soldb-repl 0.1.0

Interactive debugger state machine (breakpoints, stepping, display modes) for SolDB
Documentation

SolDB – ETHDebug-First Solidity Debugger

CI License: GPL v3 or MIT Rust

Note: SolDB is in public beta; expect ongoing changes and occasional inaccuracies.

Note: SolDB relies on compiler-generated debug metadata. ETHDebug gives the richest breakpoints, stepping, and variable views; legacy source maps provide source-level fallback.

SolDB is an open-source, ETHDebug-first, LLDB-style debugger for Solidity and the EVM.

soldb demo 11 sept 2025

Quick Start

Install SolDB:

cargo install soldb

Optional debug-adapter binary:

cargo install soldb-dap

To track the development branch instead, install from git:

cargo install --git https://github.com/walnuthq/soldb.git soldb

Run against a local node (Anvil):

anvil --steps-tracing

Compile your contracts with ETHDebug (Solidity 0.8.29+):

solc --via-ir --debug-info ethdebug --ethdebug --ethdebug-runtime --bin --abi --overwrite -o out examples/Counter.sol

Legacy source maps are also accepted. For example, compile with Solar using -g source-maps --emit=abi,bin,bin-runtime --out-dir out; SolDB reads combined.json when ETHDebug programs are absent.

Trace a transaction:

soldb trace <tx_hash> --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545

Force the replay backend when you want to avoid debug_traceTransaction:

soldb trace <tx_hash> --backend replay --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545

Profile dynamic gas by contract, function, and source line, with an optional interactive SVG flame graph:

soldb profile <tx_hash> --backend replay \
  --ethdebug-dir <contract_address>:<contract_name>:./out \
  --rpc http://localhost:8545 --flamegraph profile.svg

See docs/profiling.md for captured traces, folded stacks, multi-contract attribution, and the reusable library API.

Example: Debugging a Transaction

soldb trace 0x2832...3994 --ethdebug-dir 0x3aa5ebb10dc797cac828524e59a333d0a371443c:TestContract:./out --rpc http://localhost:8545

Output:

Contract: TestContract
Gas used: 50835
Status: SUCCESS

Call Stack:
#0 TestContract::runtime_dispatcher [entry] @ TestContract.sol:1
  #1 increment [external] gas: 29241 @ TestContract.sol:23
    #2 increment2 [internal] gas: 6322 @ TestContract.sol:39
      #3 increment3 [internal] gas: 5172 @ TestContract.sol:54

Interactive mode:

soldb trace <tx_hash> --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545 --interactive

Inside REPL:

soldb> break TestContract.sol:42
soldb> next
soldb> print balance

Example: Simulating a Contract Call

Test contract functions without sending transactions on chain.

soldb simulate <contract_address> "increment(uint256)" 10 --from <sender_address> --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545

Output containing a simulation failure:

Contract: TestContract
Gas used: 27157
Status: REVERTED
Error: Value must be even

Call Stack:
#0 TestContract::runtime_dispatcher [entry] @ TestContract.sol:1
  #1 increment [external] gas: 20835 @ TestContract.sol:23 
    #2 isEven [internal] gas: 6322 @ TestContract.sol:38 !!!

You can also pass complex types (structs, tuples):

soldb simulate <contract_address> "submitPerson((string,uint256))" '("Alice", 30)'     --from <sender_address>     --ethdebug-dir <contract_address>:<contract_name>:./out     --rpc http://localhost:8545

You can also debug simulations interactively using the --interactive flag:

soldb simulate <contract_address> "increment(uint256)" 5     --from <sender_address>     --ethdebug-dir <contract_address>:<contract_name>:./out     --rpc http://localhost:8545     --interactive

Inside REPL:

soldb> break TestContract.sol:38
soldb> step
soldb> vars

Gas Profiling

soldb profile attributes dynamic EVM gas to contracts, functions, source lines, opcodes, and instructions using compiler-generated debug metadata. It can also generate an interactive flame graph. Legacy source maps retain exact source-line attribution but do not carry ETHDebug function identities.

SolDB gas profile flame graph

See the profiling guide for usage and integration details.

Features

  • ETHDebug-first source debugging with legacy srcmap/srcmap-runtime fallback
  • Source-level variable inspection (vars, print <name>) in both the REPL and the DAP server, decoded from ETHDebug variable locations
  • Full transaction traces with internal calls & decoded parameters
  • Dynamic gas profiles by contract, function, source line, opcode, and instruction
  • Folded-stack and interactive SVG flame graph output
  • Transaction simulation with arbitrary calldata (including structs & tuples)
  • Interactive LLDB-like REPL (step, break, print, etc.) – works for both transactions and simulations
  • HTTP/HTTPS JSON-RPC transport with debug-RPC tracing and normal-RPC replay for local Anvil transactions
  • Interop-ready tracing for Ethereum environments that combine EVM contracts with other VMs

Architecture

SolDB is split into focused crates so RPC transport, ETHDebug parsing, execution backends, CLI presentation, and interactive debugging can evolve independently.

flowchart TD
    contracts["Solidity contracts"] --> solc["solc<br/>--debug-info ethdebug<br/>--ethdebug --ethdebug-runtime"]
    solc --> artifacts["ETHDebug + ABI artifacts"]

    cli["soldb trace / simulate / profile"] --> metadata["soldb-ethdebug<br/>metadata + ABI loader"]
    artifacts --> metadata

    cli --> selector["soldb-rpc<br/>backend selector"]
    selector --> debug_rpc["debug-rpc backend<br/>debug_traceTransaction / debug_traceCall"]
    selector --> replay["replay backend<br/>normal RPC state -> REVM inspectors"]

    debug_rpc --> opcode_trace["opcode trace"]
    replay --> opcode_trace
    metadata --> debugger["soldb-debugger<br/>source steps + variables"]
    opcode_trace --> enriched
    debugger --> enriched["source lines<br/>call frames<br/>decoded values"]
    enriched --> outputs["CLI / JSON / REPL / DAP"]
    opcode_trace --> profiler["soldb-profiler<br/>gas aggregation"]
    metadata --> profiler
    profiler --> profile_outputs["tables / JSON / flame graph"]

SolDB relies on compiler-generated debug information. Pass an ETHDebug or legacy combined-JSON artifact directory with --ethdebug-dir <address>:<contract>:<dir>. ETHDebug provides source, function, variable, and ABI context; legacy source maps provide PC-to-source mapping and ABI data without inventing the missing metadata. The debugger-side ETHDebug contract is documented in docs/ethdebug-debugger-contract.md.

