test_create_child_halt_refunds_state_gas()

Documentation for tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_create.py::test_create_child_halt_refunds_state_gas@c74f1a67.

Generate fixtures for these test cases for Amsterdam with:

fill -v tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_create.py::test_create_child_halt_refunds_state_gas --fork Amsterdam

Verify CREATE/CREATE2 child halt refunds parent's account gas.

Exceptional halts (invalid opcode, EIP-3541 invalid prefix) consume all forwarded gas as regular_gas_used, so block accounting cannot strictly discriminate via header gas. Tight gas tuning via a caller wrapper leaves the factory with just enough gas_left to pay the probe SSTORE's regular portion but not enough to spill the state portion, so the probe SSTORE can only succeed via the refunded reservoir.

Source code in tests/amsterdam/eip8037_state_creation_gas_cost_increase/test_state_gas_create.py

@pytest.mark.parametrize(
    "failure_mode",
    [
        pytest.param("initcode_halt", id="initcode_halt"),
        pytest.param("invalid_prefix", id="invalid_prefix"),
    ],
)
@pytest.mark.with_all_create_opcodes()
@pytest.mark.valid_from("EIP8037")
def test_create_child_halt_refunds_state_gas(
    state_test: StateTestFiller,
    pre: Alloc,
    fork: Fork,
    create_opcode: Op,
    failure_mode: str,
) -> None:
    """
    Verify CREATE/CREATE2 child halt refunds parent's account gas.

    Exceptional halts (invalid opcode, EIP-3541 invalid prefix)
    consume all forwarded gas as `regular_gas_used`, so block
    accounting cannot strictly discriminate via header gas. Tight
    gas tuning via a caller wrapper leaves the factory with just
    enough `gas_left` to pay the probe SSTORE's regular portion
    but not enough to spill the state portion, so the probe SSTORE
    can only succeed via the refunded reservoir.
    """
    gas_costs = fork.gas_costs()
    sstore_state_gas = Op.SSTORE(new_value=1).state_cost(fork)
    new_account_state_gas = gas_costs.NEW_ACCOUNT

    init_code: Op | Bytecode
    if failure_mode == "initcode_halt":
        init_code = Op.INVALID
    elif failure_mode == "invalid_prefix":
        # Return code starting with 0xEF (EIP-3541 invalid prefix).
        init_code = Op.MSTORE8(0, 0xEF) + Op.RETURN(0, 1)

    mstore_value, size = init_code_at_high_bytes(init_code)

    create_call = (
        create_opcode(value=0, offset=0, size=size, salt=0)
        if create_opcode == Op.CREATE2
        else create_opcode(value=0, offset=0, size=size)
    )

    storage = Storage()
    factory = pre.deploy_contract(
        code=(
            Op.MSTORE(0, mstore_value)
            + Op.POP(create_call)
            + Op.SSTORE(storage.store_next(1, "reservoir_ok"), 1)
        ),
    )

    # Tight gas tuning: child halt consumes all forwarded gas as
    # regular_gas_used. Factory retains
    # ~(forwarded - pre_sstore_regular) / 64 after CREATE. Target
    # the discrimination window `(probe_regular,
    # probe_regular + sstore_state_gas)` so the probe SSTORE
    # regular fits but state gas spillover from `gas_left` under
    # the old behavior OOGs.
    pre_sstore_code = Op.MSTORE(0, mstore_value) + Op.POP(create_call)
    pre_sstore_regular = pre_sstore_code.gas_cost(fork) - new_account_state_gas
    probe_code = Op.SSTORE(0, 1)
    probe_regular = probe_code.gas_cost(fork) - sstore_state_gas
    target_gas_left = probe_regular + sstore_state_gas // 2
    forwarded_gas = target_gas_left * 64 + pre_sstore_regular
    # Reservoir sized for CREATE charge only — SSTORE must pull
    # from the refunded reservoir, not from spill.
    caller = pre.deploy_contract(
        code=Op.CALL(gas=forwarded_gas, address=factory)
    )
    tx = Transaction(
        to=caller,
        state_gas_reservoir=new_account_state_gas,
        sender=pre.fund_eoa(),
    )

    state_test(pre=pre, post={factory: Account(storage=storage)}, tx=tx)

Parametrized Test Cases

This test generates 4 parametrized test cases across 1 fork.