Microsoft C++ docs: What's new for October 2021

This article lists major changes to the Microsoft C++ docs July 2021 through October 2021.

• For what was new in the docs in previous months, see What's new history.
• For what's new related to C++ in Visual Studio, see What's new for C++ in Visual Studio.
• For the latest C and C++ conformance with ISO standards status, see C++ conformance improvements in Visual Studio.

Active Template Library (ATL), Microsoft Foundation Classes (MFC)

Updated articles

• CSimpleStringT Class - updated code examples and added code example output
• MFC class hierarchy chart - Update MFC hierarchy chart

C language

New articles

• Generic selection (C11)

Updated articles

• register storage-class specifier - Add C5033 warning
• C Pragmas - Add system_header pragma documentation
• C Bit Fields - Clarify int main(void) example & document MSVC doesn't straddle bit-fields

C runtime library

Updated articles

• CRT Initialization - Add 16.11 Compiler warnings C5247 and C5248
• rand - Update code example
• wcstombs_s, _wcstombs_s_l - Update code example
• _get_errno - Update code example

C/C++ compiler and tools errors and warnings

New articles

• Command-line error D8049
• Compiler Warning C5243
• Compiler Warning C5247
• Compiler Warning C5248
• Compiler Warning (level 1) C5033

Updated articles

• Command-line errors and warnings - new error messages
• Compiler Warning (level 4) C4710 - Add C5033 warning
• Compiler Warnings C4800 through C5999 - Add compiler warning C5033, C5243, C5249, C5250, C5247, and C5248.
• Compiler Error C2666 - Update 16.1 conformance
• Compiler Warning (level 4) C4702 - Update warning C4702
• Compiler Error C2440 - Add /Zc:char8_t compiler option
• Compiler Error C2760 - New /Zc:lambda info
• Compiler Error C2259 - Update code example

C/C++ compiler intrinsics and assembly language

New articles

• MASM instruction format
• OPTION AVXENCODING
• OPTION LANGUAGE

Updated articles

• MASM for x64 (ml64.exe) - Document MASM instruction format including prefixes and option avxencoding
• Microsoft Macro Assembler reference - Document MASM instruction format including prefixes and option avxencoding
• OPTION - Document MASM instruction format including prefixes and option avxencoding
• _InterlockedCompareExchange intrinsic functions - Adding missing interlocked intrinsic and fixing another interlock intrinsic return type

C/C++ in Visual Studio overview

New articles

• C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2019
• What's new for C++ in Visual Studio 2019

Updated articles

• Overview of C++ development in Visual Studio - Visual Studio 2022 related updates.
• Install C11 and C17 support in Visual Studio - Visual Studio 2022 related updates, C17 updates
• C++ Tools and Features in Visual Studio Editions - Visual Studio 2022 related updates, C17 updates
• C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2022 - Visual Studio 2022 and 16.1 conformance updates
• Microsoft C/C++ language conformance by Visual Studio version - Visual Studio 2022 related updates
• C and C++ in Visual Studio - Add missing redist content

C/C++ preprocessor reference

New articles

• system_header pragma

Updated articles

• fenv_access pragma - Add floating-point contractions info
• float_control pragma - Add floating-point contractions info
• fp_contract pragma - Add floating-point contractions info
• Predefined macros - Add __SANITIZE_ADDRESS__ and _M_FP_CONTRACT
• Compiler warnings that are off by default - Add compiler warning C5243, C5249, C5250, C5247, and C5248

C/C++ projects and build systems

New articles

• /Zc:char8_t (Enable C++20 char8_t type)
• /Zc:lambda (Enable updated lambda processor)
• /fsanitize-coverage (Configure sanitizer coverage)
• abspath NMAKE function
• basename NMAKE function
• filter, filteri NMAKE functions
• filterout, filterouti NMAKE functions
• findstring, findstringi NMAKE functions
• patsubst, patsubsti NMAKE functions
• strip NMAKE function
• subst, substi NMAKE functions
• Walkthrough: Build and debug C++ with WSL 2 and Visual Studio 2022

