fix(evm): meter CALLCODE new-account storage gas against caller context

[TroublorBot]

Generated by engineer-agent — review carefully before merging.

Summary

Fixes a bug where CALLCODE was charging new-account storage gas based on the code-source address instead of the caller's storage context. For CALLCODE, execution happens in the caller's account, so the emptiness check must be against the caller, not the code-source. Rex5 gates the fix by using interpreter.input.target_address() for new-account metering, while pre-Rex5 specs preserve frozen behavior for backward compatibility. Includes 4 regression tests covering both the fix and frozen behavior for CALLCODE and CALL.

Fixes #283

[TroublorBot]

🔧 Pushed CI fixes.

Agent log

Labels applied successfully. The `require-label` check needed at least one `spec:`, `comp:`, and `api:` label — all three were missing. I added:

- **`spec:unstable`** — the fix is gated to Rex5, the current unstable spec
- **`comp:core`** + **`comp:doc`** — modifies the core crate and documentation
- **`api:unchanged`** — no public interface changes
- **`rust`** — Rust code changes

The CI check will re-run on the label events and should now pass.

[TroublorBot]

Labels spec:unstable, comp:core, comp:doc, api:unchanged, and rust are all already applied to this PR. No changes needed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.5%. Comparing base (09ceb5d) to head (ddfd4e7).

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[claude]

Review

The fix is semantically correct. CALLCODE executes in the caller's storage context, so target_address() in a CALLCODE frame is the calling contract (confirmed by the existing comment at execution.rs:583). Since the executing contract always has code, state_clear_aware_is_empty is invariably false under Rex5 — which is the right outcome, because CALLCODE's value parameter doesn't actually transfer ETH to the code-source address; it stays within the caller's account context, so no new account is ever created via CALLCODE.

The spec-gating, backward-compatibility freeze, and doc update all look correct.

Minor observation: Under Rex5, inspect_account_delegated(mega_spec, target_address()) loads the executing contract's account only to confirm it's non-empty — which is always true for a contract issuing CALLCODE. The load is harmless but logically redundant. A follow-up micro-optimisation (if it ever matters on this path) would be to skip the lookup for Rex5 and short-circuit to is_empty = false directly. Not a blocker.

Tests cover the four key scenarios (Rex5/Rex4 × CALLCODE/CALL) and correctly pin the frozen pre-Rex5 behaviour. LGTM.

[RealiCZ]

@TroublorBot fix ci

[Troublor]

Refactor suggestion inline: the new call_code is largely a copy of the wrap_call_with_storage_gas! expansion. Consider parameterizing the macro with an optional storage-address selector so CALL/CALLCODE/DELEGATECALL/STATICCALL stay in lockstep on the shared logic. Non-blocking — fix is correct and well-tested.

[Troublor]

The hand-written call_code is ~90% identical to the macro expansion — the only real differences are:

1. The storage address: to (macro) vs. spec-gated target_address()/to (here).
2. Stack[2] inspect being unconditional (CALLCODE always has a value operand).

Everything else — stack inspect for to, inspect_account_delegated, state_clear_aware_is_empty, the is_empty && has_transfer charge, the new_account_storage_gas lookup, the halt/abort branches, and run_inner_instruction_or_abort! — is line-for-line the same. If the shared logic ever changes (e.g. stack-inspect ordering, halt-branch additions), we'd have to remember to update both sites.

Suggestion: parameterize the macro with an optional storage-address selector that defaults to to. Then CALLCODE becomes a normal wrap_call_with_storage_gas! invocation:

macro_rules! wrap_call_with_storage_gas {
    // Default: storage address is the stack `to`.
    ($fn_name:ident, $opcode_name:expr, $wrapped_fn:path, $has_transfer_logic:expr) => {
        wrap_call_with_storage_gas!(
            $fn_name, $opcode_name, $wrapped_fn, $has_transfer_logic, to
        );
    };
    // Custom storage-address selector: `to`, `mega_spec`, `context` are in scope.
    ($fn_name:ident, $opcode_name:expr, $wrapped_fn:path, $has_transfer_logic:expr, $storage_addr:expr) => {
        #[doc = concat!("`", $opcode_name, "` opcode implementation modified from `revm` with compute gas tracking and dynamically-scaled storage gas costs.")]
        pub fn $fn_name<
            WIRE: InterpreterTypes<Stack: StackInspectTr>,
            H: HostExt + ContextTr + JournalInspectTr + ?Sized,
        >(
            context: InstructionContext<'_, H, WIRE>,
        ) {
            let spec = context.interpreter.runtime_flag.spec_id();
            let Some(to) = context.interpreter.stack.inspect::<1>() else {
                context.interpreter.halt(InstructionResult::StackUnderflow);
                return;
            };
            let to = to.into_address();
            let mega_spec = context.host.spec_id();
            let storage_address: Address = $storage_addr;
            let Ok(storage_account) =
                context.host.inspect_account_delegated(mega_spec, storage_address)
            else {
                context.interpreter.halt(InstructionResult::FatalExternalError);
                return;
            };
            let is_empty = storage_account.state_clear_aware_is_empty(spec);
            let has_transfer = if $has_transfer_logic {
                let Some(value) = context.interpreter.stack.inspect::<2>() else {
                    context.interpreter.halt(InstructionResult::StackUnderflow);
                    return;
                };
                !value.is_zero()
            } else {
                false
            };
            if is_empty && has_transfer {
                let Some(new_account_storage_gas) =
                    context.host.new_account_storage_gas(storage_address)
                else {
                    context.interpreter.halt(InstructionResult::FatalExternalError);
                    return;
                };
                gas!(context.interpreter, new_account_storage_gas);
            }
            run_inner_instruction_or_abort!($wrapped_fn, context);
        }
    };
}

