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🟡 Changes recommended
The new guidance incorrectly rejects <utility> as the standard header for C++23’s std::unreachable.
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What changed in this PR
Expands Chapter 13’s undefined-behavior guidance through C++26 while preserving the C++20 baseline and leaving executable examples unchanged.
Changes:
- Corrects the explanation of guarded null-pointer access.
- Adds coverage of lifetime, concurrency, diagnostics, and newer language facilities.
- Numbers body sections for chapter-structure validation.
| File | Description |
|---|---|
01_low_level/13_ub/README.md |
Expands UB explanations and updates chapter organization. |
Review effort: Balanced
Comment on lines
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| ```cpp | ||
| #include <utility> // for other modern utilities | ||
| // #include <utility> is NOT the home of std::unreachable; | ||
| // include <utility> for std::to_underlying, <utility> notwithstanding. | ||
| // C++23: #include <utility> is not sufficient; use <utility> only for its own APIs. | ||
| ``` | ||
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| Do not use `std::unreachable` to handle untrusted input or an incomplete switch. Instead throw, return an error, or terminate deliberately according to the API. In C++23 its header is `<utility>`? No: use the documented `<utility>`/implementation reference for target library rather than guessing from legacy builtins. |
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Deep review of the UB demonstrations. Corrected the misleading claim that an optimizer may remove a correct preceding null guard. Added technical analysis of overflow, lifetime, aliasing, concurrency, atomic reclamation, constant evaluation, C++23 unreachable, and C++26 checked arithmetic, contracts and uninitialized values. Numbered the chapter for the structure checker introduced in PR #15; C++20 baseline unchanged. README-only.