Updated articles

• Configure and build with CMake Presets in Visual Studio - Fix inconsistencies and add documentation about the "unspecified" architecture feature
• Clang/LLVM support in Visual Studio CMake projects - Clarified version-specific installation
• CMake projects in Visual Studio - Fix inconsistencies in CMake docs and add docs on using existing cache without cmake-server
• /fp (Specify floating-point behavior) - Fix /fp sample code
• /Og (Global Optimizations) - Clarify when the register keyword is ignored
• /PROFILE (Performance Tools Profiler) - Address /profile issues
• Use the Microsoft C++ toolset from the command line - Fix MSBuild recommendation & update C/C++ workload name
• Use an NMAKE macro - Add documentation for the new NMAKE functions
• Commands in a makefile - Combine and update NMAKE docs
• NMAKE makefile contents and features - Combine and update NMAKE docs
• Create a C++ makefile project - Combine and update NMAKE docs
• Define an NMAKE macro - Combine and update NMAKE docs
• Dot directives - Combine and update NMAKE docs
• Inference rules - Combine and update NMAKE docs
• Inline files in a makefile - Combine and update NMAKE docs
• Makefile Preprocessing - Combine and update NMAKE docs
• NMAKE Reference - Combine and update NMAKE docs
• Running NMAKE - Combine and update NMAKE docs
• Sample Makefile - Combine and update NMAKE docs
• Special NMAKE macros - Combine and update NMAKE docs
• Configuring Programs for Windows XP - Link updates for new redist article
• /Zc (Conformance) - New /Zc:lambda information
• /Zc:__cplusplus (Enable updated __cplusplus macro) - New /Zc:lambda information
• CMake predefined build configurations - Fix inconsistencies in CMake docs
• CMakePresets.json and CMakeUserPresets.json Microsoft vendor maps - Fix inconsistencies in CMake docs
• Tutorial: Debug a CMake project on a remote Windows machine - Fix inconsistencies in CMake docs
• CMakeSettings.json schema reference - Fix inconsistencies in CMake docs
• launch.vs.json schema reference (C++) - add debugInfo macro definitions
• /external (External headers diagnostics) - Add system_header pragma doc
• DUMPBIN Reference - Setting PATH allows DUMPBIN to be executed from the command prompt
• /Qspectre - Clarified /Qspectre Required Libraries section

C++ in Visual Studio

Updated articles

• Storage classes - Add C5033 warning
• void (C++) - Clarify overall article
• Labeled statements - Correct labeled statements
• Brace initialization - Address sanitizer comment location
• Member Access Control (C++) - Update static member access in example
• String and character literals (C++) - Updates for C++20 portable char8_t.
• Declarations and definitions (C++) - fix code sample
• Template Specialization (C++) - update code example

C++ in Visual Studio tutorials

Updated articles

• Create a console calculator in C++ - add Git source control info to the tutorial

C++ porting and upgrade guide

Updated articles

• C++ binary compatibility between Visual Studio versions - Update version info

C++ Standard Library (STL)

New articles

• ambiguous_local_time class
• choose enum
• clock_time_conversion struct
• file_clock class
• gps_clock class
• is_clock structure
• last_spec struct
• local_info struct
• local_t struct
• nonexistent_local_time class
• sys_info struct
• tai_clock class
• time_zone_link class
• tzdb_list class
• tzdb struct
• utc_clock class
• zoned_time class
• zoned_traits struct

