codecvt + std::(w/u16/u32)string support

because this is surprisingly hard using standard C++

Individuals using Visual Studio 2015, or on Windows with the VC++ and MinGW compilers (possibly Clang++ on Windows as well) have <codecvt> headers, and thusly Sol will attempt to include it. Individuals on GCC 4.9.x, Clang 3.5.x, Clang 3.6.x do not seem to have <codecvt> shipped with the standard library that comes with installation of these compilers. If you want std::wstring, std::u16string, std::u32string automatic handling then you need to make sure you have those headers and then define SOL_CODECVT_SUPPORT on unsupported compilers.

Visual C++, in Visual Studio versions 15.5+ (_MSC_VER >= 1912), introduced deprecation macros when you are in /std:c++latest, or similar. In order to get rid of codecvt issues, you need to define the silencing macros they ask for (_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING).

It must be defined because despite the committee deprecating it, there is no useful standard alternative to perform these conversions (without, saying, including <Windows.h> on Windows machines, which is unacceptable).

Note

The standard states the following:

“this library component should be retired to Annex D, along side ,
until a suitable replacement is standardized.”

In other words, it is totally fine! Just define the silencing macro and leave it at that. sol2 keeps up with the standard, so the moment a suitable replacement is standardized it will be added to sol2 posthaste. For the time being, you will be okay.