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# Debugging Panda Safety with Replay Drive + LLDB
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By default, `libsafety.so` is built with optimizations and stripped symbols, which makes C-level debugging impractical.
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This workflow fixes that by:
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1. Building `libsafety` with debug symbols and no optimizations.
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2. Running `replay_drive.py` with a user-provided route.
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3. Attaching LLDB automatically from VS Code.
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---
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## Building with Debug Symbols
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Rebuild `libsafety` with the `--unoptimized` flag:
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```bash
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scons -u -j$(nproc) --unoptimized
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```
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This enables the debug flags:
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* `-g` (include symbols)
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* `-O0` (disable optimizations)
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* `-fno-omit-frame-pointer` (keep stack traces usable)
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---
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## Debugging Workflow
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1. **Build with debug symbols**
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```bash
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scons -u -j$(nproc) --unoptimized
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```
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2. **Start the debugger in VS Code**
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* Select **Replay drive + Safety LLDB**.
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* Enter the route or segment when prompted.
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3. **Attach LLDB**
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* When prompted, pick the running **`replay_drive` process**.
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* ⚠️ Attach quickly, or `replay_drive` will start consuming messages.
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✅ Tip: Add a Python breakpoint at the start of `replay_drive.py` to pause execution and give yourself time to attach LLDB.
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4. **Set breakpoints in VS Code**
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Breakpoints can be set directly in `libsafety.c` (or any C file).
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No extra LLDB commands are required — just place breakpoints in the editor.
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5. **Resume execution**
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Once attached, you can step through both Python and C safety code as CAN logs are replayed.
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---
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## Notes
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* Always rebuild with `--unoptimized` before debugging.
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* Use short routes for quicker iteration.
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* Pause `replay_drive` early to avoid wasting log messages.
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### Video
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[demo safety debug.mp4](assets/demo%20safety%20debug.mp4)
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