Use C2Rust to convert static inlines

Depends on immunant/c2rust#291. Is exploratory
work for rust-lang/rust-bindgen#1344.

Author: chrysn

Cargo.toml

@@ -15,3 +15,4 @@ license = "LGPL-2.1"
 [build-dependencies]
 bindgen = "0.53.1"
 shlex = "0.1.1"
+serde_json = "1"

build.rs

@@ -5,6 +5,8 @@ use bindgen::builder;
 use std::env;
 use std::path::PathBuf;
 
+use serde_json::json;
+
 fn main() {
     let cflags = env::var("RIOT_CFLAGS")
         .expect("Please pass in RIOT_CFLAGS; see README.md for details.");
@@ -14,7 +16,7 @@ fn main() {
     println!("cargo:rerun-if-env-changed=RIOT_CFLAGS");
     println!("cargo:rerun-if-changed=riot-all.h");
 
-    let cflags = cflags.iter().filter(|x| {
+    let cflags: Vec<String> = cflags.into_iter().filter(|x| {
         match x.as_ref() {
             // non-clang flags showing up with arm cortex m3 (eg. stk3700 board)
             "-Werror" => false,
@@ -30,12 +32,12 @@ fn main() {
             // accept all others
             _ => true,
         }
-    });
+    }).collect();
 
     let bindings = builder()
         .header("riot-all.h")
         .size_t_is_usize(true)
-        .clang_args(cflags)
+        .clang_args(&cflags)
         .use_core()
         .ctypes_prefix("libc")
         .impl_debug(true)
@@ -48,4 +50,73 @@ fn main() {
     bindings
         .write_to_file(out_path.join("bindings.rs"))
         .expect("Couldn't write bindings!");
+
+    // Build a compile_commands.json, and run C2Rust
+    //
+    // The output is cleared beforehand (for c2rust no-ops when an output file is present), and the
+    // input is copied to OUT_DIR as that's the easiest way to get c2rust to put the output file in
+    // a different place.
+
+    let headercopy = out_path.join("riot-c2rust.h");
+    let output = out_path.join("riot_c2rust.rs");
+    println!("cargo:rerun-if-changed=riot-c2rust.h");
+    std::fs::copy("riot-c2rust.h", headercopy)
+        .expect("Failed to copy over header file");
+    match std::fs::remove_file(&output) {
+        Ok(_) => (),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => (),
+        Err(e) => panic!("Failed to remove output file: {}", e),
+    }
+
+    let arguments: Vec<_> = core::iter::once("any-cc".to_string())
+        .chain(cflags.into_iter())
+        .chain(core::iter::once("riot-c2rust.h".to_string()))
+        .collect();
+    let compile_commands = json!([{
+        "arguments": arguments,
+        "directory": out_path,
+        "file": "riot-c2rust.h",
+    }]);
+    let compile_commands_name = out_path.join("compile_commands.json");
+
+    let mut compile_commands_file = std::fs::File::create(compile_commands_name.clone())
+        .expect("Failed to create compile_commands.json");
+    serde_json::to_writer_pretty(&mut compile_commands_file, &compile_commands)
+        .expect("Failed to write to compile_commands.json");
+    compile_commands_file.sync_all()
+        .expect("Failed to write to compile_commands.json");
+
+    let compile_commands_name = compile_commands_name.to_str().expect("Inexpressible path name");
+    // FIXME: This does not rat on the used files. Most are probably included from riot-all.h
+    // anyway, tough.
+    println!("Running C2Rust on {}", compile_commands_name);
+    let status = std::process::Command::new("c2rust")
+        .args(&["transpile", compile_commands_name, "--preserve-unused-functions", "--emit-modules", "--emit-no-std"])
+        .status()
+        .expect("C2Rust failed");
+    if !status.success() {
+        println!("cargo:warning=C2Rust failed with error code {}, exiting", status);
+        std::process::exit(status.code().unwrap_or(1));
+    }
+
+    // Some fix-ups to the C2Rust output
+    // (could just as well call sed...)
+
+    use std::io::{Read, Write};
+
+    let mut rustcode = String::new();
+    std::fs::File::open(output)
+        .expect("Failed to open riot_c2rust.rs")
+        .read_to_string(&mut rustcode)
+        .expect("Failed to read from riot_c2rust.rs");
+
+    rustcode = rustcode.replace("use ::libc;\n", "");
+    rustcode = rustcode.replace(r#"unsafe extern "C" fn "#, r#"pub unsafe extern "C" fn "#);
+
+    let output_replaced = out_path.join("riot_c2rust_replaced.rs");
+    std::fs::File::create(output_replaced)
+        .expect("Failed to create riot_c2rust_replaced.rs")
+        .write(rustcode.as_bytes())
+        .expect("Failed to write to riot_c2rust_replaced.rs");
+
 }

riot-c2rust.h

@@ -0,0 +1,22 @@
+#include <shell.h>
+#include <thread.h>
+#include <irq.h>
+#include <stdio_base.h>
+#include <periph/adc.h>
+#include <periph/gpio.h>
+#include <periph/i2c.h>
+// #include <net/gnrc.h>
+// #include <net/gnrc/udp.h>
+#include <net/gnrc/pktbuf.h>
+// #include <net/gnrc/ipv6.h>
+#include <net/gnrc/nettype.h>
+#include <net/gnrc/netapi.h>
+
+#include <saul.h>
+#include <saul_reg.h>
+
+#include <board.h>
+// #include <xtimer.h>
+
+// not in riot-all?
+#include <mutex.h>

src/inline.rs

@@ -0,0 +1,13 @@
+/// Contains header code converted to Rust by C2Rust
+///
+/// Types in here are distinct from those created in the main module (using bindgen); unifying
+/// those will be part of [bindgen's #1334], but it's a long way there.
+///
+/// [bindgen's #1334]: https://github.com/rust-lang/rust-bindgen/issues/1344
+///
+/// Use these functions through the re-export in the main module, for the C headers may flip-flop
+/// between static inline and linked.
+
+use crate::libc;
+
+include!(concat!(env!("OUT_DIR"), "/riot_c2rust_replaced.rs"));

src/lib.rs

@@ -5,4 +5,11 @@
 
 pub mod libc;
 
+pub mod inline;
+pub use inline::*;
+
+// This is not moved into a dedicated linked module that'd be reexported in analogy to the inline,
+// for that'd need explicit `pub use linked::mutex_t` etc for every type that's present in both and
+// thus not imported for either. As long as this is inlined here, linked types (which are
+// predominantly used so far) take precedence automatically.
 include!(concat!(env!("OUT_DIR"), "/bindings.rs"));