TODO

    mapping (address => bool) public frozenAccount;

    /* This generates a public event on the blockchain that will notify clients */
    event FrozenFunds(address target, bool frozen);

    /* Initializes contract with initial supply tokens to the creator of the contract */
    function MyAdvancedToken() MyCoin() public {}

    /* Internal transfer, only can be called by this contract */
    function _transfer(address _from, address _to, uint _value) internal {
        require (_to != 0x0);                               // Prevent transfer to 0x0 address. Use burn() instead
        require (balanceOf[_from] > _value);                // Check if the sender has enough
        require (balanceOf[_to] + _value > balanceOf[_to]); // Check for overflows
        require(!frozenAccount[_from]);                     // Check if sender is frozen
        require(!frozenAccount[_to]);                       // Check if recipient is frozen
        balanceOf[_from] -= _value;                         // Subtract from the sender
        balanceOf[_to] += _value;                           // Add the same to the recipient
        Transfer(_from, _to, _value);
    }

    /// @notice Create `mintedAmount` tokens and send it to `target`
    /// @param target Address to receive the tokens
    /// @param mintedAmount the amount of tokens it will receive
    function mintToken(address target, uint256 mintedAmount) onlyOwner public {
        balanceOf[target] += mintedAmount;
        totalSupply += mintedAmount;
        Transfer(0, this, mintedAmount);
        Transfer(this, target, mintedAmount);
    }

    /// @notice `freeze? Prevent | Allow` `target` from sending & receiving tokens
    /// @param target Address to be frozen
    /// @param freeze either to freeze it or not
    function freezeAccount(address target, bool freeze) onlyOwner public {
        frozenAccount[target] = freeze;
        FrozenFunds(target, freeze);
    }

    /// @notice Allow users to buy tokens for `newBuyPrice` eth and sell tokens for `newSellPrice` eth
    /// @param newSellPrice Price the users can sell to the contract
    /// @param newBuyPrice Price users can buy from the contract
    function setPrices(uint256 newSellPrice, uint256 newBuyPrice) onlyOwner public {
        sellPrice = newSellPrice;
        buyPrice = newBuyPrice;
    }

    /// @notice Buy tokens from contract by sending ether
    function () payable public {

        //this is minimum what you can buy
        require(msg.value >= 1 / buyPrice);

        //ICO has to be active
        require(now < endTime);

        //get amount of tokens to send to the seller
        uint amount = calculateAmount(msg.value);
        uint bonus = getBonus(amount);

        //Xmas or NewYear give them 50% more tokens
        //uint bonus = ;

        _transfer(this, msg.sender,  amount + bonus);
    }

    /**
     * Get bonus for Xmas and New Year
     */
    function getBonus(uint _amount) constant private returns (uint256) {
        if(now >= 5000 && now <= 5001 || now >= 6000 && now <= 6001) { //@TODO pripremi vrijeme, dodaj jos koji random dan za popuste
            return _amount * 50 / 100;
        }  

        return 0;
    }

    /**
     * Calculate how mush XYZ you need to send
     */
    function calculateAmount(uint _amount) constant private returns (uint256) {
        //phase 1 (10 days)
        if(now >= 1000 && now <= 20000) { //@TODO
            // calculates the amount
            return _amount * buyPrice + (buyPrice * 50 / 100);
        } 
        //phase 2 (15 days)
        else if (now >= 1000 && now <= 20000) { //@TODO
            return _amount * buyPrice;
        } 
        //phase 3 (20 days)
        else {
            return _amount * buyPrice - (buyPrice * 50 / 100);
        }
    }

    /// @notice Sell `amount` tokens to contract
    /// @param amount amount of tokens to be sold
    function sell(uint256 amount) public {
        require(this.balance >= amount * sellPrice);      // checks if the contract has enough ether to buy
        _transfer(msg.sender, this, amount);              // makes the transfers
        msg.sender.transfer(amount * sellPrice);          // sends ether to the seller. It's important to do this last to avoid recursion attacks
    }
}

Best Answer

Your fallback function performs token transfer, and token transfer modifies token holder balances in contract's storage. Any storage modification costs more than 2300 gas, and fallback function, when called with no data, is supposed to fit into 2300 gas. If fallback function does not fit into 2300 gas when called with no data, then ether cannot be sent to your contract from other contracts via send or transfer functions. Though, ether may still be sent to your contract from plain (non-contract) Ethereum accounts, and ether may still be sent to your contract from other contracts via call or selfdestruct functions. Many crowdsale contracts have fallback functions that do not fit into 2300 gas.

P.S. Most multisig wallets use call function to send ether, so it will be possible to send ether from multisig wallets to your contract even if fallback function in your contract does not fit into 2300 gas.

Related Solutions

[Ethereum] Token transfer: Intrinsic gas too low

I suspect that your issue is because you have not approved the transfer required to call transferFrom(...).

Here are the relevant functions:

    /* Send coins */
    function transfer(address _to, uint256 _value) {
        if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
        balanceOf[msg.sender] -= _value;                     // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
        Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
    }

    /* Allow another contract to spend some tokens in your behalf */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        tokenRecipient spender = tokenRecipient(_spender);
        spender.receiveApproval(msg.sender, _value, this, _extraData);
        return true;
    }

    /* A contract attempts to get the coins */
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw;  // Check for overflows
        if (_value > allowance[_from][msg.sender]) throw;   // Check allowance
        balanceOf[_from] -= _value;                          // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
        allowance[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value);
        return true;
    }

If you are the current owner of the tokens, you can call transfer(...) to transfer your balance to another address.

However if you want to transfer from another address, you will need to call transferFrom(...) which will check the allowance[...][...] data structure to confirm whether this transfer has been approved.

So, call approveAndCall(...) first to approve your transfer and you should be able to call transferFrom(...) to transfer your tokens.

When you call transferFrom(...) without first calling approveAndCall(...), and error is thrown in the line

if (_value > allowance[_from][msg.sender]) throw;   // Check allowance

This error will appear as an Out Of Gas error in the Ethereum Wallet.

If you are comfortable using geth, see How can the transaction status from a thrown error be detected when gas can be exactly the same as the gasUsed for a successful transaction? for the following code that can be used to check the exact reason for your error:

> var status = debug.traceTransaction("0xd23219e2ea10528b245deb9e47993cae2ffd3ffe9fc27aeb808e94fc4e75d37b")
undefined
> if (status.structLogs.length > 0) {
  console.log(status.structLogs[status.structLogs.length-1].error)
}
"invalid jump destination (PUSH1) 2"

[Ethereum] API to “Read Contract Information” to fetch stats of an ICO

Which version of web3 are you using?

Here is a working example with web3@^1.0.0-beta.34

const Web3 = require('web3');
contractAddress = '0xe7775a6e9bcf904eb39da2b68c5efb4f9360e08c';
provider = 'https://mainnet.infura.io';
const contractAbiJSON = '';//... The JSON abi

// Init
const web3 = new Web3(new web3.providers.HttpProvider(provider));

const contract = new web3.eth.Contract(contractAbiJSON, contractAddress);

contract.methods.totalSupply().call().then((totalSupply) => {
  console.log(totalSupply);
});

Best Answer

Related Solutions

[Ethereum] Token transfer: Intrinsic gas too low

[Ethereum] API to “Read Contract Information” to fetch stats of an ICO

Related Topic