Comment by teo_zero

> A modern C11 library

I'd say "mostly C11": it uses __VA_OPT__ that's been standardized only in C23.

The "foreach" macros need a lot of refinement: passing the body in the parameters is asking for troubles, for example. And using a non-unique default name for the index prevents nested loops.

To overcome the issues with generic and qualified types, have you considered using typeof_unqual?

  _Generic(*(typeof_unqual(x)*)0, ...)