rr-debugger

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Deterministic debugging with rr record-replay. Use when debugging crashes, ASAN faults, or when reverse execution is needed. Provides reverse-next, reverse-step, reverse-continue commands and crash trace extraction.

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[Debugging]

When & Why to Use This Skill

The rr-debugger Claude skill enables deterministic record-and-replay debugging for software engineering. It allows developers to capture program execution and replay it with full reverse execution capabilities, making it possible to step backward through code to identify the root cause of complex crashes, memory corruption, and non-deterministic bugs.

Use Cases

  • 1. Root Cause Analysis for Crashes: Record a program's failure and use reverse-execution commands like 'reverse-next' and 'reverse-step' to trace back from the crash point to the specific line of code that caused the error.
  • 2. Debugging ASAN and Memory Faults: Efficiently diagnose AddressSanitizer (ASAN) faults by setting breakpoints at the fault location and stepping backward to find the exact moment of memory corruption.
  • 3. Investigating Intermittent Bugs: Capture rare race conditions or non-deterministic bugs in a recording, allowing for consistent, deterministic replay and inspection of variables and memory states at any point in time.
  • 4. Automated Execution Tracing: Utilize integrated scripts to automatically extract execution traces leading up to a crash, providing a detailed map of the program's execution path for faster resolution.
namerr-debugger
descriptionDeterministic debugging with rr record-replay. Use when debugging crashes, ASAN faults, or when reverse execution is needed. Provides reverse-next, reverse-step, reverse-continue commands and crash trace extraction.

rr Deterministic Debugger

rr provides deterministic record-replay debugging with full reverse execution capabilities.

Core Workflow

  1. Record: rr record <program> [args]
  2. Replay: rr replay (enters gdb interface with reverse execution)

Reverse Execution Commands

All standard gdb commands work, plus reverse variants:

  • reverse-next / rn: Step back over function calls
  • reverse-step / rs: Step back into functions
  • reverse-continue / rc: Continue backward to previous breakpoint
  • reverse-stepi / rsi: Step back one instruction
  • reverse-nexti / rni: Step back over one instruction

Crash Trace Extraction

Regular Crashes

After rr record <crashing-program>:

rr replay
# In gdb:
reverse-next 100    # Go back 100 steps (adjust N as needed)
# Now step forward to see execution leading to crash:
next
next
...

ASAN Crashes

After rr record <asan-program>:

rr replay
# In gdb:
bt                  # View stack trace
up                  # Issue "up" commands until last app frame (before ASAN runtime)
break *$pc          # Set breakpoint at that location
reverse-continue    # Go back to last app instruction before ASAN
# Now step forward to see execution leading to fault:
next
next
...

Inspecting Variables and Memory

Standard gdb commands work at any point:

  • print <var>: Print variable value
  • print *<ptr>: Dereference pointer
  • x/<format> <address>: Examine memory
    • x/10xb <addr>: 10 bytes in hex
    • x/s <addr>: String at address
  • info locals: Show local variables
  • info args: Show function arguments

Source vs Assembly View

  • list: Show source code around current location
  • disassemble: Show assembly around current location
  • layout src: TUI source view
  • layout asm: TUI assembly view
  • set disassemble-next-line on: Show assembly with each step

Automation Script

Use scripts/crash_trace.py to automatically extract execution trace before crash.