All C code I write in the books is currently to the C99 standard. All the compilers involved (Visual C++ on Windows and Clang on Ubuntu) support C99 but C11 support seems restricted to GCC and Clang.
Microsoft has traditionally supported C++ but their C support seems a bit grudging; realistically they don’t prioritise it which I can understand.
Given though that I’m not going to republish my first e-book for a while (I’d like to add a WebAssembly chapter or two first), I’m going to investigate whether it’s worth switching to C11 for the 2nd book. From what I’ve read all it needs is a flag to tll it to compile to C11 standards. This is for Clang.
But the other question is what will I gain by doing this and I can’t actually see there’s that much benefit.. I don’t need Unicode, I don’t think alignment will really make much difference. You can read about the C11 changes on WikiChip.
So I’ve made the decision. I’ll stick with C99 for now. But for an alternative view, I recommend Danny Kalev’s 2012 article on C11.