I am writing a Crowdsale contract but function buyTokens does not run and throws an error ,
execution reverted: SafeERC20: low-level call failed { “originalError”: { “code”: 3, “data”: “0x08c379a0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000205361666545524332303a206c6f772d6c6576656c2063616c6c206661696c6564”, “message”: “execution reverted: SafeERC20: low-level call failed” } }
Environment
Details
Error seems to be from SafeERC20 library. Deployment of token & crowdsale contracts is smooth.
My code is given below:
Code to reproduce
// SPDX-License-Identifier: MIT
pragma solidity ^0.5.0;
interface IERC20 {
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function transfer(address recipient, uint256 amount) external returns (bool);
function allowance(address owner, address spender) external view returns (uint256);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);
}
library SafeMath {
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
require(c >= a, "SafeMath: addition overflow");
return c;
}
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
return sub(a, b, "SafeMath: subtraction overflow");
}
function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b <= a, errorMessage);
uint256 c = a - b;
return c;
}
function mul(uint256 a, uint256 b) internal pure returns (uint256) {
if (a == 0) {
return 0;
}
uint256 c = a * b;
require(c / a == b, "SafeMath: multiplication overflow");
return c;
}
function div(uint256 a, uint256 b) internal pure returns (uint256) {
return div(a, b, "SafeMath: division by zero");
}
function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
// Solidity only automatically asserts when dividing by 0
require(b > 0, errorMessage);
uint256 c = a / b;
// assert(a == b * c + a % b); // There is no case in which this doesn't hold
return c;
}
function mod(uint256 a, uint256 b) internal pure returns (uint256) {
return mod(a, b, "SafeMath: modulo by zero");
}
function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
require(b != 0, errorMessage);
return a % b;
}
}
library Roles {
struct Role {
mapping (address => bool) bearer;
}
function add(Role storage role, address account) internal {
require(!has(role, account), "Roles: account already has role");
role.bearer[account] = true;
}
function remove(Role storage role, address account) internal {
require(has(role, account), "Roles: account does not have role");
role.bearer[account] = false;
}
function has(Role storage role, address account) internal view returns (bool) {
require(account != address(0), "Roles: account is the zero address");
return role.bearer[account];
}
}
library SafeERC20 {
using SafeMath for uint256;
using Address for address;
function safeTransfer(IERC20 token, address to, uint256 value) internal {
callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
}
function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
}
function safeApprove(IERC20 token, address spender, uint256 value) internal {
require((value == 0) || (token.allowance(address(this), spender) == 0),
"SafeERC20: approve from non-zero to non-zero allowance"
);
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
}
function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).add(value);
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
}
function callOptionalReturn(IERC20 token, bytes memory data) private {
require(address(token).isContract(), "SafeERC20: call to non-contract");
(bool success, bytes memory returndata) = address(token).call(data);
require(success, "SafeERC20: low-level call failed");
if (returndata.length > 0) { // Return data is optional
// solhint-disable-next-line max-line-length
require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
}
}
}
contract ReentrancyGuard {
bool private _notEntered;
constructor () internal {
_notEntered = true;
}
modifier nonReentrant() {
// On the first call to nonReentrant, _notEntered will be true
require(_notEntered, "ReentrancyGuard: reentrant call");
// Any calls to nonReentrant after this point will fail
_notEntered = false;
_;
// By storing the original value once again, a refund is triggered (see
// https://eips.ethereum.org/EIPS/eip-2200)
_notEntered = true;
}
}
library Address {
function isContract(address account) internal view returns (bool) {
bytes32 codehash;
bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
// solhint-disable-next-line no-inline-assembly
assembly { codehash := extcodehash(account) }
return (codehash != accountHash && codehash != 0x0);
}
function toPayable(address account) internal pure returns (address payable) {
return address(uint160(account));
}
function sendValue(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");
// solhint-disable-next-line avoid-call-value
(bool success, ) = recipient.call.value(amount) ("");
require(success, "Address: unable to send value, recipient may have reverted");
}
}
contract Context {
function _msgSender() internal view returns (address payable) {
return msg.sender;
}
function _msgData() internal view returns (bytes memory) {
this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
return msg.data;
}
}
contract ERC20 is Context, IERC20 {
using SafeMath for uint256;
