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Overview

Opcode: 0x3a Introduced: Frontier (EVM genesis) GASPRICE pushes the gas price of the current transaction onto the stack, measured in wei per gas unit.

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Specification

Stack Input: 
[]
Stack Output: 
gasPrice (uint256, wei per gas)
Gas Cost: 2 (GasQuickStep) Operation: 
stack.push(transaction.gasPrice)

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Behavior

Returns the gas price specified in the transaction. For EIP-1559 transactions, this is the effective gas price (baseFee + priorityFee). Key characteristics:
  • Same value throughout transaction
  • In wei per gas unit
  • For EIP-1559: min(baseFee + maxPriorityFeePerGas, maxFeePerGas)
  • For legacy: transaction’s gasPrice field

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Examples

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Basic Usage

import { gasprice } from '@tevm/voltaire/evm/context';
import { createFrame } from '@tevm/voltaire/evm/Frame';

const frame = createFrame({ stack: [] });
const txGasPrice = 20_000_000_000n; // 20 gwei

const err = gasprice(frame, txGasPrice);

console.log(frame.stack[0]); // 20000000000n

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Gas Refunds

contract GasRefunder {
    function expensiveOperation() public {
        uint256 startGas = gasleft();

        // ... expensive operations ...

        uint256 gasUsed = startGas - gasleft();
        uint256 refund = gasUsed * tx.gasprice;

        payable(msg.sender).transfer(refund);
    }
}

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Gas Price Oracle

contract GasPriceTracker {
    uint256[] public recentPrices;

    function record() public {
        recentPrices.push(tx.gasprice);
    }

    function averagePrice() public view returns (uint256) {
        uint256 sum = 0;
        for (uint i = 0; i < recentPrices.length; i++) {
            sum += recentPrices[i];
        }
        return sum / recentPrices.length;
    }
}

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Gas Cost

Cost: 2 gas (GasQuickStep)

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Common Usage

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Transaction Cost Calculation

function estimateCost(uint256 gasEstimate) public view returns (uint256) {
    return gasEstimate * tx.gasprice;
}

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Minimum Gas Price

modifier minGasPrice(uint256 min) {
    require(tx.gasprice >= min, "Gas price too low");
    _;
}

function urgentOperation() public minGasPrice(50 gwei) {
    // Only execute if gas price >= 50 gwei
}

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Security

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EIP-1559 Considerations

Post-EIP-1559, tx.gasprice is effective gas price, not maxFeePerGas: 
// Block baseFee = 30 gwei
// maxPriorityFeePerGas = 2 gwei
// maxFeePerGas = 100 gwei
// tx.gasprice = 32 gwei (30 + 2)

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Gas Price Manipulation

Don’t use tx.gasprice for critical logic - miners can manipulate it.

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Implementation

import { consumeGas } from "../Frame/consumeGas.js";
import { pushStack } from "../Frame/pushStack.js";

/**
 * GASPRICE opcode (0x3a) - Get transaction gas price
 *
 * Stack: [] => [gasPrice]
 * Gas: 2 (GasQuickStep)
 */
export function gasprice(
  frame: FrameType,
  gasPrice: bigint
): EvmError | null {
  const gasErr = consumeGas(frame, 2n);
  if (gasErr) return gasErr;

  const pushErr = pushStack(frame, gasPrice);
  if (pushErr) return pushErr;

  frame.pc += 1;
  return null;
}

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References