# Correctness & Modern Idioms

Docs: cppreference language/library pages; C++ Core Guidelines.

## Errors & exceptions

- Errors aren't silently ignored (unchecked return codes, empty `catch (...)`).
- Mark functions whose result must be used `[[nodiscard]]`.
- Exception safety: on throw, no leaks and objects stay valid (RAII gives this
  for free).
- Destructors and move operations are `noexcept`; no throwing from destructors.
- Catch exceptions by const reference (`catch (std::exception const& e)`).
- Consider `std::optional` / `std::expected` (C++23) for expected failures, per
  project style.

## Types & integers

- Fixed-width integers: use the project's aliases (`u32`, `i64`, ...) instead of
  `std::uint32_t` etc., e.g. for sizes in protocols, files, and hardware.
- Signed/unsigned comparison and mixing (`int` vs `size_t`); use `std::cmp_less`
  etc. (C++20) or `std::ssize`.
- Narrowing conversions are explicit and checked; prefer `{}` initialization to
  catch them.
- No implicit conversions via single-arg constructors; mark them `explicit`.
- `enum class` over plain `enum`.

## API & classes

- `const` correctness: methods, references, and parameters.
- Pass cheap types by value, large read-only by `const&`, sinks by value +
  `std::move`.
- `override` on virtual overrides; `final` where intended.
- No object slicing (passing derived by value as base).
- Header hygiene: include what you use, no `using namespace` in headers.

## Modern idioms

- Prefer standard algorithms and range-for over hand-rolled loops.
- `constexpr` for compile-time constants instead of macros.
- `std::string_view` / `std::span` for non-owning parameters (watch lifetimes).
- New logic has tests; edge cases (empty, max, error path) are covered.