C++/WinRT UWP App fails to compile when using C++20

[JuliusZet]

Hello

I would like to use the Boost 1.80 Header-Only Libraries in my C++/WinRT UWP App. But when I switch the C++ Language Standard to "ISO C++20 Standard (/std:c++20)", then the app will not compile anymore.

I get the following output:

Build started...
1>------ Build started: Project: BlankApp1, Configuration: Debug x64 ------
1>App.cpp
1>MainPage.cpp
1>C:\Users\juliuszet\source\repos\BlankApp1\BlankApp1\boost\signals2\detail\lwm_win32_cs.hpp(61,49): error C2371: 'InitializeCriticalSectionEx': redefinition; different basic types (compiling source file MainPage.cpp)
1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\um\synchapi.h(155): message : see declaration of 'InitializeCriticalSectionEx' (compiling source file MainPage.cpp)
1>C:\Users\juliuszet\source\repos\BlankApp1\BlankApp1\boost\signals2\detail\lwm_win32_cs.hpp(61,49): error C2733: 'InitializeCriticalSectionEx': you cannot overload a function with 'extern "C"' linkage (compiling source file MainPage.cpp)
1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\um\synchapi.h(155,1): message : see declaration of 'InitializeCriticalSectionEx' (compiling source file MainPage.cpp)
1>C:\Users\juliuszet\source\repos\BlankApp1\BlankApp1\boost\signals2\detail\lwm_win32_cs.hpp(61,49): error C2371: 'InitializeCriticalSectionEx': redefinition; different basic types (compiling source file App.cpp)
1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\um\synchapi.h(155): message : see declaration of 'InitializeCriticalSectionEx' (compiling source file App.cpp)
1>C:\Users\juliuszet\source\repos\BlankApp1\BlankApp1\boost\signals2\detail\lwm_win32_cs.hpp(61,49): error C2733: 'InitializeCriticalSectionEx': you cannot overload a function with 'extern "C"' linkage (compiling source file App.cpp)
1>C:\Program Files (x86)\Windows Kits\10\Include\10.0.19041.0\um\synchapi.h(155,1): message : see declaration of 'InitializeCriticalSectionEx' (compiling source file App.cpp)
1>C:\Program Files (x86)\Windows Kits\10\bin\10.0.19041.0\XamlCompiler\Microsoft.Windows.UI.Xaml.Common.targets(486,5): error MSB4181: The "CompileXaml" task returned false but did not log an error.
1>Done building project "BlankApp1.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Steps to reproduce:

1. Create a new project in Visual Studio 2022. Project template: "Blank App (C++/WinRT)". Do not change any settings during the project creation.
2. Copy the "boost_1_80_0.7z\boost_1_80_0\boost" folder into your project directory (where your BlankApp1.vcxproj) is located. For me the path is "C:\Users\juliuszet\source\repos\BlankApp1\BlankApp1" <-- boost folder goes here.
3. Add #include <boost/signals2.hpp> to your MainPage.h file, right below the #include "MainPage.g.h".
4. Click Build --> Build Solution and notice, that it compiles successfully.
5. Click Project --> Properties, Navigate to Configuration Properties --> C/C++ --> Language and change the C++ Language Standard to "ISO C++20 Standard (/std:c++20)".
6. Click Build --> Build Solution and notice, that it does not compile anymore.

After taking a closer look at the error messages in the output, I played around a bit and found out, that it does compile again, when changing a few lines of code in "boost\signals2\detail\lwm_win32_cs.hpp"

replace this:

#if BOOST_PLAT_WINDOWS_RUNTIME
extern "C" __declspec(dllimport) void __stdcall InitializeCriticalSectionEx(::_RTL_CRITICAL_SECTION *, unsigned long, unsigned long);
#else
extern "C" __declspec(dllimport) void __stdcall InitializeCriticalSection(::_RTL_CRITICAL_SECTION *);
#endif

with this:

extern "C" __declspec(dllimport) void __stdcall InitializeCriticalSection(::_RTL_CRITICAL_SECTION *);

and replace this:

#if BOOST_PLAT_WINDOWS_RUNTIME
        boost::signals2::detail::InitializeCriticalSectionEx(reinterpret_cast< boost::signals2::detail::rtl_critical_section* >(&cs_), 4000, 0);
#else
        boost::signals2::detail::InitializeCriticalSection(reinterpret_cast< boost::signals2::detail::rtl_critical_section* >(&cs_)); 
#endif

with this:

        boost::signals2::detail::InitializeCriticalSection(reinterpret_cast< boost::signals2::detail::rtl_critical_section* >(&cs_)); 

Could someone have a look at this to find out what the issue is and who is at fault here?

Thank you very much in advance and have an awesome day! :)

Kind regards JuliusZet