Updated articles

• <chrono> functions - added new <chrono> functions
• <chrono> - added new <chrono> types
• duration class - overall article update and linking to related non-member functions
• Using Insertion Operators and Controlling Format - fix setw code example
• <chrono> operators - Added new C++20 chrono operators
• local_info struct - updated descriptions for errors
• time_zone class - article clarifications
• any class - Added requirements section
• <any> functions - Added requirements section
• bad_any_cast class - Added requirements section
• domain_error Class - Improve <stdexcept> documentation and examples
• invalid_argument Class - Improve <stdexcept> documentation and examples
• length_error Class - Improve <stdexcept> documentation and examples
• logic_error Class - Improve <stdexcept> documentation and examples
• out_of_range Class - Improve <stdexcept> documentation and examples
• overflow_error Class - Improve <stdexcept> documentation and examples
• range_error Class - Improve <stdexcept> documentation and examples
• runtime_error Class - Improve <stdexcept> documentation and examples
• underflow_error Class - Improve <stdexcept> documentation and examples
• filesystem - <filesystem> no longer includes <experimental/filesystem>
• Output File Stream Member Functions - fixed code example
• <bit> functions - Fixed code example
• <execution> - Mention limits of concurrency
• <future> functions - Mention limits of concurrency
• thread Class - Mention limits of concurrency

Overview of Windows programming in C++

New articles

• Microsoft Visual C++ Redistributable Latest Supported Downloads

Updated articles

• Walkthrough: Create a traditional Windows Desktop application (C++) - updated examples

Read and write code using C++ in Visual Studio

New articles

• IntelliSense code linter for C++ overview
• lnt-assignment-equality
• lnt-integer-float-division
• lnt-accidental-copy
• lnt-arithmetic-overflow
• lnt-logical-bitwise-mismatch
• lnt-uninitialized-local

Updated articles

• lnt-integer-float-division - Add Visual Studio 2022 specific config information

STL/CLR library reference

Updated articles

• .NET programming with C++/CLI - updated instructions for Visual Studio version UI differences

Community contributors

The following people contributed to the C++, C, and Assembler docs during this period. Thank you! See Microsoft Docs contributor guide overview if you'd like to learn how to contribute.

• mohammad-ghasemi-dev (5)
• Jaiganeshkumaran - Jaiganesh Kumaran (2)
• workingjubilee - Jubilee (2)
• adr26 (1)
• AlexGuteniev - Alex Guteniev (1)
• AzAgarampur - Arush Agarampur (1)
• d-c-d - David Dyck (1)
• onihusube (1)
• rayz-bee - rayz-bee (1)
• redteamrover (1)
• RibShark (1)
• sauparna - Sauparna Palchowdhury (1)
• sudoerChris - Chris Ho (1)
• thispsj - PSJ (1)
• Veverke - Avraham (1)
• weijiechai - Chai Wei Jie (1)
• wmcnamara - Weston McNamara (1)
• ystamant (1)

What's new history

The following section provides the previous update of what's new in the Visual Studio docs.

June 2021

Build insights

New articles

• HeaderUnit class
• Module class
• PrecompiledHeader class
• TRANSLATION_UNIT_TYPE enum
• TRANSLATION_UNIT_TYPE_DATA enum
• TranslationUnitType class

Updated articles

• C++ Build Insights SDK: event table - add new C++ Build Insights events
• Get started with C++ Build Insights - add new C++ Build Insights events

C language

Updated articles

• _Static_assert keyword and static_assert macro (C11) - update the SDK to use
• Alignment (C11) - update the SDK to use
• Generic selection (C11) - update the SDK to use

C runtime library

Updated articles

Many articles were updated to prevent the machine translation of code elements.