wrap_call_with_storage_gas!(call,          "CALL",         compute_gas_ext::call,          true);
wrap_call_with_storage_gas!(delegate_call, "DELEGATECALL", compute_gas_ext::delegate_call, false);
wrap_call_with_storage_gas!(static_call,   "STATICCALL",   compute_gas_ext::static_call,   false);
wrap_call_with_storage_gas!(
    call_code, "CALLCODE", compute_gas_ext::call_code, true,
    if mega_spec.is_enabled(MegaSpecId::REX5) {
        context.interpreter.input.target_address()
    } else {
        to
    }
);

Trade-off: the macro grows one knob (and a touch more macro-magic), but ~60 lines of duplicated logic go away and CALL/CALLCODE/DELEGATECALL/STATICCALL stay in lockstep on the shared parts. The CALLCODE-specific rationale (why the storage address differs) can stay as a comment at the invocation site.

Not blocking — happy to leave as-is if you prefer the explicit form.

[TroublorBot]

🔧 Pushed CI fixes.

Agent log

[TroublorBot]

The Codecov report is a success notification — all modified lines are covered and project coverage is 91.4%, above the threshold. No action required.

[claude]

The open CHANGES_REQUESTED from @Troublor (macro refactoring) has not been addressed in the latest push — the TroublorBot CI-fix push has an empty agent log, so nothing substantive changed. Either implement the refactor or resolve the review so the PR can progress.

One gap in the error-path coverage worth closing: the two FatalExternalError branches in call_code are tested only via Rex4 paths (code-source = EMPTY_TARGET). Under Rex5, storage_address = target_address() = CALLEE — since CALLEE always has code, state_clear_aware_is_empty is invariably false and the if is_empty && has_transfer block is never entered, so the new_account_storage_gas error branch is semantically unreachable. The inspect_account_delegated failure branch, however, is reachable under Rex5 (a DB error on CALLEE itself would trigger it) but is not currently tested. A test mirroring test_callcode_db_error_on_inspect_account but using REX5 and fail_on_account = Some(CALLEE) would cover it.

Everything else — the fix semantics, backward-compat gating, and doc update — was covered in the prior review.

[TroublorBot]

❌ I was unable to process this feedback. A human should take a look.

[TroublorBot]

🔍 Looking into this...

[claude]

The macro refactoring requested by @Troublor (parameterising wrap_call_with_storage_gas! with an address-selector) has been done in the latest commit (6cf68ec). That resolves the CHANGES_REQUESTED concern.

One gap remains unaddressed from the prior review: the inspect_account_delegated failure branch under Rex5 is not tested.

Under Rex5, storage_address = target_address() = CALLEE (the executing contract). If the database returns an error when that account is loaded, the instruction halts with FatalExternalError. The existing test_callcode_db_error_on_inspect_account only covers Rex4 (storage_address = EMPTY_TARGET). A mirror test using MegaSpecId::REX5 with db.fail_on_account = Some(CALLEE) would close this branch.

Note: the new_account_storage_gas salt-error path is correctly absent for Rex5 — CALLEE always has code so is_empty is always false and that branch is never entered. Only the inspect_account_delegated failure path is missing.

Everything else looks good — fix is semantically correct, backward-compat gating is right, and the four functional regression tests are solid.

[claude]

The inspect_account_delegated failure path under Rex5 isn't covered. Under Rex5, storage_address = CALLEE; a DB error on that lookup triggers FatalExternalError — the same path this test exercises under Rex4 for EMPTY_TARGET.

