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Update EIP-6780: Add clarifications to EIP-6780 #7308

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Update EIP-6780: Add clarifications to EIP-6780 #7308

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Add clarifications to EIP-6780
shemnon Jul 11, 2023
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SELFDESTRUCT always halts.
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Merge branch 'master' into 6780-clarifications
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39 changes: 26 additions & 13 deletions EIPS/eip-6780.md
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Expand Up @@ -27,37 +27,50 @@ The behaviour of `SELFDESTRUCT` is changed in the following way:

1. When `SELFDESTRUCT` is executed in a transaction that is not the same as the contract calling `SELFDESTRUCT` was created:

- `SELFDESTRUCT` does not delete any storage keys or code
- `SELFDESTRUCT` transfers the entire account balance to the target.
- No refund is given, as per [EIP-3529](./eip-3529.md).
- [EIP-2929](./eip-2929.md)'s rules regarding `SELFDESTRUCT` remain unchanged.
- The current execution frame halts.
- `SELFDESTRUCT` does not delete any data (including storage keys, code, or the account itself).
- `SELFDESTRUCT` transfers the entire account balance to the target.
- Note that if the target is the same as the contract calling `SELFDESTRUCT` there is no net change in balances. Unlike the prior specification, Ether will not be burnt in this case.
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- Note that no refund is given since [EIP-3529](./eip-3529.md).
- Note that the rules of [EIP-2929](./eip-2929.md) regarding `SELFDESTRUCT` remain unchanged.

2. When `SELFDESTRUCT` is executed in the same transaction as the contract was created:
2. When `SELFDESTRUCT` is executed in the same transaction as the contract was created:

- `SELFDESTRUCT` continues to behave as originally, i.e. deletes all storage keys and the account itself.
- Subsequently, the account will behave like exactly like an empty account, both in the same transaction and in all later ones
- Transfer the account balance to the target **and** set account balance to `0.`
- Note that no refund is given since [EIP-3529](./eip-3529.md).
- Note that the rules of [EIP-2929](./eip-2929.md) regarding `SELFDESTRUCT` remain unchanged.
- Note that when verkle tries are implemented on Ethereum, the cleared storage will be marked as having been written before but empty. This leads to no observable differences in EVM execution, but a contract having been created and deleted will lead to different state roots compared to the action not happening.
- `SELFDESTRUCT` continues to behave as it did prior to this EIP, this includes the following actions
- The current execution frame halts.
- `SELFDESTRUCT` deletes data as previously specified.
- `SELFDESTRUCT` transfers the entire account balance to the target
- The account balance of the contact calling `SELFDESTRUCT` is set to `0`.
- Note that if the target is the same as the contract calling `SELFDESTRUCT` that Ether will be burnt.
- Note that no refund is given since [EIP-3529](./eip-3529.md).
- Note that the rules of [EIP-2929](./eip-2929.md) regarding `SELFDESTRUCT` remain unchanged.
- Note that when verkle tries are implemented on Ethereum, the cleared storage will be marked as having been written before but empty. This leads to no observable differences in EVM execution, but a contract having been created and deleted will lead to different state roots compared to the action not happening.

A contract is considered created at the beginning of a create transaction or when a CREATE series operation begins execution (CREATE, CREATE2, and other operations that deploy contracts in the future). If a balance exists at the contract's new address it is still considered to be a contract creation.

The `SELFDESTRUCT` opcode remains deprecated as specified in [EIP-6049](./eip-6049.md). Any use in newly deployed contracts is strongly discouraged even if this new behaviour is taken into account, and future changes to the EVM might further reduce the functionality of the opcode.

## Rationale

Getting rid of the `SELFDESTRUCT` opcode has been considered in the past, and there are currently no strong reasons to use it. This EIP implements a behavior that will attempt to leave some common uses of `SELFDESTRUCT` working, while reducing the complexity of the change on EVM implementations that would come from contract versioning. A further option that was considered was to just remove storage clearing from `SELFDESTRUCT` in [EIP-6046](./eip-6046.md) while preserving removal of contracts, however this is not safe because existing contracts rely on storage being empty when they are deployed.

Handling the account creation and contract creation as two distinct and possibly separate events is needed for use cases such as counterfactual accounts. By allowing the `SELFDESTRUCT` to delete the account at contract creation time it will not result in stubs of counterfactually instantiated contracts that never had any on-chain state other than a balance prior to the contract creation. These accounts would never have any storage and thus the trie updates to delete the account would be limited to the account node, which is the same impact a regular transfer of ether would have.

## Backwards Compatibility

This EIP requires a hard fork, since it modifies consensus rules.

The only breaking change occurs when a contract is re-created at the same address using `CREATE2` (after a `SELFDESTRUCT`), where the `SELFDESTRUCT` is executed in a transaction that's different from the one that originally creates the contract.
Contracts that depended on re-deploying contracts at the same address using `CREATE2` (after a `SELFDESTRUCT`) will no longer function properly if the created contract does not call `SELFDESTRUCT` within the same transaction.

Previously it was possible to burn ether by calling `SELFDESTRUCT` targeting the executing contract as the beneficiary. If the contract existed prior to the transaction the ether will not be burned. If the contract was newly created in the transaction the ether will be burned, as before.
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## Security Considerations

The following applications of `SELFDESTRUCT` will be broken and applications that use it in this way are not safe anymore:

2. Where `CREATE2` is used to redeploy a contract in the same place in order to make a contract upgradable. This is not supported anymore and [ERC-2535](./eip-2535.md) or other types of proxy contracts should be used instead.
1. Where `CREATE2` is used to redeploy a contract in the same place in order to make a contract upgradable. This is not supported anymore and [ERC-2535](./eip-2535.md) or other types of proxy contracts should be used instead.

2. Where a contract depended on burning Ether via a `SELFDESTRUCT` with the contract as beneficiary, in a contract not created within the same transaction.

## Copyright

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