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ECLIP-?: Byzantium EVM upgrades (and Tx Receipt status) #2

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ECLIP-?: Byzantium EVM upgrades (and Tx Receipt status) #2

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### ECLIP-?: Support for ETH Byzantium EVM and Protocol Upgrades

ECLIP: undecided
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Please make this ECIP-1054 as per #9 (#5)

Suggested change
ECLIP: undecided
ECIP: 1054

Title: Support for ETH Byzantium EVM and Protocol Upgrades
Status: Draft
Type: Standards Track
Author: Isaac Ardis <isaac.a@etclabs.org>
Created: 2019-02-11

### Abstract

Add support for a subset of protocol-impacting changes introduced in the Ethereum Foundation (ETH) network via the _Byzantium_ hardfork. The proposed changes include:

- Byzantium EVM opcodes and precompiled contracts, namely opcodes `REVERT` (EIP 206/140), `RETURNDATASIZE` (EIP 211), `RETURNDATACOPY` (EIP 211), and `STATICCALL` (EIP 214/116); and precompiled contracts for modular exponentiation, elliptic curve addition, scalar multiplication, and pairing (EIPs 198, 212/197, 213/196)
- Replacing the intermediate state root field in transaction receipts with the contract return status (EIP 658).

This document proposes block `X,XXX,XXX` as the upcoming block height at which to implement these changes in the network, placing the expected date of protocol hardfork date on _XXXX-XX-XX_.
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@soc1c soc1c Mar 18, 2019 •
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This needs some thought. The release process should allow for a hard-fork on the testnets (Morden, Kotti) at least 4 weeks prior to the mainnet activation. Assuming Byzantium is well tested on Ethereum Foundation network, we can just rephrase this like

Suggested change
This document proposes block `X,XXX,XXX` as the upcoming block height at which to implement these changes in the network, placing the expected date of protocol hardfork date on _XXXX-XX-XX_.
This document proposes blocks:
- `X_XXX_XXX` on Ethereum Classic mainnet
- `X_XXX_XXX` on Morden Classic testnet
- `X_XXX_XXX` on Kotti Classic testnet

Edit: date should not be part of the proposal as it is a moving target naturally.

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That said,

  • Ethereum Classic block 8_750_000 will be around Wed, Sept 18, 2019
  • Morden Classic block 4_723_000 will be around Wed, Aug 7, 2019
  • Kotti Classic block 1_039_000 will be around Wed, Aug 7, 2019

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@soc1c can you make this as a suggestion? (cmd+g in the comment box)

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Done.

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Edit: date should not be part of the proposal as it is a moving target naturally.

Proposing:

Suggested change
This document proposes block `X,XXX,XXX` as the upcoming block height at which to implement these changes in the network, placing the expected date of protocol hardfork date on _XXXX-XX-XX_.

or?

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No. I said date.


For more information on the opcodes and their respective EIPs and implementations, please see the __History__ section of this document.

### Motivation

To enhance the EVM's capabilities by adding 5 opcodes and 4 precompiled contracts, all of which have been in use on the ETH network since 2017-10-16. Adoption of the "receipt status" feature provides a helpful method for Dapp developers to access the successful or failed state of a contract. This would (re)establish a greater level of interoperability between Foundation and Classic Ethereum Virtual Machines ("EVM"s), and make a wider array of tooling available for the ETC network (eg. Solidity version, several contract debugging tools).
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It's only 4 opcodes right? Also, the first one is not a sentence.

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ref #10


This protocol specification notably omits the scheduled features of the anticipated _Constantinople_ fork, which would be expected to include various further EVM upgrades. The reasoning for this omission hinges on a hedge toward battle-testing of those changes in light of multiple delays of that fork ([here](https://medium.com/ethereum-cat-herders/a-post-mortem-report-the-constantinople-ethereum-hard-fork-postponement-dd780d7ae63d), a postmortem of the latest delay) due to security and implementation discrepencies.

### Specification

As per associated EIPs's specifications and implementations, with feature-readiness determined by interoperability (implementation) of smart contracts utilizing the introduced opcode and precompiled contracts (implementation before technical specification in case of discrepency). Technical specifications for each EIP can be found at those documents respectively.

### Rationale

__Interoperability__: establishing and maintaining interoperable behavior between Ethereum clients is important for developers and end-user adoption, yielding benefits for all participating chains (eg. ETH and ETC).

__On Immutability__: Introducing new opcodes in the VM has the potential to change behavior of existing contracts; in the case where previously an arbitrary invalid bytecode series (yielding _invalid opcode_) would now be assigned a meaning, and thus could generate or return a value other than _invalid_. In essence, this means "possibly making music where there was only noise before." There is a concern that this behavior change contradicts an essential promise of Immutability, since an existing failing smart contract is liable to become a succeeding (not failing) contract, albeit in a hypothetical case of extreme coincidence and gross misuse of an opcode. In counterargument to this concern are two critical points:

1. account states remain unchanged
2. the "Homestead" hardfork established a precedent for this type of change, having introduced the `DELEGATECALL` opcode at block 1,150,000.
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@BelfordZ BelfordZ Feb 18, 2019 •
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Suggested change
2. the "Homestead" hardfork established a precedent for this type of change, having introduced the `DELEGATECALL` opcode at block 1,150,000.
2. if a person used one of the unimplemented opcodes originally, the behaviour was undefined. In this right - the immutability property remains since the behaviour will be equally undefined once the op code is implemented.

