57 lines
2.8 KiB
Markdown
57 lines
2.8 KiB
Markdown
# GitHub Copilot Repository Instructions: C++23 Modernization
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## Context
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- Language: C++
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- Target standard: C++23
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- Goal: modernize legacy C++11/14/17 code safely and incrementally
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## Primary Rule
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Preserve existing behavior unless functional changes are explicitly requested.
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## Balanced Modernization Policy
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- Prefer modern C++23 constructs when they clearly improve safety, readability, or maintainability.
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- Keep refactors focused and reviewable; avoid broad rewrites unless requested.
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- Prefer standard library solutions over custom or legacy patterns.
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- Respect toolchain limitations, ABI-sensitive interfaces, and repository-local style.
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## Preferred Modernizations
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- Use `auto` where the type is obvious from the initializer; avoid it when it hides important type information.
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- Prefer structured bindings over `std::tie` or manual pair/tuple access when clearer.
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- Replace raw owning pointers and manual `delete` with RAII, usually `std::unique_ptr`.
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- Use `std::make_unique` and `std::make_shared`; prefer `std::shared_ptr` only for real shared ownership.
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- Use `std::string_view` for read-only string parameters only when lifetime safety is clear.
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- Prefer `std::span` for non-owning contiguous ranges.
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- Use `std::mdspan` only when multidimensional access is central and the change improves clarity or safety.
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- Prefer `.contains()` over `find(...) != end()` where available and clearer.
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- Prefer standard algorithms and ranges over manual loops when readability improves.
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- Use `[[nodiscard]]` where ignoring the result is likely a bug.
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- Prefer early returns over deeply nested control flow.
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- Use `std::optional` monadic operations (`and_then`, `transform`, `or_else`) when they make the code simpler.
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- Prefer `constexpr`, `if constexpr`, concepts, and `requires` over legacy `std::enable_if` / SFINAE where practical.
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- Add `noexcept`, `override`, `final`, `= default`, and `= delete` where correct and useful.
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- Prefer `enum class` over unscoped enums where practical.
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- Prefer `std::print` / `std::println` for console output when supported by the project toolchain.
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- Prefer typed `std::chrono` durations and `std::jthread` where appropriate.
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## Avoid
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- Do not modernize mechanically if readability becomes worse.
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- Do not introduce unsupported C++23 features.
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- Do not introduce dangling references, dangling `std::string_view`, or unclear ownership.
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- Do not silently change ABI, object lifetime, exception behavior, or performance characteristics.
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- Do not rewrite unrelated code.
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## Expected Copilot Behavior
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When making migration suggestions:
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- produce small, focused updates
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- explain non-trivial changes briefly
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- call out risky refactors explicitly
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- note compatibility or toolchain caveats
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- leave optional follow-up improvements separate
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## Preferred Output
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Provide:
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- updated code
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- short rationale
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- compatibility/toolchain caveats
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- optional next modernization steps
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