What should Go ABI.Pack argument type look like compared to solidity function?

Question

The following code is a popular Solidity Ethereum function

function: swapExactETHForTokens(uint256 amountOutMin, address[] path, address to, uint256 deadline)

What should amountOutMin type look like in Go?

Here is what I tried in Go:

amountOutMin := 20
data, err := routerABI.Pack("swapExactETHForTokens", amountOutMin, path, to, deadline)

The error message:

cannot use int as type ptr as argument

It is showed that amountOutMin is a pointer, while solidity's declaration is uint256. very confusing

EDIT:

minimal reproducible example

package main

import (
    "fmt"
    "log"
    "strings"
    "time"

    "github.com/ethereum/go-ethereum/accounts/abi"
    "github.com/ethereum/go-ethereum/common"
)

const (
    WETH           = "0xb4fbf271143f4fbf7b91a5ded31805e42b2208d6"
    tokenWanted    = "0x2aC3c1d3e24b45c6C310534Bc2Dd84B5ed576335"
)


func main() {

    now := time.Now()
    deadline := now.Add(10*time.Minute).Unix()

    tokenWantedAddress := common.HexToAddress(tokenWanted)
    wethTokenAddress := common.HexToAddress(WETH)
    path := []common.Address{wethTokenAddress, tokenWantedAddress}

    // random account
    activeAccountAddress := common.HexToAddress("0xb5Ca6Fd57fb9da23d0bEAE14A6349820518ea3fF")

    // copy from the following
    // https://goerli.etherscan.io/address/0x7a250d5630b4cf539739df2c5dacb4c659f2488d#code
    // Contract Name: UniswapV2Router02
    // function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
    ABI := "[{\"inputs\":[{\"internalType\":\"address\",\"name\":\"_factory\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"_WETH\",\"type\":\"address\"}],\"stateMutability\":\"nonpayable\",\"type\":\"constructor\"},{\"inputs\":[],\"name\":\"WETH\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"tokenA\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"tokenB\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"amountADesired\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountBDesired\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountAMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountBMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"addLiquidity\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountA\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountB\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"token\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenDesired\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETHMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"addLiquidityETH\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountToken\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETH\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"}],\"stateMutability\":\"payable\",\"type\":\"function\"},{\"inputs\":[],\"name\":\"factory\",\"outputs\":[{\"internalType\":\"address\",\"name\":\"\",\"type\":\"address\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveOut\",\"type\":\"uint256\"}],\"name\":\"getAmountIn\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"}],\"stateMutability\":\"pure\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveOut\",\"type\":\"uint256\"}],\"name\":\"getAmountOut\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"}],\"stateMutability\":\"pure\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"}],\"name\":\"getAmountsIn\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"}],\"name\":\"getAmountsOut\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountA\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveA\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"reserveB\",\"type\":\"uint256\"}],\"name\":\"quote\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountB\",\"type\":\"uint256\"}],\"stateMutability\":\"pure\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"tokenA\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"tokenB\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountAMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountBMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"removeLiquidity\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountA\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountB\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"token\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETHMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"removeLiquidityETH\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountToken\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETH\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"token\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETHMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"removeLiquidityETHSupportingFeeOnTransferTokens\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountETH\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"token\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETHMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"},{\"internalType\":\"bool\",\"name\":\"approveMax\",\"type\":\"bool\"},{\"internalType\":\"uint8\",\"name\":\"v\",\"type\":\"uint8\"},{\"internalType\":\"bytes32\",\"name\":\"r\",\"type\":\"bytes32\"},{\"internalType\":\"bytes32\",\"name\":\"s\",\"type\":\"bytes32\"}],\"name\":\"removeLiquidityETHWithPermit\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountToken\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETH\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"token\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountTokenMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountETHMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"},{\"internalType\":\"bool\",\"name\":\"approveMax\",\"type\":\"bool\"},{\"internalType\":\"uint8\",\"name\":\"v\",\"type\":\"uint8\"},{\"internalType\":\"bytes32\",\"name\":\"r\",\"type\":\"bytes32\"},{\"internalType\":\"bytes32\",\"name\":\"s\",\"type\":\"bytes32\"}],\"name\":\"removeLiquidityETHWithPermitSupportingFeeOnTransferTokens\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountETH\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"address\",\"name\":\"tokenA\",\"type\":\"address\"},{\"internalType\":\"address\",\"name\":\"tokenB\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"liquidity\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountAMin\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountBMin\",\"type\":\"uint256\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"},{\"internalType\":\"bool\",\"name\":\"approveMax\",\"type\":\"bool\"},{\"internalType\":\"uint8\",\"name\":\"v\",\"type\":\"uint8\"},{\"internalType\":\"bytes32\",\"name\":\"r\",\"type\":\"bytes32\"},{\"internalType\":\"bytes32\",\"name\":\"s\",\"type\":\"bytes32\"}],\"name\":\"removeLiquidityWithPermit\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"amountA\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountB\",\"type\":\"uint256\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapETHForExactTokens\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"payable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactETHForTokens\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"payable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactETHForTokensSupportingFeeOnTransferTokens\",\"outputs\":[],\"stateMutability\":\"payable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactTokensForETH\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactTokensForETHSupportingFeeOnTransferTokens\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactTokensForTokens\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountIn\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountOutMin\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapExactTokensForTokensSupportingFeeOnTransferTokens\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountInMax\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapTokensForExactETH\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"amountOut\",\"type\":\"uint256\"},{\"internalType\":\"uint256\",\"name\":\"amountInMax\",\"type\":\"uint256\"},{\"internalType\":\"address[]\",\"name\":\"path\",\"type\":\"address[]\"},{\"internalType\":\"address\",\"name\":\"to\",\"type\":\"address\"},{\"internalType\":\"uint256\",\"name\":\"deadline\",\"type\":\"uint256\"}],\"name\":\"swapTokensForExactTokens\",\"outputs\":[{\"internalType\":\"uint256[]\",\"name\":\"amounts\",\"type\":\"uint256[]\"}],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"stateMutability\":\"payable\",\"type\":\"receive\"}]"
    routerABI, err := abi.JSON(strings.NewReader(ABI))


