8cc.cr

8cc.cr is compile-time C Compiler implemented as Crystal macros. This is a port of 8cc built on ELVM Infrastructure.

Crystal macros are compile-time evaluation feature to avoid boilerplate code. There are if-sentences, for-loops, integers, strings, arrays, hashes, some control structures and data structures in Crystal macros. We can program on it enough!

For example, you have such a C code as hello.c:

int putchar(int c);

int main(void) {
  char *s = "Hello, World!\n";
  for (; *s; s++) {
    putchar(*s);
  }
  return 0;
}

You can compile it by those commands (by the way, this process wants too long time. You can drink 10 or more cups of tee :-)

$ # Compile C code to assembly language (EIR, ELVM intermediate representation).
$ cat hello.c | crystal build --no-codegen src/8cc.cr > hello.eir

$ # Then, generate binary from this assembly.
$ (echo x86; cat hello.eir) | crystal build --no-codegen src/elc.cr > hello

$ # Run it!
$ chmod +x hello; ./hello
Hello, World!

Surprising point is passing --no-codegen flag to crystal build command, this flag lets crystal build not generate binary, only compile. In short, src/8cc.cr and src/elc.cr are working on only compile-time.

And I made bin/8cc.cr simple shell script, which is compiler-driver for src/8cc.cr and src/elc.cr. It compiles C code and generate binary (or some language codes) automatically. I recommend to use it instead of typing above commands.

Usage

$ ./bin/8cc.cr -h
usage: ./bin/8cc.cr [-s] [-S] [-t target] [-o output] source

options:
  -s               display statistics
  -S               only compile C to ELVM IR, not generate code
  -t target        specify target to compile (i.e. x86, c, cr, js...) [default: c]
  -o output        specify output file name                           [default: ${source%.*}.$target]
  source           specify compiled source file name                  [required]

$ ./bin/8cc.cr -t x86 -o hello hello.c
$ chmod +x hello; ./hello
Hello, World!

NOTE: x86 binary is only worked on Linux.

How was 8cc.cr generated?

You know, I didn't create src/8cc.cr and src/elc.cr by hand-writing. It is just generated.

ELVM (EsoLang VM Compiler Infrastructure) project is awesome. It provides 8cc, which is compiler from C to EIR, and elc, which is generator from EIR to some programming languages code. I wrote Crystal macros target driver for elc at first, then compiled 8cc by 8cc (first 8cc is compiled by usual C compiler like gcc) and generated Crystal code of 8cc by elc (first elc is also compiled).

Author

TSUYUSATO "MakeNowJust" Kitsune make.just.on@gmail.com

More interesting

• rui314/8cc - Small C11 compiler
• shinh/elvm - EsoLang VM Compiler Infrastructure
• variations of 8cc port
  • rhysd/8cc.vim - port for Vim script
  • hak7a3/8cc.tex - port for TeX
  • kw-udon/constexpr-8cc - port for C++ constexpr

Thank you all!