The --json output for trace and simulate is versioned for web and explorer integrations. See docs/json.md for the current schema, capability flags, replay artifacts, and compatibility rules.

Execution Backends

The trace command supports three backend modes:

  • auto (default): tries debug-rpc first, then falls back to replay when the node reports that debug_traceTransaction is unavailable.
  • debug-rpc: calls debug_traceTransaction and is the fast path for Anvil, Geth, and other debug-capable nodes.
  • replay: loads transaction, receipt, parent-block state, bytecode, balances, nonces, and storage through normal Ethereum JSON-RPC, replays prior transactions in the block when needed, then replays the target transaction in REVM with inspectors. It selects the REVM spec from chain/block/timestamp for mainnet, Sepolia, Holesky, and Hoodi; archive-provider hardening and broader cache tuning are next-stage work.

Select the backend explicitly:

soldb trace <tx_hash> --backend auto --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545
soldb trace <tx_hash> --backend debug-rpc --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545
soldb trace <tx_hash> --backend replay --ethdebug-dir <contract_address>:<contract_name>:./out --rpc http://localhost:8545

Crates

  • crates/soldb-cli: command-line interface, output formatting, and command wiring.
  • crates/soldb-core: shared error types, trace models, and debugger data structures.
  • crates/soldb-rpc: JSON-RPC transport, debug-RPC backend, replay backend, transaction simulation, and event log retrieval.
  • crates/soldb-ethdebug: ETHDebug metadata loading, ABI helpers, source mapping, event decoding, and call-frame enrichment.
  • crates/soldb-debugger: reusable source-step, function, and variable decoding model shared by frontends.
  • crates/soldb-profiler: reusable gas attribution and folded-stack model over traces and ETHDebug programs.
  • crates/soldb-repl: interactive debugger state and REPL commands.
  • crates/soldb-serializer: JSON/web-facing trace and simulation serialization, including nested call trees and ETHDebug source metadata.
  • crates/soldb-compiler: solc ETHDebug compilation, deployment helpers, and auto-deploy support for local workflows.
  • crates/soldb-bridge: bridge server for cross-environment Solidity<>Stylus debugging.
  • crates/soldb-dap: Debug Adapter Protocol server for editor integrations.

Use Cases

  • Local Solidity debugging
    Step through Solidity execution, inspect variables, debug failing fuzz tests.

  • Transaction analysis
    Reproduce mainnet/testnet transactions locally, pinpoint reverts or unexpected flows.

  • Tooling integrations
    Generate full transaction traces for explorers and dev tools (already powering Walnut).

Interop

Ethereum is moving toward richer interoperability, where applications may span multiple chains, execution environments, and VMs. SolDB is designed around that direction: keep Solidity and EVM debugging grounded in compiler-generated ETHDebug metadata, while allowing other execution environments to plug into the same trace, call-stack, and debugger-output model.

The goal is for developers to debug cross-environment transactions without switching mental models at every call boundary. EVM debug-RPC and replay remain the core path for Solidity execution, and bridge integrations can attach additional VM-specific debuggers as ecosystems adopt interop patterns.

Stylus is the first integrated non-EVM environment. Additional runtimes can follow the same bridge-oriented model.

See docs/Stylus.md for the current Stylus integration.

Development

Install From Source

git clone https://github.com/walnuthq/soldb.git
cd soldb
cargo build --workspace --all-targets
cargo install --path crates/soldb-cli
cargo install --path crates/soldb-dap

Run Automated Tests

Prerequisites

  • Rust stable toolchain
  • RPC at http://localhost:8545 (Anvil default)
  • Anvil running with tracing enabled: 
    anvil --steps-tracing
  • Solidity compiler:
    • solc 0.8.29+ for ETHDebug tests
    • solc 0.8.16 for legacy source-map tests
  • LLVM tools (lit, FileCheck) 
      # Install LLVM
  # macOS
  brew install llvm
  # Ubuntu
  sudo apt-get install llvm-dev

Run unit tests:

cargo test --workspace --all-targets

Run lit end-to-end CLI tests:

./test/run-tests.sh SOLC_PATH=/path/to/solc

Run the full local test target:

make test

CI additionally runs the lit suite against solc built from the Solidity development branch, where ETHDebug output changes first. That job is non-blocking and also runs on a daily schedule. To reproduce it locally, point the runner at your own build:

./test/run-tests.sh SOLC_PATH=/path/to/solidity/build/solc/solc

Coverage

Line coverage is enforced at 80% in CI.

cargo llvm-cov --workspace --all-targets --fail-under-lines 80
make coverage

License

SolDB is dual-licensed under the GNU General Public License v3.0 or the MIT license, at your option: use, redistribute, and modify it under the terms of either one. Unless you state otherwise, contributions you submit are dual-licensed the same way.

📄 GPL-3.0 · MIT

Community & Support

📬 Email: hi@walnut.dev