Does revm provide a debugger or API for EVM bytecode?

[Taolaw]

As mentioned in the title, in some cases, I need to understand the execution of my smart contracts. I want to step through the bytecode execution line by line in a debugger, but I haven’t found any ready-made tools or APIs in revm that support this functionality. Shouldn’t this be a feature that an EVM should inherently support?

[sorpaas]

Yes we support two methods for inspection.

• Stepping: which will run a single opcode and return. The whole state is then be available for inspection. Call stack (or commonly called "call frame" in other implementations) are properly handled. See an example in jsontests: https://github.com/rust-ethereum/evm/blob/master/jsontests/src/run.rs#L245
• Inspection: you can directly "wrap" an existing Etable which will give you the environment exactly as when an opcode is executing, and log any data that opcode can see. (Gasometer in Rust EVM is actually just a wrapped Etable.) We don't have a complete example yet, but for now see: https://github.com/rust-ethereum/evm/blob/master/interpreter/tests/usability.rs#L46 and please stay tuned as we're working on more docs. 😃