debug_traceCall returning inaccurate gasUsed when both blockOverrides and stateOverrides are used

[Bitwise0x]

System information
Geth 1.14.5
Go Version: go1.22.4

The gas returned from debug_traceCall with stateOverrides often resulting inaccuracy when trying to simulate for the next block. Over estimating in all the cases. Am I missing something?

``` ` // Adding 12 seconds to the current timestamp
nextBlockTime = header.Time + 12
tx := request{To: transaction.To().Hex(), From: from.Hex(), Value: fmt.Sprintf("0x%x", transaction.Value()), Gas: fmt.Sprintf("0x%x", transaction.Gas()), GasPrice: "0x" + transaction.GasFeeCap().Text(16),Data: hexutil.Encode(transaction.Data())}
	params := make(map[string]interface{})
	params[]"tracer"] = "callTracer"
	params["tracerConfig"] = tracerConfig{OnlyTopCall: true}
        params["blockOverrides"] = make(map[string]interface{})
	params["blockOverrides"].(map[string]interface{})["number"] = "0x" + nextBlock.Text(16)
	params["blockOverrides"].(map[string]interface{})["time"] = fmt.Sprintf("0x%x", nextBlockTime)
	if overrides != nil {
		params["stateOverrides"] = make(map[string]interface{})
		switch stateoverride := params["stateOverrides"].(type) {
		case map[string]interface{}:
			for key, value := range overrides {
				stateoveride[key] = make(map[string]interface{})
				switch statediff := stateoveride[key].(type) {
				case map[string]interface{}:
					statediff["stateDiff"] = make(map[string]string)
					statediff["stateDiff"] = value
				}
			}
		}
	}
gClient.Call(&result, "debug_traceCall", tx, "latest", params)``

[Bitwise0x]

@karalabe @rjl493456442 @holiman

[s1na]

The gas returned is how much gas was used during the simulation. It is not necessarily a good estimate for submitting the tx. For that you should rather use eth_estimateGas.

Otherwise if it is inaccurate it helps if you demonstrate what you expect and what is returned.

[Bitwise0x]

@s1na
Why is debug_traceCall not accurate when both stateOverrides and blockOverrides are used within the same call? I am trying to simulate my transaction beneath another transaction, and was expecting an accurate gasUsed.

debug_traceCall with just blockOverrides works perfectly. however, when combined with stateOverrides, it overestimates gas usage by approximately 5-15k.

[s1na]

@Bitwise0x This is a difficult question to answer. You are modifying the state, that can change the flow of execution and require a different amount of gas. When submitting on chain the state might not be the same as in your override though.

Ideally you give me something to reproduce.