This issue tracks /clr compiler bugs that we need fixes for.

/clr /std:c++20 was first supported (excluding modules) in VS 2022 17.6.

Legend

• 📦 Not reduced, preprocessed repro
• 😸 Semi-reduced, pruned unnecessary test code
• 💚 Fully reduced, library-free repro

Product Code Workarounds

• 💚 VSO-1153256 Issue: [[msvc::noop_dtor]] doesn't seem to work for /clr
• 😸 VSO-1663104 /clr rejects the __ceilf/__floorf intrinsics with error LNK2020/LNK2001 instead of accepting or falling back to native codegen
• 😸 VSO-1664341 /clr C++20 System.NullReferenceException when calling ranges algorithms with PMD projections
• 📦 VSO-1665606 /clr C++20 backend ICE with counted_iterator's _Same_sequence
• 😸 VSO-2457624 /clr /std:c++20 silent bad codegen with the __fastfail intrinsic

Test Code Workarounds

• 😸 VSO-1659383 /clr atomic and thread emit error C2711 "this function cannot be compiled as managed" instead of falling back to native codegen
• 😸 VSO-1659496 /clr emits bogus error C2079 "uses undefined struct 'Incomplete'" despite std::variant's ADL defenses
• 😸 VSO-1659511 /clr runtime hang when calling std::async in a global variable's constructor
• 📦 VSO-1664382 /clr C++20 emits bogus error C2127 "illegal initialization of 'constinit' entity with a non-constant expression"
• 💚 VSO-1665481 /clr C++20 silent bad codegen for complex<float> division
• 📦 VSO-1665670 /clr C++20 incorrectly reports input_iterator etc. concepts as being true for 'bad' iterators
• 📦 VSO-1665674 /clr C++20 has incorrect results for various ranges concepts in P0896R4_ranges_iterator_machinery
• 😸 VSO-1666161 /clr C++20 silent bad codegen for bit_cast<float>(nan_uint)
• 💚 VSO-1666178 /clr C++20 x64 /O2 backend assertion SY_ISUSERVAR(sym) || SY_ISARGUMENT(sym)
• 💚 VSO-1846195 /clr alignas emits fatal error C1193: an error expected in yyaction.cpp(2971) not reached
• 😸 VSO-1946395 /clr /std:c++20 /Od backend ICE for parallel std::find_end

No Workarounds

• 💚 VSO-1459687 DevCom-1632617 C++/CLI struct/class doesn't use MarshalCopy
  • Reported in Iterator debugging asserts in mixed managed/native code #139.
• 💚 VSO-2231268 /clr /std:c++20 rejects sneaky technique to access private data members
  • Perma-workaround in <chrono>: Add comments for compiler bug workarounds #4920.
• 💚 VSO-2279389 /clr C++20 can't handle struct MoveOnlyFunctor defined in a function template, emitting fatal error C1193: an error expected in yyaction.cpp(2899) not reached
  • Perma-workaround in <future>: Make packaged_task accept move-only functors #4946.
• 💚 VSO-2616030 /clr /std:c++20 alignas emits bogus error C3645: 'main::<lambda_1>::<lambda_invoker_clrcall>': __clrcall cannot be used on functions compiled to native code
  • Perma-workaround in <__msvc_threads_core.hpp>: Use aligned byte arrays as aligned buffers #5811.

Fixed

• VSO-1078742 DevCom-939490 Calling a pointer to member function at constexpr time in /clr triggers internal compiler error
• VSO-1663233 /clr C++20 rejects <coroutine> with error C3861 "'__builtin_coro_done': identifier not found" instead of falling back to native codegen
• VSO-1680392 Assertion failure: pSTI->length == strlen(pSTI->szName) + 1 under /clr
• VSO-1595465 /clr /std:c++17 ICE with int = 0 SFINAE
• VSO-1663257 /clr C++20 rejects P0428R2 Familiar template syntax for generic lambdas
• VSO-1663301 /clr C++20 emits bogus error C2131 'expression did not evaluate to a constant' when a lambda tests a constexpr variable defined outside
• VSO-1665663 /clr C++20 source_location has incorrect column information within a lambda
• VSO-1664463 /clr C++20 alignas emits error C3821 'managed type or function cannot be used in an unmanaged function' instead of falling back to native codegen
• VSO-1659408 /clr alignas emits error C2711 "this function cannot be compiled as managed" instead of falling back to native codegen
• VSO-1666180 /clr C++20 x64 System.AccessViolationException with views::iota and views::transform
  • Duplicate: VSO-1659489 /clr System.AccessViolationException with parallel std::mismatch
  • Duplicate: VSO-1867037 /clr C++20 System.AccessViolationException with ranges uninitialized algorithms
• VSO-1665654 /clr C++20 x86 System.AccessViolationException with atomic<shared_ptr>
• VSO-1659695 /clr x86 runtime assertions/crashes with parallel algorithms
• VSO-1658184 /clr silent bad codegen with std::_Signed128 multiplication
• VSO-1881472 /clr C++20 x86 System.AccessViolationException with atomic<with_padding_bits<8>>
• VSO-1664293 /clr C++20 chk assertion failed: rhs.is_lvalue() in constexpr.cpp
• VSO-2417635 /clr C++20 chk assertion failed: rhs.is_lvalue() in constexpr.cpp, again