C++ Debug & Audit Skill

Use this skill for debugging C++ issues and performing systematic safety audits.

Debug Priority

When debugging crashes or memory issues, check in this order:

1. Use-after-free / dangling references — sanitizers first (-fsanitize=address)
2. Buffer overflows — -fsanitize=undefined
3. Data races — -fsanitize=thread
4. Uninitialized reads — -fsanitize=memory (Clang)
5. Double-free — check RAII ownership
6. Stack overflow — check recursion depth, large stack allocations
7. ABI mismatch — check linking, ODR violations

Audit Checklist

For systematic safety audit:

• All raw pointers classified (owning vs non-owning)
• All resources wrapped in RAII
• No new/delete in application code
• No mutable global state without synchronization
• No detached threads
• Lock ordering documented
• Error handling strategy consistent per module
• No throwing from destructors
• Move semantics correct (no move-from-const)
• string_view/span lifetime verified
• No virtual calls in constructors/destructors

Tool Usage

# Address sanitizer
clang++ -fsanitize=address -g -O1 source.cpp

# Thread sanitizer
clang++ -fsanitize=thread -g -O1 source.cpp

# Undefined behavior sanitizer
clang++ -fsanitize=undefined -g -O1 source.cpp

# Static analysis
clang-tidy source.cpp --config-file=config/.clang-tidy -- -std=c++20

# Run with Valgrind (Linux)
valgrind --leak-check=full --track-origins=yes ./program

Output Format

Root Cause Analysis

What is the most likely cause? What evidence supports it?

Reproduction

Minimum steps to reproduce.

Fix

Precise fix with explanation of why it works.

Prevention

What rule or check would catch this class of bug in the future?