cpp.mdc

---
description: C++ class layout, coding conventions, and best practices
globs: "**/*.{cpp,hpp,h,cc,cxx}"
alwaysApply: false
---

# C++ Coding Conventions

> Based on [Vinnie Falco's](https://github.com/vinniefalco) C++ rules from [cppalliance/coro-io-context](https://github.com/cppalliance/coro-io-context)

## Class Layout

- Private data members first
- Public interface last
- Destructor comes first in the public section
- Use `struct` if all members are public, otherwise use `class`
- Little to no ASCII-art dividers

## Encapsulation

- Never break encapsulation without explicit instruction
- Prefer composition over inheritance where appropriate

## Error Handling

- Don't call `make_error_code` directly unless necessary
- Idiomatic `boost::system::error_code` check is `ec.failed()`, not `ec` or `!!ec`
- For `std::error_code`, use `if (ec)` or `ec.value() != 0`

## Min/Max Protection

- Always protect `min`/`max` with parentheses: `(std::min)(a, b)`
- Include `<algorithm>` sparingly - it's costly
- Don't include `<algorithm>` just for `min`/`max`

## Testing

- Always update the tests after changing code
- Write unit tests for public headers in corresponding `.cpp` files
- Test edge cases and error conditions

## Example Class Layout

```cpp
class connection
{
    // Private data members first
    socket socket_;
    buffer buffer_;
    bool connected_ = false;

public:
    // Destructor first
    ~connection();

    // Constructors
    connection();
    connection(connection&&) noexcept;
    connection& operator=(connection&&) noexcept;

    // Deleted operations
    connection(connection const&) = delete;
    connection& operator=(connection const&) = delete;

    // Public interface
    void connect(endpoint const& ep);
    void disconnect();
    bool is_connected() const noexcept;
};
```