Code Review

HPCC Platform Code Review Guidelines

Review Philosophy

• The goal is to catch bugs, design problems, security issues, and readability concerns.
• Consider interactions between components, e.g. Dali, Thor, and Roxie components.

Critical Quality Checks & Checklist

1. Memory Management

• Owned<> vs Linked<>: Owned<X> takes ownership of a new/returned pointer; Linked<X> shares ownership. Verify proper use.
• Check for memory/resource leaks in general. Are exceptions properly handled so resources are released?
• queryFoo() returns are NOT linked — caller must Link() if retaining beyond guaranteed lifetime.
• getFoo() returns ARE linked — assign to Owned<> or return directly.
• Are CInterface-derived objects properly release-counted?

2. Thread Safety

• Look for race conditions, proper locking, and synchronization issues, especially in server components.
• Are shared variables protected by critical sections or atomics? Watch for TOCTOU (time-of-check-time-of-use).
• Check for potential deadlocks (lock ordering).
• Are CriticalBlock, ReadLockBlock, WriteLockBlock scoped correctly?

3. Code Style (Essential Rules)

• Adherence to coding standards in devdoc/StyleGuide.md.
• Braces: Allman style — { and } on their own line. Single-line blocks may omit braces unless nested.
• Naming: CamelCase for classes, camelCase for variables/functions/methods.
• No trailing whitespace.
• Prefer constexpr over macros. Avoid default parameters (use method overloading instead).
• Format specifiers: %u for unsigned, %d for signed.

4. Error Handling & Correctness

• Consistent error reporting and logging throughout the codebase.
• Edge cases: empty inputs, null pointers, integer overflow, off-by-one.
• Are exceptions caught at the right level? Do they properly release resources?

5. Security & API Compatibility

• Validate input sanitization, authentication, and authorization mechanisms.
• Ensure changes don't break existing client interfaces or backward compatibility.
• Are public interface changes minimized and documented?
• SQL/command injection vectors?

6. Efficiency

• Consider effects on query execution and distributed data throughput.
• Unnecessary copies of large objects?
• String operations in hot paths (prefer StringBuffer over repeated std::string concatenation)?

7. Component-Specific Concerns

• Dali: Distributed metadata — watch for consistency, replication, and transaction issues.
• Thor: Batch processing — watch for data partitioning, memory limits, and spill-to-disk handling.
• Roxie: Real-time queries — watch for latency, caching, and query lifecycle management.
• ESP: Web services — watch for authentication, input validation, and CORS/CSRF.
• ECL compiler: Language changes — verify backward compatibility with existing ECL code.

Review Questions to Consider

• Are there any efficiency concerns or performance bottlenecks?
• Is the code thread-safe and properly synchronized?
• Could the code be refactored to improve maintainability and reuse?
• Are there any memory or resource leaks?
• Does this change maintain backward compatibility?
• Are error conditions properly handled and logged?
• Is the change properly tested with appropriate test coverage?