# CKB debugger
A standalone debugger enabling off-chain contract development.
# Usage
For Rust library usage, refer to the included tests, they are quite self-explanatory.
See the command line help part for usage on the binary debugger:
```text
ckb-debugger 0.113.0
USAGE:
ckb-debugger [FLAGS] [OPTIONS] --mode <mode> --tx-file <tx-file> [args]...
FLAGS:
-h, --help Prints help information
--prompt Set to true to prompt for stdin input before executing
--step Set to true to enable step mode, where we print PC address for each instruction
-V, --version Prints version information
OPTIONS:
--bin <bin> File used to replace the binary denoted in the script
-i, --cell-index <cell-index> Index of cell to run
-t, --cell-type <cell-type> Type of cell to run [possible values: input, output]
--decode <decode> Decode RISC-V instruction
--dump-file <dump-file> Dump file name
--gdb-listen <gdb-listen> Address to listen for GDB remote debugging server
--gdb-specify-depth <gdb-specify-depth> Specifies the depth of the exec/spawn stack [default: 0]
--max-cycles <max-cycles> Max cycles [default: 70000000]
--mode <mode>
Execution mode of debugger [default: full] [possible values: full, fast, gdb, probe, gdb_gdbstub]
--pprof <pprof> Performance profiling, specify output file for further use
--read-file <read-file>
Read content from local file or stdin. Then feed the content to syscall in scripts
-s, --script-group-type <script-group-type> Script group type [possible values: lock, type]
--script-hash <script-hash> Script hash
--script-version <script-version> Script version [default: 2]
--skip-end <skip-end> End address to skip printing debug info
--skip-start <skip-start> Start address to skip printing debug info
-f, --tx-file <tx-file> Filename containing JSON formatted transaction dump
ARGS:
<args>...
```
[ckb-transaction-dumper](https://github.com/xxuejie/ckb-transaction-dumper) can be used to dump the full mocked transaction used in the debugger from CKB.
# FAQ
## How to Print Debug Message
1. [compile the contract via `-fno-builtin-printf` and replace with `CKB_C_STDLIB_PRINTF`](https://github.com/nervosnetwork/ckb-vm/discussions/193)
2. set `RUST_LOG=debug` to [enable](https://docs.rs/env_logger/latest/env_logger/) output [debug message](https://github.com/nervosnetwork/ckb-standalone-debugger/blob/eaeb6128837cc3103dbaa5eb61a1f49304935e5a/bins/src/main.rs#L266-L268)