mapping (address => uint256) private _balances;
mapping (address => mapping (address => uint256)) private _allowances;
uint256 private _totalSupply;
function totalSupply() public view returns (uint256) {
return _totalSupply;
}
function balanceOf(address account) public view returns (uint256) {
return _balances[account];
}
function transfer(address recipient, uint256 amount) public returns (bool) {
_transfer(_msgSender(), recipient, amount);
return true;
}
function allowance(address owner, address spender) public view returns (uint256) {
return _allowances[owner][spender];
}
function approve(address spender, uint256 amount) public returns (bool) {
_approve(_msgSender(), spender, amount);
return true;
}
function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
_transfer(sender, recipient, amount);
_approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(amount, "ERC20: transfer amount exceeds allowance"));
return true;
}
function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
return true;
}
function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
_approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
return true;
}
function _transfer(address sender, address recipient, uint256 amount) internal {
require(sender != address(0), "ERC20: transfer from the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
_balances[sender] = _balances[sender].sub(amount, "ERC20: transfer amount exceeds balance");
_balances[recipient] = _balances[recipient].add(amount);
emit Transfer(sender, recipient, amount);
}
function _mint(address account, uint256 amount) internal {
require(account != address(0), "ERC20: mint to the zero address");
_totalSupply = _totalSupply.add(amount);
_balances[account] = _balances[account].add(amount);
emit Transfer(address(0), account, amount);
}
function _burn(address account, uint256 amount) internal {
require(account != address(0), "ERC20: burn from the zero address");
_balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
_totalSupply = _totalSupply.sub(amount);
emit Transfer(account, address(0), amount);
}
function _approve(address owner, address spender, uint256 amount) internal {
require(owner != address(0), "ERC20: approve from the zero address");
require(spender != address(0), "ERC20: approve to the zero address");
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
}
function _burnFrom(address account, uint256 amount) internal {
_burn(account, amount);
_approve(account, _msgSender(), _allowances[account][_msgSender()].sub(amount, "ERC20: burn amount exceeds allowance"));
}
}
contract ERC20Detailed is IERC20 {
string private _name;
string private _symbol;
uint8 private _decimals;
constructor (string memory name, string memory symbol, uint8 decimals) public {
_name = name;
_symbol = symbol;
_decimals = decimals;
}
function name() public view returns (string memory) {
return _name;
}
function symbol() public view returns (string memory) {
return _symbol;
}
function decimals() public view returns (uint8) {
return _decimals;
}
}
contract AnnaToken is Context, ERC20, ERC20Detailed {
constructor(
string memory name,
string memory symbol,
uint256 initialSupply
) public ERC20Detailed(name, symbol, 0) {
_mint(_msgSender(), initialSupply);
}
}
contract Crowdsale is Context, ReentrancyGuard {
using SafeMath for uint256;
using SafeERC20 for IERC20;
// The token being sold
IERC20 private _token;
// Address where funds are collected
address payable private _wallet;
// How many token units a buyer gets per wei.
// The rate is the conversion between wei and the smallest and indivisible token unit.
// So, if you are using a rate of 1 with a ERC20Detailed token with 3 decimals called TOK
// 1 wei will give you 1 unit, or 0.001 TOK.
uint256 private _rate;
uint256 private _price;
// Amount of wei raised
uint256 private _weiRaised;
/**
* Event for token purchase logging
* @param purchaser who paid for the tokens
* @param beneficiary who got the tokens
* @param value weis paid for purchase
* @param amount amount of tokens purchased
*/
event TokensPurchased(address indexed purchaser, address indexed beneficiary, uint256 value, uint256 amount);
/**
* rate Number of token units a buyer gets per wei
* @param price Number of wei a buyer needs to get per token
* @dev The rate is the conversion between wei and the smallest and indivisible
* token unit. So, if you are using a rate of 1 with a ERC20Detailed token
* with 3 decimals called TOK, 1 wei will give you 1 unit, or 0.001 TOK.
* @param wallet Address where collected funds will be forwarded to
* @param token Address of the token being sold
*/
constructor (uint256 price, address payable wallet, IERC20 token) public {
require(price > 0, "Crowdsale: rate is 0");
require(wallet != address(0), "Crowdsale: wallet is the zero address");
require(address(token) != address(0), "Crowdsale: token is the zero address");
_price = price;
_wallet = wallet;
_token = token;
}
/**
* @dev fallback function ***DO NOT OVERRIDE***
* Note that other contracts will transfer funds with a base gas stipend
* of 2300, which is not enough to call buyTokens. Consider calling
* buyTokens directly when purchasing tokens from a contract.
