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Standard Library Header Units and Modules - tracking issue

Open StephanTLavavej opened this issue 4 years ago • 1 comments

:scroll: Documentation

:construction: Status

  • Standard Library Header Units are ready for production use, for MSVC only.
    • Shipped in VS 2019 16.11.
  • Standard Library Modules are ready for production use, for MSVC only.
    • Shipped in VS 2022 17.5: #3108
  • The C++23 named modules std and std.compat are available when compiling in C++20 mode.
    • Shipped in VS 2022 17.8: #3977
    • This extension is supported by the major Standard Library implementations via an informal agreement between implementers.
  • #include <meow> can coexist with import std; in the same translation unit, in that order.
    • Shipped in VS 2022 17.10: #4154
    • The other order, import std; before #include <meow>, will still cause compiler errors. We're working on a long-term solution.

We've reported the following compiler bugs; this issue is for tracking the status of these compiler bugs and removing workarounds/adding test coverage as compiler fixes are released. As you can see below, a ton of compiler bugs have been fixed. If you're using header units or named modules, I strongly recommend using the latest version of VS 2022.

As /clr C++20 support is a work in progress, we are not yet testing Standard Library Header Units or Modules under /clr.

:x: Clang

  • Clang currently lists C++20 modules as not yet fully implemented: https://clang.llvm.org/cxx_status.html#cxx20
  • I've heard from users that Clang 19 works with MSVC's Standard Library Modules but I haven't had a chance to test this yet.

:bug: EDG (IntelliSense Front-End)

  • EDG is currently investigating test failures. STL test coverage is not yet enabled. See #1621.

:lady_beetle: Active, C1XX (MSVC Front-End)

  • #3661
  • DevCom-1256361 VSO-1248260 "[C++][Modules][GMF] Named module leaks names from GMF"
    • This will cause the std module to export too much stuff.
  • VSO-1953157 "Modules: MSVC should emit an error when an exported declaration follows a non-exported declaration"
  • DevCom-10729775 VSO-2225134 "Standard Library Modules: Random number machinery emits bogus error C2512: 'std::_Unsigned128': no appropriate default constructor available"
    • Originally #4899
  • VSO-2226569 "Standard Library Modules: generate_canonical causes C1XX ICE: find_pending_comparison_function_for_definition(function) == std::end(pending_comparison_functions_for_definition)"
  • VSO-2227713 "Modules: Exported function templates can't use std::cout properly"
  • #5203
    • Need to analyze.
  • DevCom-10736790 VSO-2238628 "Reference NTTPs broken in modules (ICE)"
    • Reported to us as #5254

:hammer_and_wrench: Upcoming Improvements (C1XX)

  • Fixed 2025-09-08: VSO-1236041 "Standard Library Header Units: bogus error LNK2019: unresolved external symbol pair(piecewise_construct_t, tuple, tuple)"

:grey_question: Possible Improvements (C1XX/MSBuild)

  • VSO-1330581 "Throughput for Standard Library Header Units"
  • VSO-1469758 "Standard Library Header Units: Possible IFC size reductions?"
  • VSO-1568412 "Standard Library Modules: Enhanced diagnostics for needing import std.compat;, std::printf, or std::cout"
  • VSO-1621267 "Standard Library Modules: Enhanced diagnostics for missing macros"
  • VSO-1922468 "Standard Library Modules: Helpful diagnostic when import std; is seen, but std.ifc/std.obj need to be built"
  • VSO-1922469 "Support C++20 builds of import std; and import std.compat;"
  • VSO-1987212 "[C++ Modules DT perf] STL modules are always scanned in designtime regardless of their usage in code"

:adhesive_bandage: Permanent Workarounds

  • VSO-1308657 "Standard Library Header Units: std::projected::operator*() error LNK2019: unresolved external symbol"
    • Perma-workaround: provide a definition that calls abort().

