Is it possible to preload contracts in the genesis block?

Question

Here's the setup I'm trying to use:

A genesis.json with the alloc field set to include code.

"alloc": {
    "0000000000000000000000000000000000000001": {
      "code": "6060604052608f8060106000396000f360606040526000357c0100000000000000000000000000000000000000000000000000000000900480634e70b1dc14604157806360fe47b114606257603f565b005b604c60048050506078565b6040518082815260200191505060405180910390f35b607660048080359060200190919050506081565b005b60006000505481565b806000600050819055505b5056"
    }
}

Then running geth and entering (with a default account set, unlocked, and loaded):

var getAndSetContract = eth.contract([{"constant":true,"inputs":[],"name":"num","outputs":[{"name":"","type":"uint256"}],"type":"function"},{"constant":false,"inputs":[{"name":"val","type":"uint256"}],"name":"set","outputs":[],"type":"function"}])
var getAndSet = getAndSetContract.at("0000000000000000000000000000000000000001")
getAndSet.set(2, {gas: 1000000})
miner.start()
// a few blocks quickly roll in given this is on a private testing blockchain
miner.stop()
getAndSet.num()

Results in a final returned value of

3.054357634959941643970700719428062453954541146150392020568168920432276498019e+75

versus the desired

2

Here's the contract source:

contract getAndSet {
    uint public num;
    function set(uint val){
        num = val;
    }
}

This whole adventure started after coming across this line in the geth source: https://github.com/ethereum/go-ethereum/blob/290e851f57f5d27a1d5f0f7ad784c836e017c337/core/genesis.go#L56 I think I saw something about preloading contracts in the past, though I haven't been able to dig anything up. AFAIK I could be on a wild goose chase trying to make use of a half-implemented feature.

Answer 1

How did you build yor contract ? If you want to add a contract to genesis block you need to build it with solc --bin-runtime.

By default solc and ide like remix build return code that is used for creating the contract. This code returns the actual code that is stored in the blockchain

Answer 2

Your method does not return any value. Calling set() will return the transaction hash of the calling transaction. You also need to specify the account from which you are deploying the transaction:

getAndSet.set(2, {eth.accounts[0], gas: 1000000});

(make sure you have enough balance on that account).

Answer 3

I came across this old question about preloading a contract into the genesis file, so the answer is yes and for people who don't want to use solc (--bin-runtime) you can:

• Deploy your contract into your network

• get back the bytecode deployed by using (after attaching to geth)

  web3.eth.getCode("0xEc76BC7094f17fE3C987d3eb574C765219B7F1bF") "0x608060405260043610610112576000357c0100000000000000000000000000000000000000000000000000000000900463fffffff.."

NB: the bytecode returned byremix doesn't work

• copy the result into your genesis file with an address of your choice as following

  "8c7aD47113641cA92b138470620A5A39b2f7B9e8": { "code":"0x608060405260043610610112576000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff...."

• restart the network