• _cprintf_p, _cprintf_p_l, _cwprintf_p, _cwprintf_p_l - printf() rounding behavior change
• _cprintf_s, _cprintf_s_l, _cwprintf_s, _cwprintf_s_l - printf() rounding behavior change
• _cprintf, _cprintf_l, _cwprintf, _cwprintf_l - printf() rounding behavior change
• _fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l - printf() rounding behavior change
• _get_printf_count_output - printf() rounding behavior change
• _printf_p, _printf_p_l, _wprintf_p, _wprintf_p_l - printf() rounding behavior change
• _scprintf_p, _scprintf_p_l, _scwprintf_p, _scwprintf_p_l - printf() rounding behavior change
• _scprintf, _scprintf_l, _scwprintf, _scwprintf_l - printf() rounding behavior change
• _vcprintf_p, _vcprintf_p_l, _vcwprintf_p, _vcwprintf_p_l - printf() rounding behavior change
• _vcprintf_s, _vcprintf_s_l, _vcwprintf_s, _vcwprintf_s_l - printf() rounding behavior change
• _vscprintf, _vscprintf_l, _vscwprintf, _vscwprintf_l - printf() rounding behavior change
• _vsprintf_p, _vsprintf_p_l, _vswprintf_p, _vswprintf_p_l - printf() rounding behavior change
• _snprintf_s, _snprintf_s_l, _snwprintf_s, _snwprintf_s_l - printf() rounding behavior change
• errno constants - improve readability
• fprintf, _fprintf_l, fwprintf, _fwprintf_l - printf() rounding behavior change
• freopen_s, _wfreopen_s - new C11 flags
• freopen, _wfreopen - added C11 flags
• pow, powf, powl - note change to pow(T,int) starting in VS 2015 update 1
• printf_s, _printf_s_l, wprintf_s, _wprintf_s_l - printf() rounding behavior change
• setlocale, _wsetlocale - clarified UTF-8 string mode
• sprintf, _sprintf_l, swprintf, _swprintf_l, __swprintf_l - printf() rounding behavior change
• cprintf - printf() rounding behavior change
• fprintf_s, _fprintf_s_l, fwprintf_s, _fwprintf_s_l - printf() rounding behavior change
• sprintf_s, _sprintf_s_l, swprintf_s, _swprintf_s_l - printf() rounding behavior change
• strcpy_s, wcscpy_s, _mbscpy_s, _mbscpy_s_l - fixed code examples
• strncat_s, _strncat_s_l, wcsncat_s, _wcsncat_s_l, _mbsncat_s, _mbsncat_s_l - printf() rounding behavior change
• Type-generic math - updated the SDK version to use
• vprintf, _vprintf_l, vwprintf, _vwprintf_l - printf() rounding behavior change
• vsprintf_s, _vsprintf_s_l, vswprintf_s, _vswprintf_s_l - printf() rounding behavior change

C++ in Visual Studio

Updated articles

• _variant_t::operator= - add remarks for operator= and make the article easier to read.
• Abstract classes (C++) - add Microsoft-specific extension information for inline pure virtual destructor
• Attributes in C++ - add missing errors and warnings: C7000-C7999, C4834
• char, wchar_t, char8_t, char16_t, char32_t - clarified whether char is signed or unsigned

C++ porting and upgrade guide

Updated articles

• Introduction to Microsoft C++ for UNIX Users - Visual Studio 16.10 updates to C17 conformance
• Visual C++ What's New 2003 through 2015 - note change to pow(T,int) starting in VS 2015 update 1

C/C++ compiler and tools errors and warnings

New articles

• Command-line error D8048
• Compiler Error C7510
• Compiler Error C7536
• Compiler errors C7000 through C7499
• Compiler errors C7500 through C7999
• Compiler Warning (error) C4597
• Compiler warning (level 1) C4834
• Compiler Warning (level 1) C5050
• Compiler warning (level 3) C4698
• Compiler Warning (level 3) C4768
• Compiler Warning (level 4) C4841
• Compiler Warning (level 4) C4843
• Compiler warning C5037
• Fatal Error C1090

Updated articles

• Compiler Error C2139 - added some version 2017 diagnostics
• Compiler Error C2201 - added some version 2017 diagnostics
• Compiler Error C2276 - update C2276
• Compiler Error C2668 - added some version 2017 diagnostics
• Compiler Error C2855 - add remarks about how to resolve this error
• Compiler errors C2000 - C3999, C7000 - C7999 - add missing errors and warnings: C7000-C7999, C4834
• Compiler errors C7500 through C7999 - added some version 2017 diagnostics; add error C7510; add missing errors and warnings: C7000-C7999, C4834
• Compiler Warning (level 1) C4179 - added some version 2017 diagnostics
• Compiler Warning (level 1) C5208 and Error C7626 - add missing errors and warnings: C7000-C7999, C4834
• Compiler Warning (level 4) C4189 - added some version 2017 diagnostics
• Compiler Warning C5038 - added some version 2017 diagnostics
• Compiler warnings by compiler version - update Visual Studio 16.10 conformance improvements and new warnings; Add new 16.10 warnings, version info; update version strings for Visual Studio 16.8, 16.9, and 16.10
• Compiler warnings C4400 Through C4599 - added some Visual Studio version 2017 diagnostics
• Compiler warnings C4800 through C5999 - update Visual Studio 16.10 conformance improvements and new warnings; add new 16.10 warnings, version info; added some version 2017 diagnostics; add missing errors and warnings: C7000 - C7999, C4834
• Vectorizer and parallelizer messages - add vectorizer failure reason 505; add 1204 reason code

