Choose appropriate string types

Select the most efficient string type based on ownership and lifetime requirements to optimize memory usage and prevent safety issues. Use StringRef for parameters and when you don’t need to own the string data, std::string when you need ownership and persistence, and avoid storing Twine objects as member variables.

Key guidelines:

• Use StringRef for function parameters when you only need to read the string
• Use std::string for member variables when you need to own and persist the data
• Never store Twine as a member variable - it doesn’t own its underlying data and can cause memory violations
• Consider whether you’re making unnecessary copies of constant strings

Example from the discussions:

// Bad: Unnecessary string copy for constant data
class InvalidRSMetadataFormat {
  std::string ElementName;  // If always called with constants
};

// Good: Use StringRef when appropriate
class InvalidRSMetadataFormat {
  StringRef ElementName;  // For constant strings
};

// Bad: Dangerous storage of Twine
class GenericRSMetadataError {
  Twine Message;  // Can cause memory violations
};

// Good: Own the string data when needed
class GenericRSMetadataError {
  std::string Message;  // Safe ownership
};

This optimization reduces memory allocations, prevents unnecessary copying, and avoids potential memory safety issues while maintaining code correctness.