Memory Safety Check Skill

Validate Mojo ownership and borrowing rules.

When to Use

• Reviewing code for memory safety
• Debugging memory or segfault issues
• Before merging code
• Performance testing reveals corruption

Quick Reference

# Owned parameter - takes ownership
fn consume(var data: Tensor):
    process(data)  # data moved here

# Borrowed parameter - read-only reference
fn read_only(data: Tensor):
    let value = data[0]  # OK: read-only

# Mutable reference - in-place modification
fn modify(mut data: Tensor):
    data[0] = 42  # Mutate in caller's variable

Workflow

1. Trace ownership - Which function owns each value
2. Check borrows - Are references short-lived
3. Verify moves - Use ^ operator for ownership transfer
4. Test lifetimes - Compile and run with memory checks
5. Debug issues - Identify use-after-move or dangling refs

Mojo-Specific Notes

• Use ^ operator ONLY when transferring ownership
• mut self for mutating methods (NOT out self)
• out self ONLY for constructors (__init__)
• List/Dict/String are non-copyable - must use ^ when returning

Error Handling

References

• .claude/shared/mojo-anti-patterns.md - Ownership violations section
• .claude/shared/mojo-guidelines.md - Parameter conventions table