*/
function () external payable {
buyTokens(_msgSender());
}
/**
* @return the token being sold.
*/
function token() public view returns (IERC20) {
return _token;
}
/**
* @return the address where funds are collected.
*/
function wallet() public view returns (address payable) {
return _wallet;
}
/**
* @return the number of token units a buyer gets per wei.
*/
function rate() public view returns (uint256) {
return _rate;
}
function price() public view returns (uint256) {
return _price;
}
/**
* @return the amount of wei raised.
*/
function weiRaised() public view returns (uint256) {
return _weiRaised;
}
/**
* @dev low level token purchase ***DO NOT OVERRIDE***
* This function has a non-reentrancy guard, so it shouldn't be called by
* another `nonReentrant` function.
* @param beneficiary Recipient of the token purchase
*/
function buyTokens(address beneficiary) public nonReentrant payable {
uint256 weiAmount = msg.value;
_preValidatePurchase(beneficiary, weiAmount);
// calculate token amount to be created
uint256 tokens = _getTokenAmount(weiAmount);
// update state
_weiRaised = _weiRaised.add(weiAmount);
_processPurchase(beneficiary, tokens);
emit TokensPurchased(_msgSender(), beneficiary, weiAmount, tokens);
_updatePurchasingState(beneficiary, weiAmount);
_forwardFunds();
_postValidatePurchase(beneficiary, weiAmount);
}
/**
* @dev Validation of an incoming purchase. Use require statements to revert state when conditions are not met.
* Use `super` in contracts that inherit from Crowdsale to extend their validations.
* Example from CappedCrowdsale.sol's _preValidatePurchase method:
* super._preValidatePurchase(beneficiary, weiAmount);
* require(weiRaised().add(weiAmount) <= cap);
* @param beneficiary Address performing the token purchase
* @param weiAmount Value in wei involved in the purchase
*/
function _preValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
require(beneficiary != address(0), "Crowdsale: beneficiary is the zero address");
require(weiAmount != 0, "Crowdsale: weiAmount is 0");
this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
}
/**
* @dev Validation of an executed purchase. Observe state and use revert statements to undo rollback when valid
* conditions are not met.
* @param beneficiary Address performing the token purchase
* @param weiAmount Value in wei involved in the purchase
*/
function _postValidatePurchase(address beneficiary, uint256 weiAmount) internal view {
// solhint-disable-previous-line no-empty-blocks
}
/**
* @dev Source of tokens. Override this method to modify the way in which the crowdsale ultimately gets and sends
* its tokens.
* @param beneficiary Address performing the token purchase
* @param tokenAmount Number of tokens to be emitted
*/
function _deliverTokens(address beneficiary, uint256 tokenAmount) internal {
_token.safeTransfer(beneficiary, tokenAmount);
}
/**
* @dev Executed when a purchase has been validated and is ready to be executed. Doesn't necessarily emit/send
* tokens.
* @param beneficiary Address receiving the tokens
* @param tokenAmount Number of tokens to be purchased
*/
function _processPurchase(address beneficiary, uint256 tokenAmount) internal {
_deliverTokens(beneficiary, tokenAmount);
}
/**
* @dev Override for extensions that require an internal state to check for validity (current user contributions,
* etc.)
* @param beneficiary Address receiving the tokens
* @param weiAmount Value in wei involved in the purchase
*/
function _updatePurchasingState(address beneficiary, uint256 weiAmount) internal {
// solhint-disable-previous-line no-empty-blocks
}
/**
* @dev Override to extend the way in which ether is converted to tokens.
* @param weiAmount Value in wei to be converted into tokens
* @return Number of tokens that can be purchased with the specified _weiAmount
*/
function _getTokenAmount(uint256 weiAmount) internal view returns (uint256) {
return weiAmount.div(_price);
}
/**
* @dev Determines how ETH is stored/forwarded on purchases.
*/
function _forwardFunds() internal {
_wallet.transfer(msg.value);
}
}
contract AnnaCrowdsale is Crowdsale {
constructor(
uint256 rate,
address payable wallet,
IERC20 token
) public Crowdsale(rate, wallet, token) {}
}