> Most parts of the library are written in pure C99. There are however, some additional components that require C11 to work (notably in the Threading module). As long as you are using minimal version (ZPL_NANO), and manually enable modules, the C99 support should be just fine.

I think it would be better to describe it as a C11 library. I didn't know what to make of 'almost C99', which might refer to limited use of compiler-specific features, for instance.