Noexcept? Enabling Testing of Contract Checks Pablo Halpern and Timur Doumler This work by Pablo Halpern & Timur Doumler is licensed under a Creative Commons Attribution 4.0 International License Doumler, 2023 (CC BY 4.0) 2 Today’s talkGoals −What We Hope to Teach You • How the noexcept specifier and noexcept operator work and what they are for • The importance of writing contracts and checking checking them at run time • How to unit test contract-checking annotations (CCAs) • How noexcept interacts with unit testing of CCAs. We will go over everything twice! 4-Oct-23 Pablo Halpern and Timur Doumler

assignment 7 constexpr extents () noexcept = default; 8 constexpr extents(const extents &) noexcept = default; 9 constexpr extents& operator =( const extents &) noexcept = default; 10 11 template &) noexcept; 13 template 14 constexpr extents(IndexType ...) noexcept; 15 template 16 constexpr extents(const array &) noexcept; 17 template 18 constexpr extents& operator =( const extents < OtherExtents ... >&) noexcept; 19 20 // [mdspan.extents.obs], Observers

Capacity > class FixedVector final { public: // ... // ... }; Type begin() noexcept; * Type end() noexcept; *Const Correctness 45 Task: What is wrong with the declaration of the begin() and Capacity > class FixedVector final { public: // ... // ... }; Type begin() noexcept; * Type end() noexcept; * const&Const Correctness 46 Task: What is wrong with the declaration of the begin() class FixedVector final { public: // ... // ... }; Type begin() const noexcept; * Type end() const noexcept; *Const Correctness 47 Task: What is wrong with the declaration of the begin()

hazard_pointer_domain { public: hazard_pointer_domain() noexcept; explicit hazard_pointer_domain( pmr::polymorphic_allocator poly_alloc) noexcept; hazard_pointer_domain(const hazard_pointer_domain&) hazard_pointer_default_domain() noexcept; // For synchronous reclamation void hazard_pointer_clean_up( hazard_pointer_domain& domain = hazard_pointer_default_domain()) noexcept; 20 © 2021. 21 Hazard Pointers hazard_pointer_default_domain()) noexcept; void retire(hazard_pointer_domain& domain) noexcept; }; 21 © 2021. 22 Hazard Pointers TS2 Interface class hazard_pointer { public: hazard_pointer() noexcept; // Empty h

2020 #include std::move template constexpr remove_reference_t&& move(T&& t) noexcept { return static_cast&&>(t); } Definition52 David Olsen — Back to Basics: 2020 #include std::move template constexpr remove_reference_t&& move(T&& t) noexcept { return static_cast&&>(t); } Definition constexpr function taking one 2020 #include std::move template constexpr remove_reference_t&& move(T&& t) noexcept { return static_cast&&>(t); } Definition Returns an rvalue reference54

std::ptrdiff_t UtfUtils::BasicConvert(char8_t const* pSrc, char8_t const* pSrcEnd, char32_t* pDst) noexcept { char32_t* pDstOrig = pDst; char32_t cdpt; while (pSrc < pSrcEnd) { if (Advance(pSrc, pSrcEnd KEWB_FORCE_INLINE int32_t UtfUtils::Advance(char8_t const*& pSrc, char8_t const* pSrcEnd, char32_t& cdpt) noexcept { FirstUnitInfo info; //- The descriptor for the first code unit char32_t unit; //- std::ptrdiff_t UtfUtils::BasicConvert(char8_t const* pSrc, char8_t const* pSrcEnd, char32_t* pDst) noexcept { char32_t* pDstOrig = pDst; char32_t cdpt; while (pSrc < pSrcEnd) { if (Advance(pSrc, pSrcEnd

my::contract_violation_exception(violation); } User-defined contract-violation handler Lakos Rule = Do not put noexcept on a function with preconditions, even if it never throws when called correctly! C++ Standard std::source_location location() const noexcept; const char* comment() const noexcept; detection_mode detection_mode() const noexcept; evaluation_semantic semantic() const noexcept; assertion_kind assertion_kind kind() const noexcept; }; void invoke_default_contract_violation_handler(const contract_violation&); } Standard Library API105 Copyright (c) Timur Doumler | @timur_audio | https://timur

template T atomic_fetch_max(atomic*, typename atomic::value_type) noexcept; template T atomic_fetch_max_explicit(atomic*, typename atomic::value_type, memory_order) noexcept; // Similar for atomic_fetch_min // Member functions on atomic }Performance Considerations & Benchmark float fetch_min(float, memory_order = memory_order::seq_cst) noexcept; float fetch_max(float, memory_order = memory_order::seq_cst) noexcept; Semantics: ● Unspecified behavior with NaNs. ● Treats -0

Ignores any trailing non-integer part 10 Integer Parsing optional real_atoi(const char* str) noexcept { const auto result = std::atoi(str); if (result) { return result; } while (*str && Callers can easily skip whitespace if they want: std::find_if_not(first, last, [](const char c) noexcept { const unsigned char u(c); return std::isspace(u); }); What if they consider leading whitespace bad_decimal }; std::error_code make_error_code(error e) noexcept { static const struct : std::error_category { virtual const char* name() const noexcept override { return "Decimal Parser"; }

with warning flags [[clang::nonallocating]] -Wfunction-effects -Wperf-constraint-implies-noexcept[[clang::nonblocking]] void dispatch() [[clang::nonblocking]] { m.lock(); } warning: 'nonblocking' [[clang::nonallocating]] implies noexcept requireswarning: 'nonblocking' function must not allocate or deallocate memory [-Wfunction-effects] 4 | float* ptr = new float; void dispatch() noexcept [[clang::nonblocking]] [[clang::nonallocating]] implies noexcept requireswarning: 'nonallocating' function should be declared noexcept 3 | void foo() -Wperf-constraint-implies-noexcept void foo() [[clang::nonallocating]];