trace_call

Note

Served only when trace is named in --http.api or --ws.api; see Enabling Namespaces.

Warning

Fee fields at latest and pending

At latest and pending this method prices the call against the block header’s base fee, not the worker’s current epoch base fee that eth_call and eth_estimateGas use. A request that sets gasPrice, maxFeePerGas or maxPriorityFeePerGas can therefore be accepted by eth_call and rejected here, or the reverse; requests without fee fields are unaffected. Tracked in #1587.

Executes a call on the state of a block without creating a transaction, and returns the trace types requested: the call frames, the executed instructions, the state changes, or any combination. Nothing is sent or stored.

Parameters

Object - The transaction call object, as for eth_call:

from: DATA, 20 bytes - (optional) The address the call is sent from.
to: DATA, 20 bytes - The address the call is directed to. Leave it out to simulate a contract creation.
gas: QUANTITY - (optional) The gas limit for the call. The top-level trace’s action.gas is this limit minus the call’s intrinsic gas.
gasPrice: QUANTITY - (optional) The price paid per unit of gas, for a legacy-style call.
maxFeePerGas: QUANTITY - (optional) The most, in wei, the sender pays per unit of gas, base fee and priority fee together.
maxPriorityFeePerGas: QUANTITY - (optional) The most, in wei, the sender pays per unit of gas above the base fee.
value: QUANTITY - (optional) The value sent with the call, in wei.
input: DATA - (optional) The call data. data is accepted as an alias.

Array - The trace types to return, any of "trace", "vmTrace" and "stateDiff".

QUANTITY|TAG|DATA - (optional) The block whose state the call runs on: a hexadecimal block number, a 32-byte block hash, or one of the string tags latest, earliest, safe or finalized. See the default block parameter. Defaults to latest.

Object - (optional) State overrides, keyed by account address. Each entry may set balance, nonce, code, state (replaces the account’s whole storage) or stateDiff (overrides single storage slots).

Object - (optional) Block overrides for the block the call runs in, such as number, time, gasLimit, coinbase or baseFee.

Returns

Object - The requested traces:

output: DATA - The return data of the top-level call; 0x for a plain transfer.
stateDiff: Object - With stateDiff requested, the state changes keyed by account address; otherwise null. Each account has balance, code, nonce and storage (keyed by slot). Each value is "=" when unchanged, {"+": value} when created, {"-": value} when removed, or {"*": {"from": old, "to": new}} when changed.
trace: Array - With trace requested, the call frames, top-level first; otherwise []. Each frame has type, action, error (only when the frame failed), result, subtraces and traceAddress, with the meanings trace_transaction gives them, and no block or transaction fields. The top-level frame’s action.gas and result.gasUsed leave out the intrinsic gas, so for a plain transfer with a 21,000 gas limit both are 0x0.
vmTrace: Object - With vmTrace requested, the instructions the top-level call executed; otherwise null. It has code (DATA, the code that ran) and ops, one entry per instruction with cost (Number, its gas cost), pc (Number, the program counter), ex (its effects: used, push for the stack items it pushed, mem for a memory write and store for a storage write), sub (the nested vmTrace of a CALL or CREATE, or null), and, when present, op (the opcode name) and idx.

Example

Request

curl http://localhost:8545 \
 -X POST \
 -H "Content-Type: application/json" \
 --data '{"jsonrpc":"2.0","method":"trace_call","params":[{
  "from":"0xb14d3c4f5fbfbcfb98af2d330000d49c95b93aa7",
  "to":"0x0000000000000000000000000000000000000000",
  "gas":"0x5208",
  "value":"0x64"},
  ["trace"],
  "latest"],"id":1}'

Result

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "output": "0x",
    "stateDiff": null,
    "trace": [
      {
        "type": "call",
        "action": {
          "from": "0xb14d3c4f5fbfbcfb98af2d330000d49c95b93aa7",
          "callType": "call",
          "gas": "0x0",
          "input": "0x",
          "to": "0x0000000000000000000000000000000000000000",
          "value": "0x64"
        },
        "result": {
          "gasUsed": "0x0",
          "output": "0x"
        },
        "subtraces": 0,
        "traceAddress": []
      }
    ],
    "vmTrace": null
  }
}