Rust and the C preprocessor.

I'm a long time C and C++ programmer.

And I enjoy using the C preprocessor also.

Trying out Rust.

But I must have those "tables", and the Rust macros are not good, so I must have the C preprocessor.

Cargo.toml:

[build-dependencies]
cc = "1.0"

build.rs:

use std::env;
use std::fs::File;
use std::io::Write;
use std::path::Path;
extern crate cc;

fn main() {
 let out_dir = env::var("OUT_DIR").unwrap();
 let dest_path = Path::new(&out_dir).join("wasm_instructions.rs");
 let mut f = File::create(&dest_path).unwrap();

 let c = &mut cc::Build::new();
 c.flag("-I.").file("src/wasm_instructions.h");
    
 // Preprocess w/o line numbers
 // -EP for Visual C++
 // -E -P for gcc
 //
 // TODO Compiler detection.
 //
 // Nothing works, so remove line directives ourselves.

 for s in String::from_utf8(c.expand()).unwrap().lines() {
  let bytes = s.as_bytes();
  if bytes.len() > 0 && bytes [0] != b'#' {
   f.write(bytes).unwrap();
   f.write(b"\n").unwrap();
  }
 }
}

The .h file looks like this:

#ifdef FOO


FOO(...)
FOO(...)



#else

#undef FOO
#define FOO(...)
#include __FILE__



#undef FOO
#define FOO(...)
#include __FILE__

#endif