Cursor rule

1---
2paths:
3  - "**/*.cpp"
4  - "**/*.hpp"
5  - "**/*.cc"
6  - "**/*.hh"
7  - "**/*.cxx"
8  - "**/*.h"
9  - "**/CMakeLists.txt"
10---
11# C++ Patterns
12 
13> This file extends [common/patterns.md](../common/patterns.md) with C++ specific content.
14 
15## RAII (Resource Acquisition Is Initialization)
16 
17Tie resource lifetime to object lifetime:
18 
19```cpp
20class FileHandle {
21public:
22    explicit FileHandle(const std::string& path) : file_(std::fopen(path.c_str(), "r")) {}
23    ~FileHandle() { if (file_) std::fclose(file_); }
24    FileHandle(const FileHandle&) = delete;
25    FileHandle& operator=(const FileHandle&) = delete;
26private:
27    std::FILE* file_;
28};
29```
30 
31## Rule of Five/Zero
32 
33- **Rule of Zero**: Prefer classes that need no custom destructor, copy/move constructors, or assignments
34- **Rule of Five**: If you define any of destructor/copy-ctor/copy-assign/move-ctor/move-assign, define all five
35 
36## Value Semantics
37 
38- Pass small/trivial types by value
39- Pass large types by `const&`
40- Return by value (rely on RVO/NRVO)
41- Use move semantics for sink parameters
42 
43## Error Handling
44 
45- Use exceptions for exceptional conditions
46- Use `std::optional` for values that may not exist
47- Use `std::expected` (C++23) or result types for expected failures
48 
49## Reference
50 
51See skill: `cpp-coding-standards` for comprehensive C++ patterns and anti-patterns.
52