return msg.sender.balance; returns unexpected value

[o0ragman0o]

I'm raising this first as a Solidity issue but maybe a deeper issue present.

This was raised on SE yesterday and I have confirmed unexpected behaviour with a contract on Rinkeby

I'm using MetaMask to connect to Rinkeby and I'm deploying the contracts via Remix. When I call the function returnsenderbalance it returns

115792089237316195423570985008687907853269984665640564039456084007913129639935
rather than my balance in Wei. The code is below:

pragma solidity ^0.4.11;

contract returnbalance{
    function returnsenderbalance() constant returns (uint){
        return msg.sender.balance;  
    }
}

The return value of msg.sender.balance appears to be a unit cast negative value unassociated with the actual account balance.

Behaviour is present in Geth.
Behaviour not present in the JavascriptVM which works as expected.
Have not tested on Parity.

[axic]

This is translated into this (with 0.4.12-develop.2017.5.30+commit.64f76b30.Darwin.appleclang
):

        /* "rb.sol":78:82  uint */
      0x0
        /* "rb.sol":100:110  msg.sender */
      caller
        /* "rb.sol":100:118  msg.sender.balance */
      0xffffffffffffffffffffffffffffffffffffffff
      and
      balance
        /* "rb.sol":93:118  return msg.sender.balance */
      swap1
      pop
        /* "rb.sol":29:127  function returnsenderbalance() constant returns (uint){... */

This seems to be correct. Does it work properly with on-chain transactions? It only fails with eth_call on geth?

[kieranelby]

FWIW, I've also seen this (and been very confused by it), in my case using MetaMask to call a constant contract function that returns the balance of an address - about 50% of the time I get the correct result, other times I get 115792089237316195423570985008687907853269984665640564039455084007913129639935. Perhaps a geth/MetaMask issue - never seen with JavascriptVM.

[axic]

@o0ragman0o @kieranelby since it is not present on ethereumjs-vm, but both of you have seen it with geth, please open an issue on go-ethereum.

[o0ragman0o]

I've realised that msg.sender itself does not make sense in a constant function. The following function returns garbage under different clients.

contract ReturnSender {
    function retSenderAddr() public constant returns (address)
    {
        return msg.sender;
    }
}

[axic]

From Solidity's perspective it still makes sense, it is part of the state and constant functions can read the state, just they cannot modify it.

Since this flag is also populated in the ABI JSON, certain tools (such as web3.js) will consider those functions can be executed via eth_call, which is true, but it still requires proper values. However, they can also be executed by other contract functions, so it doesn't make sense disallowing msg.sender.

I'm not sure why sender would be omitted in eth_call though.

[o0ragman0o]

I'm not aware enough of how eth_call works. I'll raise this as a Geth issue as suggested. However, now I can't reproduce the bad behaviour returning msg.sender with other clients (local Remix may have been corrupted and I've been trying to stabilise all morning).

[mr-robek]

i'm experiencing the same behavior. my smartcontract looks like this:
function balanceOfEther(address user) public constant returns (uint256) { return user.balance; }
i deployed it to main network and every time i call it using metamask i get the same big number 11579...
caling it from etherscan "read smart contract" feature works well.
any workarounds/solution since august?

[axic]

This is still doesn't look a Solidity bug. Please report it to Metamask or any other client you are using.

[axic]

Closing this as the generated code seemed to be correct.

[diegobes]

This is related to:

eth/api_backend.go

func (b *EthAPIBackend) GetEVM(ctx context.Context, msg core.Message, state *state.StateDB, header *types.Header, vmCfg vm.Config) (*vm.EVM, func() error, error) {
===> state.SetBalance(msg.From(), math.MaxBig256)
vmError := func() error { return nil }
context := core.NewEVMContext(msg, header, b.eth.BlockChain(), nil)
return vm.NewEVM(context, state, b.eth.chainConfig, vmCfg), vmError, nil
}

math.MaxBig256 == 115792089237316195423570985008687907853269984665640564039455084007913129639935

Is a constant in Geth( common/math/big.go)