Inspired by evm-tools. (But this project has stopped development and is now unable to compile).

This is a guide to understanding the EVM, its relationship with solidity, and how to use some debugging tools.

Requirements

• evm has been tested and is known to run on Linux/Ubuntu, macOS and Windows(10). It will likely work fine on most OS.
• Go 1.11 or newer.

Installation

go get github.com/mohanson/evm/cmd/evm

Feat: disassemble bytecode

Here is some very simple bytecode I wrote:

0x6005600401

To disassemble, run evm disasm -code 0x6005600401, which produces:

[0000] PUSH1 0x05
[0002] PUSH1 0x04
[0004] ADD

Feat: execute bytecode

Let's use a test case to demonstrate: return0.json. To execute the test, run

$ evm exec -code 0x603760005360005160005560016000f3

[Many Outputs]
...

Return  = 0x37

Perfect!

Feat: execute solidity

Let us begin with the most basic example. It is fine if you do not understand everything right now, we will go into more detail later. Create a file named "SimpleStorage.sol" with content:

pragma solidity ^0.4.24;

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() view public returns (uint) {
        return storedData;
    }
}

Use solc to compile it to bytecode:

$ solc --bin SimpleStorage.sol

# The output bytecode. I will use the $BYTECODE to instead of the original text.
608060405234801561001057600080fd5b5060df8061001f6000396000f3006080604052600436106049576000357c0100000000000000000000000000000000000000000000000000000000900463ffffffff16806360fe47b114604e5780636d4ce63c146078575b600080fd5b348015605957600080fd5b5060766004803603810190808035906020019092919050505060a0565b005b348015608357600080fd5b50608a60aa565b6040518082815260200191505060405180910390f35b8060008190555050565b600080549050905600a165627a7a7230582099c66a25d59f0aa78f7ebc40748fa1d1fbc335d8d780f284841b30e0365acd960029

# create it at /tmp/db.json.
$ evm create -db /tmp/db.json
             -data $BYTECODE

Cost    = 55307
Address = 0xBd770416a3345F91E4B34576cb804a576fa48EB1

# let's call SimpleStorage.set(42)
$ evm call -db /tmp/db.json
           -address 0xBd770416a3345F91E4B34576cb804a576fa48EB1
           -data 0x60fe47b1000000000000000000000000000000000000000000000000000000000000002a

# let's call SimpleStorage.get()
$ evm call -db /tmp/db.json
           -address 0xBd770416a3345F91E4B34576cb804a576fa48EB1
           -data 0x6d4ce63c

Cost    = 424
Return  = 000000000000000000000000000000000000000000000000000000000000002a

Perfect!

---

Note: data 0x60fe47b1000000000000000000000000000000000000000000000000000000000000002a = 0x60fe47b1 + 0x2a, where 60fe47b1 provided by python -c "import eth_utils; print(eth_utils.keccak(b'set(uint256)')[0:4].hex())".