evm: Read the account also for a 0-byte EXTCODECOPY

[chfast]

EXTCODECOPY skipped Host::copy_code() when copying 0 bytes, unlike
execution-specs which reads the account regardless of the size. Call it
always. For a 0-byte copy pass a null buffer, as for empty LOG data,
because the memory offset may then be out of bounds; the hosts accept
it.

[codspeed]

Merging this PR will degrade performance by 16.67%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 1 regressed benchmark
✅ 898 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	test_extcodecopy_warm[fork_Osaka-blockchain_test-copy_size_0-benchmark-gas-value_1M]	7.2 ms	8.6 ms	-16.67%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing evm/extcodecopy-zero-size (a89c91f) with master (39425f3)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.07%. Comparing base (39425f3) to head (a89c91f).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1753   +/-   ##
=======================================
  Coverage   98.06%   98.07%           
=======================================
  Files         183      183           
  Lines       16940    16944    +4     
  Branches     3873     3876    +3     
=======================================
+ Hits        16613    16617    +4     
  Misses        245      245           
  Partials       82       82           

Flag	Coverage Δ
eest-develop-gmp	25.86% <61.53%> (-0.01%)	⬇️
eest-legacy	17.05% <53.84%> (+<0.01%)	⬆️
eest-libsecp256k1	28.05% <61.53%> (-0.01%)	⬇️
eest-stable	83.88% <100.00%> (+<0.01%)	⬆️
evmone-unittests	94.24% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
core	96.25% <100.00%> (+<0.01%)	⬆️
tooling	94.29% <ø> (ø)
tests	99.81% <100.00%> (+<0.01%)	⬆️

Files with missing lines	Coverage Δ
lib/evmone/instructions.hpp	99.53% <100.00%> (+<0.01%)	⬆️
test/unittests/evm_eip2929_test.cpp	100.00% <100.00%> (ø)

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[Copilot]

🟢 Approval recommended

The implementation matches the specified behavior and safely avoids dereferencing invalid memory for zero-length copies.

0 open findings

What changed in this PR

Ensures zero-byte EXTCODECOPY still reads the target account while safely handling out-of-bounds memory offsets.

Changes:

• Always invokes Host::copy_code(), using a null buffer for zero-byte copies.
• Updates EIP-2929 account-access expectations.

File	Description
lib/​evmone/​instructions.hpp	Corrects zero-byte EXTCODECOPY behavior.
test/​unittests/​evm_eip2929_test.cpp	Verifies the additional account reads.

🧠 Review effort: Balanced

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