test_extcodecopy_empty_account_composes_additively()

Documentation for tests/amsterdam/eip8038_state_access_gas_cost_increase/test_ext_code_opcodes_gas.py::test_extcodecopy_empty_account_composes_additively@2867859a.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip8038_state_access_gas_cost_increase/test_ext_code_opcodes_gas.py::test_extcodecopy_empty_account_composes_additively --fork Amsterdam

Compose the surcharge additively when copying from an empty account.

EXTCODECOPY of a non-existent source copies zero bytes into memory, yet still charges the account-access cost, the EIP-8038 code-read WARM_ACCESS surcharge, the EIP-150 per-word copy cost (OPCODE_COPY_PER_WORD per word, driven by the requested size, not the source length), and the memory-expansion cost. The measured gas must equal the sum of all four components, confirming the surcharge composes additively even when there is no code to read.

Source code in tests/amsterdam/eip8038_state_access_gas_cost_increase/test_ext_code_opcodes_gas.py

@EIPChecklist.GasCostChanges.Test.GasUpdatesMeasurement()
@pytest.mark.parametrize("warm", [False, True], ids=["cold", "warm"])
@pytest.mark.parametrize(
    "copy_size", [32, 96], ids=["one_word", "three_words"]
)
def test_extcodecopy_empty_account_composes_additively(
    state_test: StateTestFiller,
    env: Environment,
    pre: Alloc,
    fork: Fork,
    warm: bool,
    copy_size: int,
) -> None:
    """
    Compose the surcharge additively when copying from an empty account.

    ``EXTCODECOPY`` of a non-existent source copies zero bytes into memory,
    yet still charges the account-access cost, the EIP-8038 code-read
    ``WARM_ACCESS`` surcharge, the EIP-150 per-word copy cost
    (``OPCODE_COPY_PER_WORD`` per word, driven by the requested size, not
    the source length), and the memory-expansion cost. The measured gas
    must equal the sum of all four components, confirming the surcharge
    composes additively even when there is no code to read.
    """
    # Empty source: never deployed, no code. The copy yields zeros, but the
    # cost is driven by the requested size, identical to a code-bearing
    # source of the same length.
    empty_addr = pre.nonexistent_account()

    oracle = Op.EXTCODECOPY.with_metadata(
        address_warm=warm,
        data_size=copy_size,
        new_memory_size=copy_size,
        old_memory_size=0,
    )
    measured_code = oracle(
        address=empty_addr, dest_offset=0, offset=0, size=copy_size
    )

    expected_gas = oracle.gas_cost(fork)

    code_gas_measure = CodeGasMeasure(
        code=measured_code,
        overhead_cost=measured_code.gas_cost(fork) - oracle.gas_cost(fork),
        extra_stack_items=0,
    )
    measure_address = pre.deploy_contract(code=code_gas_measure)

    tx = Transaction(
        to=measure_address,
        sender=pre.fund_eoa(),
        access_list=[AccessList(address=empty_addr, storage_keys=[])]
        if warm
        else None,
    )

    post = {measure_address: Account(storage={0: expected_gas})}
    state_test(env=env, pre=pre, post=post, tx=tx)

Parametrized Test Cases

This test generates 4 parametrized test cases across 1 fork.