Fix build with Cl and C++20

[jorisv]

Fix #367

Cl compiler doesn't expand __VA_ARGS__ like clang or gcc. It's well documented but hard to catch.

@aescande have introduce the __VEG_PP_ID macro to overcome this issue without activating the /Zc:preprocessor compiler flags.

TODO

• Find a fix
• Activate cl CI steps to avoid regression

[alxbilger]

Hi @jorisv, thanks a lot for the fix. Just curious, how is this related to C++20?

[jorisv]

Hello @alxbilger,

It's maybe related to some C++20 specific branch in our code base.

Code like this one can maybe trigger this issue:

#ifdef VEG_WITH_CXX20_SUPPORT
#define VEG_CPP20(...) __VA_ARGS__
#else
#define VEG_CPP20(...)
#endif

I will not dig into the root cause since the fix allow to use the __VEG_IMPL_PARAM_EXPAND in the same way with clang/g++/cl.

[alxbilger]

I see. Thanks for the clarification