C/C++ compiler intrinsics and assembly language

Updated articles

• Microsoft Macro Assembler BNF Grammar - cleanup formatting and machine translation issues

C/C++ in Visual Studio overview

New articles

• C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2017
• Microsoft C++ docs: What's new for Visual Studio 16.8
• What's new for C++ in Visual Studio 2017

Updated articles

• C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2017 - added version 2017 diagnostics
• C++ Conformance improvements, behavior changes, and bug fixes in Visual Studio 2019 - Visual Studio 16.10 updates to C17 conformance; update 16.10 conformance improvements and new warnings; add error C7510; add missing errors and warnings: C7000 - C7999, C4834; update conformance docs for 16.9
• C++ in Visual Studio - Visual Studio 16.10 updates to C17 conformance
• Install C11 and C17 support in Visual Studio - Visual Studio 16.10 updates to C17 conformance
• Microsoft C/C++ language conformance by Visual Studio version - Visual Studio 16.10 updates to C17 conformance; update conformance table for Visual Studio 16.10 and Visual Studio 16.9
• Microsoft C++ docs: What's new for Visual Studio 16.8 - Visual Studio 16.10 updates to C17 conformance
• What's new for C++ in Visual Studio 2017 - Visual Studio 16.10 updates to C17 conformance; update Visual Studio 16.9 release conformance docs

C/C++ preprocessor reference

Updated articles

• Compiler warnings that are off by default - update Visual Studio 16.10 conformance improvements and new warnings; added some version 2017 diagnostics
• Predefined macros - add new Visual Studio 16.10 warnings, version info; update version strings for Visual Studio 16.8, 16.9, and 16.10

C/C++ projects and build systems

New articles

• /external (External headers diagnostics)
• /headerName (Build a header unit from the specified header)
• /sourceDependencies:directives (List module and header unit dependencies)
• CMakePresets.json and CMakeUserPresets.json Microsoft vendor maps
• Configure and build with CMake Presets in Visual Studio
• HeaderUnit class
• Module class
• PrecompiledHeader class
• TRANSLATION_UNIT_TYPE enum
• TRANSLATION_UNIT_TYPE_DATA enum
• TranslationUnitType class
• Walkthrough: Build and import header units in Microsoft Visual C++
• Walkthrough: Import STL libraries as header units

