C++ Patterns

This file extends common/patterns.md with C++ specific content.

RAII (Resource Acquisition Is Initialization)

Tie resource lifetime to object lifetime:

class FileHandle {
public:
    explicit FileHandle(const std::string& path) : file_(std::fopen(path.c_str(), "r")) {}
    ~FileHandle() { if (file_) std::fclose(file_); }
    FileHandle(const FileHandle&) = delete;
    FileHandle& operator=(const FileHandle&) = delete;
private:
    std::FILE* file_;
};

Rule of Five/Zero

• Rule of Zero: Prefer classes that need no custom destructor, copy/move constructors, or assignments
• Rule of Five: If you define any of destructor/copy-ctor/copy-assign/move-ctor/move-assign, define all five

Value Semantics

• Pass small/trivial types by value
• Pass large types by const&
• Return by value (rely on RVO/NRVO)
• Use move semantics for sink parameters

Error Handling

• Use exceptions for exceptional conditions
• Use std::optional for values that may not exist
• Use std::expected (C++23) or result types for expected failures

Reference

See skill: cpp-coding-standards for comprehensive C++ patterns and anti-patterns.