This issue tracks Clang/LLVM bugs that we have workarounds for.

We cite bugs as LLVM-<nnn> using the https://llvm.org/PR<nnn> redirector that maps old Bugzilla numbers to new GitHub numbers. I've listed the old citations here so we can easily search MSVC's STL.

Open

• LLVM-15544 Address Sanitizer doesn't call new_handler when allocation fails llvm/llvm-project#15916
• LLVM-23106 Division followed by modulo generates longer machine code than vice versa llvm/llvm-project#23480
• LLVM-35365 ASAN on Windows dies on exception re-throw llvm/llvm-project#34713
• LLVM-35450 Spurious -Wunused-lambda-capture in presence of "if constexpr" llvm/llvm-project#34798
• LLVM-37932 Division of uin64_t by constant on ARM32 should multiply by inverse llvm/llvm-project#37280
• LLVM-38217 Clang/LLVM optimizes division and modulo worse than MSVC, part 2 llvm/llvm-project#37565
• LLVM-41915 Implement CWG 1496 llvm/llvm-project#41260
• LLVM-44688 Bogus reference bindings incorrectly accepted llvm/llvm-project#44033
• LLVM-46207 tgmath.h broken when compiling C with clang-cl llvm/llvm-project#45552
• LLVM-46685 Implement __builtin_zero_non_value_bits which was recently added to MSVC for P0528R3 and P1123R0 llvm/llvm-project#46030
• LLVM-48220 clang-cl: ignore /Zc:preprocessor llvm/llvm-project#47564
• LLVM-48860 MSVC Compatibility: Implement intrinsics for P0466R5 - Layout-compatibility and Pointer-interconvertibility Traits llvm/llvm-project#48204
• C++ compiler should forbid throw move-only type llvm/llvm-project#53224
• [ASAN] [x86] Thrown exceptions corrupt stack near catch site llvm/llvm-project#54804
• explicitly noexcept destructor incorrectly not constexpr llvm/llvm-project#59854
• clang c++20: Associated constraints added to a default constructor are excessively checked llvm/llvm-project#60293
• [libc++][test] Should avoid preprocessor directives in macro argument lists llvm/llvm-project#73836
• [AArch64][Windows] Don't omit frame pointers in -Od llvm/llvm-project#74530
• [libc++] std::regex match_prev_avail implementation is regressed llvm/llvm-project#74838
• clang incorrectly considers top-level cv-qualifiers when determining the parameter mapping for subsumption llvm/llvm-project#75404
• clang reports about unuses captured this in lambda with -Wunused-lambda-capture llvm/llvm-project#81243
• [libc++][format] Formatting range with m range-type is incorrect llvm/llvm-project#90196
• LWG2584: <regex> ECMAScript IdentityEscape is ambiguous llvm/llvm-project#99976
• [libc++][test] Precondition violation in rand.dist.uni.real/param_ctor.pass.cpp llvm/llvm-project#100506
• P2590R2: Explicit lifetime management llvm/llvm-project#105234
• [Clang] Placement-new in constant evaluation can give indeterminate result llvm/llvm-project#117294
• [libc++][test] re.regex.construct/bad_backref.pass.cpp assumes non-standard extension to extended regular expressions llvm/llvm-project#122638
• [libc++][test] Make narrowing in nasty_char_traits::to_char_type more explicit llvm/llvm-project#138375
• Clang 20 i686-pc-windows-msvc regression, silent bad codegen for std::current_exception() llvm/llvm-project#158302
• [Clang] __builtin_common_type is overly permissive llvm/llvm-project#171438
• [libc++][test] facet.num.get.members/get_long.pass.cpp uses std::to_string() without including <string> llvm/llvm-project#182390
• [libc++][test] vector/trivial_relocation.pass.cpp uses implementation-specific attribute [[clang::trivial_abi]] llvm/llvm-project#182392
• [libc++][test] rand.dist.bern.negbin/eval.pass.cpp constructs with p == 1, which has undefined behavior llvm/llvm-project#182397
• [Clang] reference_constructs_from_temporary mishandles cv-qualified arrays llvm/llvm-project#198580
• [Clang] Clang incorrectly calculates constraints involving private members and multiple nested classes of the same name llvm/llvm-project#198716

Fixed in Clang 23

• [ASan][Windows] Fixing Windows shadow memory address for arm64 llvm/llvm-project#184902
• [Clang] Compiler regression affecting concept-constrained flat_map::at() llvm/llvm-project#198663