One alternative is LCC: https://en.wikipedia.org/wiki/LCC_(compiler) https://en.wikipedia.org/wiki/LCC_(compiler) It is half way in complexity between TCC and

One alternative is LCC: https://en.wikipedia.org/wiki/LCC_(compiler) https://en.wikipedia.org/wiki/LCC_(compiler) It is half way in complexity between TCC and GCC or LLVM and was created to be educational. I think there are major differences between more recent versions and what it described in the book.