C4 – C in 4 functions

Pretty damn impressive.

Though I must wonder: how complete is it? What does it and does it not support? It's at least complete enough to be self-hosting, but beyond that? The code doesn't use that much of C.

Judging from the comments in c4.cpp, it probably only supports enough of a subset to compile itself.

Granted, while building a parser that can parse (let alone compiling) the full C language is nontrivial, any undergrad should be able to build a parser and compiler for a sufficiently simple subset of it. (In my undergrad, we used this subset to build a "compiler" in second year: https://www.student.cs.uwaterloo.ca/~cs241/wlp4/WLP4.html)

You can build a C parser in an afternoon. It only has a few language constructs. Declarations are the hardest. Scanners are readily available for expressions and constants.

C is not a simple language as a CIL guy says [1]. I wrote my own C compiler [2] and I can say that writing a parser was harder than I thought. It would take more than half a day at least.

[1] http://www.cs.berkeley.edu/~necula/cil/cil016.html [2] https://github.com/rui314/8cc