:heart_eyes_cat: Fixed, Workaround Removed

  • Fixed in 16.8:
    • DevCom-1160043 VSO-1168062 "Standard Library Header Units: Bogus error C2131 when using compare functions at compile-time"
    • DevCom-1160145 VSO-1180193 "Standard Library Header Units: error LNK2019 'unresolved external symbol' when a function is declared in one header and defined in another"
  • Fixed in 16.9:
    • DevCom-1159869 VSO-1180127 "Standard Library Header Units: Bogus warning C4373 about virtual function overriding"
    • DevCom-1159995 VSO-1180128 "Standard Library Header Units: UDLs don't compile, depending on the order of imports"
    • DevCom-1160260 VSO-1180207 "Standard Library Header Units: Bogus error C2752: 'std::pointer_traits<_Voidptr>': more than one partial specialization matches the template argument list"
    • DevCom-1161187 VSO-1181303 "Standard Library Header Units: Bogus error C2248 'cannot access private member'"
    • DevCom-1162644 VSO-1181305 "Standard Library Header Units: __pragma(warning(disable : 4996)) doesn't take effect"
    • DevCom-1224512 VSO-1236022 "Standard Library Header Units: Bogus error C2027: use of undefined type 'std::char_traits'"
    • VSO-1236034 "Standard Library Header Units: bogus error LNK2005: std::_Yarn<char>::operator=(char const *) already defined"
    • VSO-1236047 "Standard Library Header Units: std::optional, c1xx!FindConversionFunctions() assertion failed: PF_ISSET(ParsingClassTemplateDefn)"
    • VSO-1237804 "Standard Library Header Units: std::variant, c1xx!Module::InterfaceReader::materialize_function() assertion failed"
    • VSO-1237145 "Standard Library Header Units: bogus error C7599: 'std::ranges::operator ==': a trailing requires clause is only allowed on a templated function"
  • Fixed and implemented in 16.10:
    • VSO-1271718 "Standard Library Header Units ICE with C++20 chrono"
    • VSO-1180134 DevCom-1160041 "Standard Library Header Units: deprecated attributes aren't imported"
    • VSO-1273005 "[Modules] c1xx does not fully resolve templates imported from IFC in the context of trailing requirements"
    • VSO-1284279 "Standard Library Header Units: memory_resource ICE: Mapping already has an entry defined at this slot"
    • VSO-1287222 "[modules] transitive header unit imports do not import macros"
    • VSO-1287925 "/headerUnit:angle ICEs"
    • VSO-1307828 "Standard Library Header Units: ICE with queue's friend bool operator=="
    • VSO-1309454 "Standard Library Header Units: CTAD fails when deduction guides are duplicated across header units"
    • VSO-1314139 "Cannot build header units for STL headers with 'Translate Includes to Imports'"
    • VSO-1232145 "EDG ICEs when consuming Standard Library Header Units"
    • Implemented /headerUnit:angle vector=vector.ifc
    • Implemented support for header-units.json via /sourceDependencies:directives and /translateInclude
    • Implemented /exportHeader /headerName:angle algorithm type_traits vector
  • Fixed in 16.11:
    • VSO-1330589 "Standard Library Header Units: Bogus error C2131 with _Nontrivial_dummy_type's constructor"
    • VSO-1330591 "Standard Library Header Units: Bogus error C2676 with type_info's equality operator"
    • DevCom-1440183 VSO-1337327 "Constexpr Function Involving String Does Not Compile When Consuming Modules"
  • Fixed in 17.0:
    • GH-1919 VSO-1329224 "Bogus error C2668 when importing <format> as a header unit"
    • VSO-1329976 "Standard Library Header Units: _CrtGetAllocHook emits warning C5106: macro redefined with different parameter names"
  • Fixed in 17.1:
    • DevCom-1511903 VSO-1384883 "Standard Library Header Units: Bogus error C2440 when convertible_to constrains a constructor"
    • VSO-1409853 "Standard Library Header Units: <ranges> compiler assertion: previous_element == tokenInputStack.TopOfStack(), aliastemplates.cpp 1010"