Updated articles

• /experimental:module (Enable module support) - new content for header-units
• /Qspectre - update for VS 2019
• /Y (precompiled headers) - new content for header-units
• /analyze (Code analysis) - update with up-to-date options list, add more information, and restructure for better organization of related options
• /await (Enable coroutine support) - add /await:strict for Visual Studio 16.10
• /clr (Common Language Runtime Compilation) - include version for support of /clr:netcore option
• /exportHeader (Create header units) - add new content related to header-units
• /external (External headers diagnostics) - /external not experimental in Visual Studio 16.10
• /F (Set Stack Size) - update for VS 2019
• /FC (Full path of source code file in diagnostics) - Classify behavior by version.
• /GL (Whole program optimization) - fix loc issue in /GL docs
• /headerUnit (Use header unit IFC) - new content for header-units
• /INTEGRITYCHECK (Require signature check) - updated signing guidance for integritycheck binaries
• /openmp (Enable OpenMP Support) - add /openmp:llvm compiler switch docs
• /reference (Use named module IFC) - new content for header-units
• /sourceDependencies (List all source-level dependencies) - new content for header-units
• /std (Specify Language Standard Version) - Visual Studio 16.10 updates to C17 conformance
• /translateInclude (Translate include directives into import directives) - new content for header-units
• Advanced Property Page - add Windows Desktop Compatible property for Visual Studio 16.10; Add LLVM toolset version option for Visual Studio 16.9
• ARM Exception Handling - fix ComputeXdataSize samples for ARM/ARM64
• ARM64 exception handling - fix ComputeXdataSize samples for ARM/ARM64
• C++ Build Insights SDK: event table - add New C++ Build Insights Events to documentation
• Clang/LLVM support in Visual Studio projects - add LLVM toolset version option for Visual Studio 16.9; update clang-support-msbuild.md
• CMake projects in Visual Studio - add advanced details about using CMake file-api
• Compiler options listed alphabetically - new content for header-units
• Compiler options listed by category - new content for header-units
• Configure and build with CMake Presets in Visual Studio - improve readability
• General Property Page (Project) - add Windows Desktop Compatible property for Visual Studio 16.10
• Get started with C++ Build Insights - add New C++ Build Insights Events to documentation
• How to: Modify the Target Framework and Platform Toolset - improve readability
• Open Folder support for C++ build systems in Visual Studio - fix CppProperties.json MinGW-w64 contents
• Unicode support in the compiler and linker - add info about how to save using a different encoding
• Use the Microsoft C++ toolset from the command line - updated for VS 2019
• Walkthrough: Compile a C program on the command line - Visual Studio 16.10 updates to C17 conformance
• Walkthrough: Compiling a Native C++ Program on the Command Line - clarified notepad behavior when opening source file

C++ Standard Library (STL) reference

New articles

• <ranges>
• day class
• month_day_last class
• month_day class
• month_weekday_last class
• month_weekday class
• year_month class

Updated articles

• bitset class - improve readability
• vector class - fix typo in code sample

Code quality

New articles

• C6389: MARK_INTERNAL_OR_MISSING_COMMON_DECL

Updated articles

• C6031 - add note about ignoring a function's return value
• C26432 DEFINE_OR_DELETE_SPECIAL_OPS - update code examples
• C26497 USE_CONSTEXPR_FOR_FUNCTION - add note about when warning won't be issued

Linux with C++ in Visual Studio

Updated articles

• Connect to your target Linux system in Visual Studio - add section about host key verification
• ConnectionManager reference - add note about host key fingerprint flags added in Visual Studio 16.10.

Overview of Windows programming in C++

Updated articles

• Determining Which DLLs to Redistribute - updated for Visual Studio 2019

Parallel programming in C++ in Visual Studio

Updated articles

• C++ AMP Overview - add note about C++ AMP library deprecation
• Walkthrough: Debugging a C++ AMP application - fixed code sample

Community contributors

The following people contributed to the C++, C, and Assembler docs during this period. Thank you! See Microsoft Docs contributor guide overview if you'd like to learn how to contribute.

• 0xbadfca11 (1)
• bclehmann - Benjamin Lehmann (1)
• Brian-Taylor8 (1)
• cartwrightluke (2)
• ccawley2011 - Cameron Cawley (1)
• EddieBreeveld - Edward Breeveld (1)
• FrankAtHexagon - Frank Edwards (1)
• fsb4000 - Igor Zhukov (1)
• Jaiganeshkumaran - Jaiganesh Kumaran (2)
• jayvient - Jayvien (1)
• KishkinJ10 (1)
• kokosxD - kokos (1)
• langemol - Jacco Mol (1)
• MUzairS15 (1)
• nadavsu - Nadav (1)
• NegiAkash890 - Akash Negi (1)
• pjessesco - Jino Park (1)
• pramodkirchki (1)
• Radfordhound - Graham Scott (1)
• sapant-msft (1)
• sebgod - Sebastian Godelet (1)
• seedkar1 (1)
• ShamanCoder (1)
• sheila-stewart (1)
• softmac (1)
• Thieum - Matthieu Penant (2)
• tjs137 (1)
• urmyfaith - zx (1)
• ValZapod - Valerii Zapodovnikov (1)
• westinn - Nicolas Westin (1)