Core guidelines, conference talks, books, online articles, etc. are not authoritative. If I really want to know if my C code is correct C, I consult the standard. If the standard and an online article disagrees, the article is wrong, definitionally.
Correction: if you want to know if your compiler is correct, you look at the ISO standard. But even as a compiler writer, the ISO standard is not exhaustive. For example the ISO standard doesn't define stuff like include directories, static or dynamic linking, etc.