    amountOutMin := 20  // <- Error

    data, err := routerABI.Pack("swapExactETHForTokens", amountOutMin, path, activeAccountAddress, deadline)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(data)

}

run the above code with

go run main.go

would show the error message

abi: cannot use int64 as type ptr as argument

Please can you help me figure this out?

blackgreen · Accepted Answer · 2021-07-01T17:14:10.120

It expects *big.Int types (from the math/big package)

    // ...
    amountOutMin := &big.Int{}
    amountOutMin.SetInt64(20)

    deadline := &big.Int{}
    deadline.SetInt64(time.Now().Add(10*time.Minute).Unix())

    data, err := routerABI.Pack("swapExactETHForTokens", amountOutMin, path, activeAccountAddress, deadline)

If you dig deep into the library code with a debugger, you'll eventually come to this point. This is where the error is produced:

// file: accounts/abi/type.go
func (t Type) pack(v reflect.Value) ([]byte, error) {
    // dereference pointer first if it's a pointer
    v = indirect(v)
    if err := typeCheck(t, v); err != nil {
        return nil, err
    }
    // ...

And indirect() function:

// indirect recursively dereferences the value until it either gets the value
// or finds a big.Int
func indirect(v reflect.Value) reflect.Value {
    if v.Kind() == reflect.Ptr && v.Elem().Type() != reflect.TypeOf(big.Int{}) {
        return indirect(v.Elem())
    }
    return v
}

It makes sense that the Solidity uint256 type is represented in Go with big.Int as in Go the maximum predeclared bit size is 64.

I couldn't find a reference to this in official go-ethereum documentation, but the code speaks for itself.

PS: in case you had any doubts, don't use big.Int values instead of pointers. Copying big.Int is explicitly discouraged:

To "copy" an Int value, an existing (or newly allocated) Int must be set to a new value using the Int.Set method; shallow copies of Ints are not supported and may lead to errors.

What should Go ABI.Pack argument type look like compared to solidity function?

1 Answers1