Which library was previously used to prevent arithmetic overflows in Solidity?

SafeMath was widely used in Solidity to prevent arithmetic overflows and underflows, particularly in versions of Solidity before the introduction of built-in overflow checks in Solidity 0.8.0. SafeMath provides a set of arithmetic operations such as addition, subtraction, multiplication, and division with added safety checks that revert transactions if an overflow or underflow occurs.

By wrapping these operations in functions that include both the arithmetic operation and the overflow checks, SafeMath ensures that developers can handle mathematical calculations without the risk of unintentionally producing incorrect results due to exceeding data type limits. This library became a common standard across many smart contracts to enhance security and reliability.

With the advancement of Solidity, particularly from version 0.8.0 onward, these overflow checks are inherently built into the language's arithmetic operations, making the use of SafeMath less critical. However, its prominence in earlier versions underscores the importance of managing arithmetic operations securely in smart contracts.