Since v0.8.0, Solidity supports overflow and underflow checks for arithmetic operations, but inline assembly does not. This discrepancy necessitates a custom implementation to ensure the same level of safety when working with assembly code. This library presents a SafeMath library written in inline assembly to provide these essential checks, preventing potential vulnerabilities in smart contracts that rely on low-level arithmetic operations.
The SafeMath library includes four arithmetic functions (add, sub, mul, div) with overflow and underflow checks using assembly. Custom errors enhance readability and debugging.
One of the complex operation was the division, let’s Breakdown of Division Function:
- Division by Zero Check: Ensures rhs is not zero.
- INT256_MIN/-1 Check: Prevents overflow when lhs is INT256_MIN and rhs is -1.
eq(lhs, 0x8000...0000): Checks if the left-hand side is equal to INT256_MIN (the smallest possible int256).eq(rhs, 0xffff...ffff): Checks if the right-hand side is equal to -1 in two's complement representation.
This part prevents the overflow that would occur when dividing INT256_MIN by -1, as the result (2^255) is too large to be represented in an int256.
- Division Operation: Performs signed division using
sdiv.
If you are developing smart contracts and using assembly/Yul code, this SafeMath library will definitely assist you, especially with complex arithmetic operations. By ensuring overflow and underflow checks, it offers a reliable way to handle arithmetic in low-level assembly, crucial for maintaining contract integrity and security.
While this project demonstrates high code quality and rigorous testing, it has not been audited and should be used cautiously.