Suggested change

	#[test]
	}
	/// When `inspect_account_delegated` fails during CALLCODE under Rex5, the EVM should
	/// halt with `FatalExternalError`. Under Rex5, `storage_address = target_address() = CALLEE`.
	#[test]
	fn test_rex5_callcode_db_error_on_inspect_account() {
	let bytecode = callcode_bytecode(EMPTY_TARGET);
	let inner_db = MemoryDatabase::default()
	.account_balance(CALLER, U256::from(1_000_000_000_000u64))
	.account_balance(CALLEE, U256::from(1_000_000_000u64))
	.account_code(CALLEE, bytecode);
	let mut db = ErrorInjectingDatabase::new(inner_db);
	db.fail_on_account = Some(CALLEE);
	let result = transact_with_error_db(MegaSpecId::REX5, db, CALLER, CALLEE, 1_000_000);
	match result {
	Err(EVMError::Custom(msg)) => {
	assert!(
	msg.contains("injected basic()"),
	"error message should contain injected error, got: {msg}"
	);
	}
	Err(other) => panic!("expected EVMError::Custom, got: {other:?}"),
	Ok(result) => panic!("expected error, got success: {:?}", result.result),
	}

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[claude]

The macro refactoring requested by @Troublor has been implemented — $select_addr parameter in wrap_call_with_storage_gas! cleanly separates the address selection strategy, and all four call variants stay in lockstep on the shared logic. That CHANGES_REQUESTED concern is resolved.

One doc bug in the new tests: the comment on test_rex5_callcode_db_error_on_inspect_account says the function returns EVMError::Custom, but the test asserts EVMError::Database. The assertion is correct — db.fail_on_account = Some(CALLEE) fires during transaction setup (loading CALLEE's bytecode), before any instruction executes, so the error propagates as EVMError::Database at the outer level rather than through the FatalExternalError path inside call_code. The first three lines of that comment block (about the SALT environment failing) also appear to describe test_callcode_salt_error_on_new_account_storage_gas, not this test. The comment should be cleaned up to accurately describe what the test actually exercises.

Everything else — the fix semantics, backward-compat gating, doc update, and the four functional regression tests — remains solid. LGTM modulo the comment cleanup.

[claude]

This doc comment has two issues:

1. The first three lines describe the SALT-error path (test_callcode_salt_error_on_new_account_storage_gas), not this test — they appear to have been accidentally merged into this block.
2. Line 4–5 say the function returns EVMError::Custom, but the test asserts EVMError::Database. The assertion is correct: db.fail_on_account = Some(CALLEE) fires at transaction setup (loading CALLEE's bytecode before any instruction runs), so the error surfaces as EVMError::Database at the outer level, not through the FatalExternalError → EVMError::Custom path inside call_code.

The comment should be rewritten to accurately describe what this test exercises.

[TroublorBot]

🔍 Looking into this...

[claude]

LGTM. All prior review feedback has been addressed:

• @Troublor's macro-refactor request: done — $select_addr parameter in wrap_call_with_storage_gas! keeps all four call variants in lockstep.
• Missing Rex5 inspect_account_delegated error path test: covered by test_rex5_callcode_db_error_on_inspect_account.
• Comment accuracy: the EVMError::Database wording in that test's doc comment matches the assertion correctly.

Fix is semantically sound (CALLCODE executes in the caller's storage context, so new-account metering against the caller is the right address), backward-compat gating is correct, and test coverage is thorough.

[TroublorBot]

The @claude[bot] comment is a clean LGTM — all prior feedback has been addressed and no further changes are requested. No action needed.

[TroublorBot]

Added the missing bullet to the REX5 section of docs/spec/hardfork-spec.md and committed as ddfd4e7. The file was already Prettier-clean so no formatting changes were needed.

[TroublorBot]

The Codecov report is a success notification — all modified lines are covered and project coverage is 91.5%, above the threshold. No action required.

[claude]

LGTM. All prior review feedback has been addressed:

• @Troublor's macro refactoring — done. The $select_addr parameter in wrap_call_with_storage_gas! keeps CALL/CALLCODE/DELEGATECALL/STATICCALL in lockstep on shared logic, with storage_addr_from_to as the default and storage_addr_for_callcode providing the Rex5/pre-Rex5 split cleanly.
• Fix semantics — correct. Under Rex5, storage_addr_for_callcode returns target_address() (the executing contract / caller), which is always non-empty, so no spurious new-account storage gas is charged. Pre-Rex5 freezes the original behavior.
• Test coverage — four functional regression tests (Rex5/Rex4 × CALLCODE/CALL) plus error-path tests for DB failure and salt failure.
• Doc — hardfork-spec.md bullet and the detailed rex5.md section (numbered correctly as §6) are both present and accurate.

@Troublor — the refactoring you requested has been implemented; please dismiss your CHANGES_REQUESTED so this can merge.

[TroublorBot]

Both comments are informational — the Codecov report confirms 100% patch coverage at 91.5% project coverage, and the claude bot summary confirms all review feedback has been addressed. No action required.