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what if we make another ECLIP and propose that transactions using invalid / unused opcodes are to be deemed invalid transactions and never included in blocks.

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fwiw...i think there is an unavoidable risk that upgrades with hard forks may break some past smart contracts. If this is the case I think that "no hard forks" or "no innovation" isn't a solution either. If there is a "best practices" way for smart contract devs to keep them within a safe boundary that is their responsibility, similar to the responsibility of exchanges of using more confirmations to minimize double spend risks.

Having said that, the goal of ETC devs should still be to minimize such risk in changes and prioritize "backward compatibility" over change just for the sake of change.

Because this is largely subjective, I guess the ECIP (or new starIP) process, and then deployment by node operators and miners, is a good filter to judge that.


With these arguments in place, along with precedence and expectation for other continuing and varied consensus-impacting protocol upgrades (eg soft- and hard-forks), it follows that the definition of Immutability is not extended to guarantee perfect consistency for future _behavior_ of historical account states, but only to only to guarantee the immutability of the account states themselves.
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From a semantic prospective adding an opcode would be classified as a "non-breaking-change". A feature upgrade. Might be worth pointing out. You do a good job of highlighting the cons to your own ECLIP but I think they all have good pro counter arguments.

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That's false. Adding an opcode would always be a "breaking change", no matter if you consider old contracts that already contain this opcode, or consider hard fork as a whole.

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It's a hard fork yes. But considering old contracts. This would be a feature upgrade not a major version change (i.e 0.1.0 not 1.0.0). Any new feature of software will always technically change behavior. But it's only when you look at extreme, un-supported, ways of using it.

Thats even true with the versioning proposal. Adding a 00 byte in front of a contract had a behavior before, it will have a different behavior now

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Using semantic versioning to consider something as fragile as consensus upgrade is totally unhealthy. Ethereum community's experience tells us that we must consider all upgrades as breaking, regardless how small or how big you think it is. On top of that, we consider what invariant we want to preserve, and what doesn't matter. Otherwise it can easily bring in disaster. You need to especially look out for "extreme, un-supported, ways of using it" and consider them to make sure everything's okay.

Thats even true with the versioning proposal. Adding a 00 byte in front of a contract had a behavior before, it will have a different behavior now

Sure, but do I miss some points you try to claim? Account versioning would of course be a breaking change.

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@sorpaas I'm all for being careful 👍. Im just saying that adding useful opcodes likely does not break any intended contract behavior. But I agree that as with any major changes, we should tread lightly and test well.


Adding opcodes and precompiled contracts to the EVM increases its functionality (only in an extremely rare case of gross misuse would be seen to _change_ it's functionality), and should be considered a feature upgrade rather than a modification.

### Implementation

Adoption of the content of this ECLIP requires a hard fork, and herein that adoption is proposed to be scheduled for block X,XXX,XXX roughly estimated to arrive _XXXX-XX-XX_.

The `ethereumproject/go-ethereum` client implemented an API-only (non-consensus impacting) partial adoption of EIP-658 receipt status code change via the [v5.5.0](https://github.com/ethereumproject/go-ethereum/releases/tag/v5.5.0) release, and this proposal would augment that change to extend through to the RLP encoding (and thus modify consensus protocol).

ETC Labs Core advocates and supports the adoption of [ethoxy/multi-geth](https://github.com/ethoxy/multi-geth) as a fully-featured and maintenance-scheduled client for this fork and beyond.

### History

##### Byzantium changes

These changes were introduced in the `ethereum/go-ethereum` client via the [1.7 "Megara" release](https://github.com/ethereum/go-ethereum/releases/tag/v1.7.0).

These changes are catalogued via the EIP process in the following:

- EIP-658: Transaction receipts embedding status code instead of intermediate state root field - https://github.com/ethereum/EIPs/pull/658/files

- EIP-140: `REVERT` - https://github.com/ethereum/EIPs/pull/206/files

> The `REVERT` instruction provides a way to stop execution and revert state changes, without consuming all provided gas and with the ability to return a reason.


- EIP-211: `RETURNDATASIZE`, `RETURNDATACOPY` - https://github.com/ethereum/EIPs/pull/211/files

> A mechanism to allow returning arbitrary-length data inside the EVM has been requested for quite a while now. Existing proposals always had very intricate problems associated with charging gas. This proposal solves the same problem while at the same time, it has a very simple gas charging mechanism and requires minimal changes to the call opcodes. Its workings are very similar to the way calldata is handled already; after a call, return data is kept inside a virtual buffer from which the caller can copy it (or parts thereof) into memory. At the next call, the buffer is overwritten. This mechanism is 100% backwards compatible.


- EIP-214: `STATICCALL` - https://github.com/ethereum/EIPs/pull/214/files

> To increase smart contract security, this proposal adds a new opcode that can be used to call another contract (or itself) while disallowing any modifications to the state during the call (and its subcalls, if present).

- EIP-198: Precompiled contract for modular exponentiation - https://github.com/ethereum/EIPs/pull/198/files

- EIP-212: Precompiled contract for elliptic curve pairing - https://github.com/ethereum/EIPs/pull/212/files

- EIP-213: Precompiled contracts for elliptic curve addition and scalar multiplication - https://github.com/ethereum/EIPs/pull/213/files