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In order to modify GetBalance function to fork go-ethereum, I find difficulties to get a reference of the running evm. The function has a reference for self *StateDB:

func (self *StateDB) GetBalance(addr common.Address) *big.Int

but I cannot get an evm of type *vm.EVM from StateDB. I need the evm to make a contract call inside the GetBalance function for this fork. Is it possible in some way to get the evm from StateDB, or should I use any other strategy?

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    What do you want to achieve? Do you want to execute a smart contract from GetBalance? I think you can call GetBalance outside the EVM so you wont be able to get the running instance of the EVM in that case.
    – Ismael ♦
    Jun 5, 2019 at 18:23
  • Yes, I want GetBalance to call a SC whenever it is run. So I don't want to call GetBalance, but to force a SC call when go-ethereum calls GetBalance. This is why I need an EVM reference inside GetBalance scope.
    – Juan Ignacio Pérez Sacristán
    Jun 6, 2019 at 7:24

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getBalance doesn't require EVM because it only reads data in StateDB.

Therefore, it is in core/state/statedb.

I recommend creating a new instruction.

and reference other instructions changing stateDB.

for example, opStaticCall in core/vm/instruction 

func opStaticCall(pc *uint64, interpreter *EVMInterpreter, contract *Contract, memory *Memory, stack *Stack) ([]byte, error)

this function calls staticCall in core/vm/evm

func (evm *EVM) StaticCall(caller ContractRef, addr common.Address, input []byte, gas uint64) (ret []byte, leftOverGas uint64, err error)

this function include this line

evm.StateDB.AddBalance(addr, bigZero)
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  • Sorry but, this solution wouldn't allow to invoke contract call from inside getBalance, and there is where I need it to be. opStaticCall requires an interpreter *EVMInterpreter parameter I still don't have inside getBalance function.
    – Juan Ignacio Pérez Sacristán
    Jun 3, 2019 at 14:30

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