[meaty]

Mainly GCC specific features. No C99 there.

The book should have the word "GNU" wedged in it.

I'd like to have seen some discussion of llvm/clang as well.

[snogglethorpe]

clang and gcc are not very different from a user's point of view—clang deliberately supports a large number of gcc extensions and command-line options. For that matter, so do other C compilers (e.g. the EDG front-end, used by the intel C compiler).

So really these days "gcc" is as much a common dialect of C as it is a particular compiler.