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Update EIP-7793: Clarify TXINDEX stack encoding and uint64 sentinel semantics #10795

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Update EIP-7793: Clarify TXINDEX stack encoding and uint64 sentinel semantics #10795

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4 changes: 2 additions & 2 deletions EIPS/eip-7793.md
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Expand Up @@ -39,7 +39,7 @@ We introduce a new type of [EIP-2718](./eip-2718.md) transaction, "conditional t

The fields `chain_id`, `nonce`, `max_priority_fee_per_gas`, `max_fee_per_gas`, `gas_limit`, `to`, `value`, `data`, `access_list`, `max_fee_per_blob_gas` follow the same semantics as [EIP-4844](./eip-4844.md). The field `blob_versioned_hashes` is the same except that the list may be empty for a conditional transaction.

The fields `conditional_slot` and `conditional_tx_index` are both `uint64` and specify the slot and transaction index in which this transaction should be considered valid respectively. In order to verify that `conditional_slot` is correct, [EIP-7843](./eip-7843.md) is a dependency, as this adds the slot number to the header. For both fields `-1` is used as a sentinel value for which the slot or transaction index check will not take place.
The fields `conditional_slot` and `conditional_tx_index` are both `uint64` and specify the slot and transaction index in which this transaction should be considered valid respectively. In order to verify that `conditional_slot` is correct, [EIP-7843](./eip-7843.md) is a dependency, as this adds the slot number to the header. For both fields, the sentinel value is `0xffffffffffffffff` (`2^64 - 1`). When interpreted on the EVM stack or by EVM opcodes (e.g., via `TXINDEX`), this 64-bit sentinel value MUST be zero-extended to a 256-bit stack word. If a field equals this sentinel, the corresponding check (slot or transaction index) MUST NOT take place.

#### Signature

Expand All @@ -53,7 +53,7 @@ A new opcode `TXINDEX` is introduced at `TXINDEX_OPCODE_BYTE`.

#### Output

One element `TransactionIndex` is added to the stack. `TransactionIndex` is a `uint64` in big endian encoding. It is equal to `conditional_tx_index` if the current transaction is a conditional transaction, and `-1` otherwise.
One element `TransactionIndex` is pushed to the EVM stack as a 256-bit word. The numeric value is a 64-bit unsigned integer encoded in big-endian and zero-extended to 256 bits (left-padded with zeros to 32 bytes). If the current transaction is a conditional transaction, the value equals `conditional_tx_index`. Otherwise, the value equals the 64-bit sentinel `0xffffffffffffffff` (`2^64 - 1`), zero-extended to 256 bits.

#### Gas Cost

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