Well it all starts with testing Upp code for C++20 compliance. let's try theide first. The ide compiles fine on both GCC and CLANG with -std=c++20 option, except some complaints on capturing this by default is deprecated in C++20, which are easy to fix or safe to ignore for now. But it's a total different story with MSC. with standard set to C++17, MSC rejects a bunch of stuff like

return somecondition? "a literal string" : AString;

These are also easy to fix if you don't mind your local version is slightly different from the main stream.

When standard is set to C++20 or c++latest, Upp::Moveable AssertMoveable0() is start to causing compilation failure, this one seems to be quite difficult to fix.

I was thinking it's just a mechanism to communicate to the compiler that it can treat object of this class as raw bytes, maybe we can do it differently with so much more facilities available in more recent c++ library.

So I start to do some experiment.