ERC20SafeApproveLib

Git Source

Author: Golem Foundation

Library for safe ERC20 approve operations handling non-standard tokens

*Handles tokens that don't return bool or revert silently PROBLEM SOLVED:

• Some tokens (USDT, BNB) don't return bool from approve()
• Some tokens revert silently on approval failure
• Standard Solidity expects bool return value SOLUTION:
• Uses low-level call to handle any return data format
• Validates success flag
• Validates return data if present
• Reverts with ApprovalFailed() on any failure*

Notes:

• security-contact: [email protected]

• security: Critical for compatibility with non-standard ERC20 tokens

Functions

safeApprove

Safely approves ERC20 tokens handling non-standard implementations

*Uses low-level call to handle tokens that:

• Don't return bool (e.g., USDT)
• Return false instead of reverting
• Have non-standard approval behavior*

Note: security: Reverts with ApprovalFailed() on any failure

function safeApprove(address token, address spender, uint256 amount) external;

Parameters

Name	Type	Description
token	address	ERC20 token address
spender	address	Address being approved to spend tokens
amount	uint256	Amount to approve