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SafeERC20Lib

A library providing safe wrappers around ERC20 token operations. It handles tokens that return false on failure, tokens that don’t return a value, and validates that the target address contains code.

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Overview

Many ERC20 tokens have non-standard implementations that either:
  • Don’t return a boolean value from transfer, transferFrom, or approve
  • Return false instead of reverting on failure
  • Have other quirks that break standard assumptions
SafeERC20Lib ensures all these cases are handled correctly by checking return values and validating success.

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Functions

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safeTransfer

function safeTransfer(address token, address to, uint256 value) internal
Safely transfers tokens from the current contract to a recipient.
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token
address
required
The ERC20 token contract address
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to
address
required
The recipient address
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value
uint256
required
The amount of tokens to transfer
Reverts with:
  • NoCode() - If the token address has no contract code
  • TransferReverted() - If the transfer call reverted
  • TransferReturnedFalse() - If the transfer returned false

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safeTransferFrom

function safeTransferFrom(address token, address from, address to, uint256 value) internal
Safely transfers tokens from one address to another using the ERC20 allowance mechanism.
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token
address
required
The ERC20 token contract address
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from
address
required
The address to transfer tokens from (must have given approval)
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to
address
required
The recipient address
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value
uint256
required
The amount of tokens to transfer
Reverts with:
  • NoCode() - If the token address has no contract code
  • TransferFromReverted() - If the transferFrom call reverted
  • TransferFromReturnedFalse() - If the transferFrom returned false

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safeApprove

function safeApprove(address token, address spender, uint256 value) internal
Safely approves a spender to transfer tokens on behalf of the current contract.
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token
address
required
The ERC20 token contract address
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spender
address
required
The address authorized to spend tokens
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value
uint256
required
The allowance amount
Reverts with:
  • NoCode() - If the token address has no contract code
  • ApproveReverted() - If the approve call reverted
  • ApproveReturnedFalse() - If the approve returned false
Some tokens (like USDT) require the allowance to be set to 0 before changing it to a non-zero value. This library does not handle that case automatically. Set the allowance to 0 first if needed.

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Error handling

All functions in this library:
  1. Check for contract code - Ensures the token address has code before attempting a call
  2. Check call success - Verifies the low-level call didn’t revert
  3. Check return value - If a value is returned, verifies it decodes to true
This three-layer check ensures compatibility with:
  • Standard ERC20 tokens that return true on success
  • Tokens that don’t return any value (empty return data)
  • Tokens that return false on failure instead of reverting

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Usage example

import {SafeERC20Lib} from "./libraries/SafeERC20Lib.sol";

contract MyVault {
    using SafeERC20Lib for address;

    function deposit(address token, uint256 amount) external {
        // Safe transfer from user to vault
        token.safeTransferFrom(msg.sender, address(this), amount);
    }

    function withdraw(address token, uint256 amount) external {
        // Safe transfer from vault to user
        token.safeTransfer(msg.sender, amount);
    }

    function approveSpender(address token, address spender, uint256 amount) external {
        // Safe approval
        token.safeApprove(spender, amount);
    }
}
See ErrorsLib for the error definitions:
  • NoCode()
  • TransferReverted()
  • TransferReturnedFalse()
  • TransferFromReverted()
  • TransferFromReturnedFalse()
  • ApproveReverted()
  • ApproveReturnedFalse()