    • VSO-1433873 "Standard Library Header Units: Adding template <int = 0> to vformat() emits warnings C4265 and C4365"
  • Fixed in 17.2:
    • VSO-1464637 "Standard Library Header Units: #pragma warning doesn't always suppress warnings in templates"
    • VSO-1466711 "/scanDependencies generates incorrect "logical-name" in JSON output"
    • VSO-1471374 "Standard Library Header Units: Deduplication emits fatal error C1116: unrecoverable error importing module, with <concepts>"
    • VSO-1471376 "Standard Library Header Units: Confusing diagnostic for fatal error C1116: unrecoverable error importing module ''"
    • VSO-1471382 "Standard Library Header Units: Deduplication emits error C2672: 'count_if': no matching overloaded function found"
  • Fixed in 17.3:
    • VSO-1496074 "Standard Library Modules: C++20 chrono::days emits bogus error C2131"
    • VSO-1496084 "Standard Library Header Units: Splitting <chrono> emits fatal error C1116: unrecoverable error importing header unit '<chrono>'"
    • VSO-1496493 "Standard Library Modules: Implementing std.ixx emits fatal error C1011: cannot locate standard module interface"
    • VSO-1497379 "Standard Library Modules: extern "C" function declarations taking extern "C" types emit bogus error LNK2019: unresolved external symbol"
    • VSO-1504872 "Standard Library Modules: extern "C" function mentioning entity with module linkage is being marked with module linkage"
    • VSO-1526632 "Standard Library Header Units: Hidden friend operators cause ICE in Module::InterfaceReader::materialize_function<Module::helpers::MemberBuilder>()"
    • VSO-1513874 "Changing construct_at SFINAE causes Modules bogus error C2660: 'operator new': function does not take 3 arguments"
    • VSO-1533852 "Standard Library Modules: The Mega-Bug"
      • <codecvt>: fatal error C1001: Internal compiler error.
      • <any>: error C2679: binary '!=': no operator found which takes a right-hand operand of type 'const type_info' (or there is no acceptable conversion)
      • <memory>: error C2679: binary '==': no operator found which takes a right-hand operand of type 'const type_info' (or there is no acceptable conversion)
      • <functional>: error C2027: use of undefined type 'type_info'
      • <typeinfo>: error C2872: 'type_info': ambiguous symbol
      • <typeindex>: error C2440: 'initializing': cannot convert from 'initializer list' to 'std::type_index'
      • <regex>: Assertion failed: Nerrors > 0, file D:\msvc\src\vctools\Compiler\CxxFE\sl\p1\c\trees.c
    • VSO-1540220 "Standard Library Modules: /d1ifcInlineFunctions asserts (bits::rep(typeEncoding.basicEncoding_) & 0x0000000F) != 0 for printf(_Format, ...)"
    • VSO-1543660 "Standard Library Header Units: <expected> ICEs with Assertion failed: IsInClassDefn()"
    • VSO-1541639 "Standard Library Modules: error C3083: '_Iterator_base12': the symbol to the left of a '::' must be a type"
    • VSO-1509503 "Standard Library Header Units: Deduplication interferes with ADL for global operator&"
  • Fixed in 17.4:
    • VSO-1538668 "Compiler does not bind names inside of lambda nested in function template with parameter pack"
    • https://github.com/StephanTLavavej/STL/issues/13 VSO-1581022 "Standard Library Modules: inline constexpr variables for ranges::views emit error LNK2019: unresolved external symbol"
    • VSO-1567850 "Standard Library Modules: UCRT headers emit error C2294: cannot export symbol 'memcpy_s' because it has internal linkage"
    • VSO-1538666 "Compiler does not bind NSDMIs inside class templates"
    • VSO-1522454 "Standard Library Modules: Unresolved external symbol when extern "C++" is directly applied to a class with a static member function"
    • https://github.com/StephanTLavavej/STL/issues/17 VSO-1582910 "Standard Library Modules: ICE with std::views::join_with"
