Delete empty account at BEACON_ROOTS_ADDRESS

[gurukamath]

What was wrong?

The current implementation of EIP-4788 did not delete the account at BEACON_ROOTS_ADDRESS if it is empty after being touched by the system message call. For example, in a case where the contract has not been deployed yet. EIP-4788 does not explicitly mention this deletion but it is implied post EIP-161

How was it fixed?

Delete the account at BEACON_ROOTS_ADDRESS if it is empty.

[codecov-commenter]

Codecov Report

Attention: 2112 lines in your changes are missing coverage. Please review.

Comparison is base (bf47143) 69.96% compared to head (4938522) 69.83%.
Report is 25 commits behind head on forks/cancun.

Files	Patch %	Lines
src/ethereum/cancun/fork.py	0.00%	236 Missing ⚠️
src/ethereum/cancun/vm/instructions/system.py	0.00%	207 Missing ⚠️
src/ethereum/cancun/vm/instructions/__init__.py	0.00%	162 Missing ⚠️
src/ethereum/cancun/vm/instructions/environment.py	0.00%	153 Missing ⚠️
src/ethereum/cancun/state.py	0.00%	149 Missing ⚠️
src/ethereum/cancun/vm/interpreter.py	0.00%	112 Missing ⚠️
src/ethereum/cancun/vm/instructions/arithmetic.py	0.00%	109 Missing ⚠️
src/ethereum/cancun/vm/instructions/stack.py	0.00%	98 Missing ⚠️
src/ethereum/cancun/vm/gas.py	0.00%	97 Missing ⚠️
src/ethereum/cancun/vm/__init__.py	0.00%	77 Missing ⚠️
... and 35 more

Additional details and impacted files

@@               Coverage Diff                @@
##           forks/cancun     #871      +/-   ##
================================================
- Coverage         69.96%   69.83%   -0.13%     
================================================
  Files               610      610              
  Lines             34295    34773     +478     
================================================
+ Hits              23993    24283     +290     
- Misses            10302    10490     +188     

Flag	Coverage Δ
unittests	69.83% <12.69%> (-0.13%)	⬇️

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[SamWilsn]

Hm, is it necessary to check again after running destroy_touched_empty_accounts?

[gurukamath]

Oh. This is an error. Will update.

[petertdavies]

The question of whether BEACON_ROOTS_ADDRESS gets cleared is verifiably moot, because the account is not empty and cannot become empty. My recollection is that it was decided to remove the test from execution-spec-tests, rather than force everyone to implement this. If that's the case I don't see why we should be added code to the specs.

[gurukamath]

The question of whether BEACON_ROOTS_ADDRESS gets cleared is verifiably moot, because the account is not empty and cannot become empty. My recollection is that it was decided to remove the test from execution-spec-tests, rather than force everyone to implement this. If that's the case I don't see why we should be added code to the specs.

The way the ethereum/tests for cancun are currently filled, this account can end up being touched and empty. Will check with the team. @marioevz Any comments on this?

[marioevz]

Execution spec tests fix: ethereum/execution-spec-tests#425

Still looking into ethereum/tests.

[chfast]

This is by design unspecified because this cannot happen in practice.

[gurukamath]

Opened issue for this to be fixed in the ethereum/tests repo

[chfast]

EIP-7523 fixes this because then the BEACON_ROOTS_ADDRESS cannot be empty in the pre-state.

[winsvega]

but can it be non existent?
and if it is non existent then if no code exists at BEACON_ROOTS_ADDRESS, the call must fail silently
meanin the current ethereum/tests are correct

[chfast]

Exactly. Most of the tests don't have the BEACON_ROOTS_ADDRESS code in the state and they work fine. The system call works as a call to a non-existent account.

[winsvega]

but then there is this option which is also legal - to just write storages without a silent call. it creates double reading.
because writing storages directly is not a call so it does not fail.

I think it would be better if:

if there is no contract in the state. deploy contract to the state. make silent call / write storages
if contrac alsready in the state verify it has nonce = 1, code = CODE