/**
* @dev This abstract contract provides getters and event emitting update functions for
* https://eips.ethereum.org/EIPS/eip-1967[EIP1967] slots.
*
* _Available since v4.1._
*
* @custom:oz-upgrades-unsafe-allow delegatecall
*/
abstract contract ERC1967Upgrade {
// This is the keccak-256 hash of "eip1967.proxy.rollback" subtracted by 1
bytes32 private constant _ROLLBACK_SLOT = 0x4910fdfa16fed3260ed0e7147f7cc6da11a60208b5b9406d12a635614ffd9143;
/**
* @dev Storage slot with the address of the current implementation.
* This is the keccak-256 hash of "eip1967.proxy.implementation" subtracted by 1, and is
* validated in the constructor.
*/
bytes32 internal constant _IMPLEMENTATION_SLOT = 0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc;
/**
I don't understand the need for the -1 to get the slot for the implementation. Tested it out in solidity and it always returns the same value.
Skyge
December 26, 2022, 8:01am
2
Hi, welcome to the community!
I think just in order to reduce the chances of a possible attack, cause we do not know the original data to calculate hash for this slot. And for more details, I think you can have a look at EIP-1967: Proxy Storage Slots