    • https://github.com/StephanTLavavej/STL/issues/18 VSO-1582916 "Standard Library Modules: ICE when class in named module inherits from variant with inheriting constructors"
    • VSO-1579484 "Standard Library Header Units: charconv refactoring + topo sort = error LNK2019: unresolved external symbol"
    • VSO-1593115 "Standard Library Modules: ICE with chunk_view of input iterators"
  • Fixed in 17.5:
    • VSO-1611408 "Standard Library Modules: Compiler assertion failed: inserted, file template.cpp, line 10275"
    • VSO-1611411 "Standard Library Modules: Compiler assertion failed: IsInClassDefn() && (region->owner == SU_TAG), file reader.cpp, line 2592"
    • #3112 DevCom-10154236 "<fstream>: Importing as a header unit leads to error C2079: undefined class 'std::basic_ofstream<char,std::char_traits<char>>'"
    • VSO-1592399 "Standard Library Modules: destroy_at() emits bogus error C2131: expression did not evaluate to a constant"
    • VSO-1592420 "Standard Library Modules: iota_view emits bogus error C7608: atomic constraint should be a constant expression"
    • VSO-1593015 "Standard Library Modules: constexpr vector::resize() ICE"
  • Fixed in 17.6:
    • https://github.com/StephanTLavavej/STL/issues/23 VSO-1584629 "Standard Library Modules: Usage of ranges::iterator_t causes ICE"
    • #3287 VSO-1706387 "<atomic>: Building a header unit with /ZI emits warning C5260"
    • VSO-1692469 "Standard library header units: deduplication causes ICE when combined with variable template specialization"
    • VSO-1592409 "Standard Library Modules: source_location::column() misbehaves in user headers"
    • #3330 DevCom-10247495 VSO-1714748 "MSVC forces us to export some internal enumeration functions for working with C++ modules"
    • #3333 VSO-1715231 "Standard Library Modules: Bogus error C2504: 'std::filesystem::_Dir_enum_impl': base class undefined"
    • DevCom-10241527 VSO-1711320 "VS 2022 17.5.0 Preview 2 import header unit charconv gives wrong result"
    • VSO-1592407 "Standard Library Modules: using namespace std::chrono; for UDLs emits bogus error C3688: invalid literal suffix"
    • VSO-1705654 "Standard Library Modules: /analyze ICE"
    • VSO-1593163 "Standard Library Modules: osyncstream move assignment emits bogus error C3083: 'basic_ostream<char,std::char_traits<char> >': the symbol to the left of a '::' must be a type"
    • VSO-1592329 "Standard Library Modules: Parallel sort() emits bogus error C2065: '_Atomic_counter_t': undeclared identifier"
    • https://github.com/StephanTLavavej/STL/issues/14 VSO-1582358 "Standard Library Modules: chrono formatting emits bogus error C3861: '_Fill_tm': identifier not found"
    • https://github.com/StephanTLavavej/STL/issues/15 VSO-1582381 "Standard Library Modules: Bogus warning C4702: unreachable code"
    • VSO-1720644 "Standard Library Modules: Scanning dependencies emits bogus warning C5244: '#include <meow>' in the purview of module 'std' appears erroneous"
    • VSO-1735035 "Standard Library Modules: ICE with P2165R4's tuple changes"
    • DevCom-10097021 VSO-1581774 "C++ STL header <format> causes C4296 warning that need to be suppressed every time" (with header units)
    • VSO-1752496 "Standard Library Modules: Suppressing C4996 deprecation warnings doesn't work with static constexpr data members"
  • Fixed in 17.7:
    • DevCom-10283892 VSO-1749846 "C++ modules std::expected error C2280 attempting to reference a deleted function"
    • DevCom-10404496 "[C++][Modules] Using std::views::iota in member function in module causes ICE"
  • Fixed in 17.8:
    • DevCom-10404498 VSO-1843798 "[C++][Modules] Using std::views::repeat in member functions gives bogus error about lack of compare header"
    • DevCom-10324326 VSO-1780122 "'...': there are no parameter packs available to expand module"
    • VSO-1475786 "Standard Library Header Units: Deduplication emits bogus errors related to numeric_limits"
      • Fixed at some point between VS 2022 17.1 and 17.8.
    • VSO-1593161 "Standard Library Modules: ctype<char>::table_size should be a compile-time constant"
  • Fixed in 17.9:
    • DevCom-10359857 VSO-1817670 "[C++][Modules] std::mdspan is unusable with C++20 modules"
    • DevCom-10452770 VSO-1877720 "Bug with using modules and getting error "multiple defined std::basic_string_view symbols""
    • DevCom-1359160 VSO-1291691 "Compilation fails when both C++ Modules and Address Sanitizer are present"
  • Fixed in 17.10:
    • VSO-1592395 "Standard Library Modules: <chrono> year_month_weekday and year_month_weekday_last emit bogus error C2131: expression did not evaluate to a constant"
    • VSO-1555263 "Standard Library Header Units: Local array with day{31} initializers emits 'not yet implemented' internal compiler error"
    • VSO-1913621 "extern "C++" doesn't avoid all problems when mixing includes and imports"
    • VSO-1914077 "Modules: extern "C++" interferes with ADL"
    • DevCom-10452704 VSO-1880921 "[Feedback][std:c++latest] C++ compile error when both including a header and calling std::filesystem::path::generic_string() in a module unit"
    • DevCom-10542001 VSO-1930627 "error C1116 unrecoverable error importing module 'std' when constructing and exporting a std::chrono::zoned_time object"
      • Duplicate: VSO-1951431 "Standard Library Modules: chrono::time_point formatting emits bogus error C3861: '_Fill_tm': identifier not found"
      • Duplicate: VSO-1951433 "Standard Library Modules: utc_clock::now() emits fatal error C1116: unrecoverable error importing module 'std'."
    • VSO-1538698 "Better handling for non-exported friend function declarations"
    • VSO-1975579 "Standard Library Modules: fatal error C1116: unrecoverable error importing module 'std'. Specialization of 'std::invoke_result_t' with arguments '_Fn, _Ty...'"
    • DevCom-10519854 VSO-1919553 "Using std::views::zip with std::views::iota in C++20 module results in C1001 Internal compiler error"
  • Fixed in 17.12:
    • DevCom-10506520 VSO-1912515 "Partial specialization of std::formatter in module is not found in other module."
    • #4826
    • DevCom-10652168 VSO-2053126 "C++ modules: Internal compiler error when using std::stacktrace"
    • DevCom-10313766 VSO-1775715 "Using std::format in a module requires including <format> header in .cpp files using that module"
  • Fixed in 17.13:
    • VSO-2293247 "/Zc:preprocessor does not terminate macro definitions properly"
      • This affected /scanDependencies for header units
  • Fixed in 17.14:
    • DevCom-10755613 VSO-2267438 "A custom formatter and a module raise errors in __msvc_formatter.hpp"
  • Fixed in MSVC Build Tools 14.51:
    • (UCRT) OS-33790456 "static inline functions cannot be called when using modules"
      • Bug bash report: https://github.com/StephanTLavavej/STL/issues/21

:building_construction: Building Deduplicated Header Units

Here's the part of our Python-powered test harness that builds "deduplicated" header units by topologically sorting them:

https://github.com/microsoft/STL/blob/ef62d3fa0b8e4e2406b9bb74e916e1ca8a1df802/tests/std/tests/P1502R1_standard_library_header_units/custom_format.py#L56-L109

With a bit of work, this can be extracted into a standalone Python script. (With significantly more work, it could be converted into CMake.)

StephanTLavavej avatar Feb 24 '21 04:02 StephanTLavavej

Great to see the note that std lib modules are ready for production use (as of VS2022 17.5, MSVC only). Does that mean that the statement shown here in the documentation about not using preview releases in production code, should be removed? https://learn.microsoft.com/en-us/cpp/cpp/tutorial-import-stl-named-module?view=msvc-170#prerequisites

CodePagesNet avatar Jun 13 '23 07:06 CodePagesNet