cli: re-introduce create-exe functionality

lib/cli/src/commands/create_exe.rs

@@ -0,0 +1,293 @@
+//! Create a standalone native executable for a given Wasm file.
+
+use crate::store::CompilerOptions;
+use anyhow::{Context, Result};
+use std::env;
+use std::fs;
+use std::fs::File;
+use std::io::prelude::*;
+use std::io::BufWriter;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use structopt::StructOpt;
+use wasmer::*;
+use wasmer_object::{emit_serialized, get_object_for_target};
+
+const WASMER_MAIN_C_SOURCE: &[u8] = include_bytes!("wasmer_create_exe_main.c");
+
+#[derive(Debug, StructOpt)]
+/// The options for the `wasmer create-exe` subcommand
+pub struct CreateExe {
+    /// Input file
+    #[structopt(name = "FILE", parse(from_os_str))]
+    path: PathBuf,
+
+    /// Output file
+    #[structopt(name = "OUTPUT PATH", short = "o", parse(from_os_str))]
+    output: PathBuf,
+
+    /// Compilation Target triple
+    #[structopt(long = "target")]
+    target_triple: Option<Triple>,
+
+    #[structopt(flatten)]
+    compiler: CompilerOptions,
+
+    #[structopt(short = "m", multiple = true, number_of_values = 1)]
+    cpu_features: Vec<CpuFeature>,
+
+    /// Additional libraries to link against.
+    /// This is useful for fixing linker errors that may occur on some systems.
+    #[structopt(short = "l", multiple = true, number_of_values = 1)]
+    libraries: Vec<String>,
+}
+
+impl CreateExe {
+    /// Runs logic for the `compile` subcommand
+    pub fn execute(&self) -> Result<()> {
+        let target = self
+            .target_triple
+            .as_ref()
+            .map(|target_triple| {
+                let mut features = self
+                    .cpu_features
+                    .clone()
+                    .into_iter()
+                    .fold(CpuFeature::set(), |a, b| a | b);
+                // Cranelift requires SSE2, so we have this "hack" for now to facilitate
+                // usage
+                features |= CpuFeature::SSE2;
+                Target::new(target_triple.clone(), features)
+            })
+            .unwrap_or_default();
+        let (store, compiler_type) = self.compiler.get_store_for_target(target.clone())?;
+
+        println!("Compiler: {}", compiler_type.to_string());
+        println!("Target: {}", target.triple());
+
+        let working_dir = tempfile::tempdir()?;
+        let starting_cd = env::current_dir()?;
+        let output_path = starting_cd.join(&self.output);
+        env::set_current_dir(&working_dir)?;
+
+        #[cfg(not(windows))]
+        let wasm_object_path = PathBuf::from("wasm.o");
+        #[cfg(windows)]
+        let wasm_object_path = PathBuf::from("wasm.obj");
+
+        let wasm_module_path = starting_cd.join(&self.path);
+
+        let module =
+            Module::from_file(&store, &wasm_module_path).context("failed to compile Wasm")?;
+        let bytes = module.serialize()?;
+        let mut obj = get_object_for_target(target.triple())?;
+        emit_serialized(&mut obj, &bytes, target.triple())?;
+        let mut writer = BufWriter::new(File::create(&wasm_object_path)?);
+        obj.write_stream(&mut writer)
+            .map_err(|err| anyhow::anyhow!(err.to_string()))?;
+        writer.flush()?;
+        drop(writer);
+
+        self.compile_c(wasm_object_path, output_path)?;
+
+        eprintln!(
+            "✔ Native executable compiled successfully to `{}`.",
+            self.output.display(),
+        );
+
+        Ok(())
+    }
+
+    fn compile_c(&self, wasm_object_path: PathBuf, output_path: PathBuf) -> anyhow::Result<()> {
+        // write C src to disk
+        let c_src_path = Path::new("wasmer_main.c");
+        #[cfg(not(windows))]
+        let c_src_obj = PathBuf::from("wasmer_main.o");
+        #[cfg(windows)]
+        let c_src_obj = PathBuf::from("wasmer_main.obj");
+
+        {
+            let mut c_src_file = fs::OpenOptions::new()
+                .create_new(true)
+                .write(true)
+                .open(&c_src_path)
+                .context("Failed to open C source code file")?;
+            c_src_file.write_all(WASMER_MAIN_C_SOURCE)?;
+        }
+        run_c_compile(c_src_path, &c_src_obj, self.target_triple.clone())
+            .context("Failed to compile C source code")?;
+        LinkCode {
+            object_paths: vec![c_src_obj, wasm_object_path],
+            output_path,
+            additional_libraries: self.libraries.clone(),
+            target: self.target_triple.clone(),
+            ..Default::default()
+        }
+        .run()
+        .context("Failed to link objects together")?;
+
+        Ok(())
+    }
+}
+
+fn get_wasmer_dir() -> anyhow::Result<PathBuf> {
+    Ok(PathBuf::from(
+        env::var("WASMER_DIR")
+            .or_else(|e| {
+                option_env!("WASMER_INSTALL_PREFIX")
+                    .map(str::to_string)
+                    .ok_or(e)
+            })
+            .context("Trying to read env var `WASMER_DIR`")?,
+    ))
+}
+
+fn get_wasmer_include_directory() -> anyhow::Result<PathBuf> {
+    let mut path = get_wasmer_dir()?;
+    path.push("include");
+    Ok(path)
+}
+
+/// path to the static libwasmer
+fn get_libwasmer_path() -> anyhow::Result<PathBuf> {
+    let mut path = get_wasmer_dir()?;
+    path.push("lib");
+
+    // TODO: prefer headless Wasmer if/when it's a separate library.
+    #[cfg(not(windows))]
+    path.push("libwasmer.a");
+    #[cfg(windows)]
+    path.push("wasmer.lib");
+
+    Ok(path)
+}
+
+/// Compile the C code.
+fn run_c_compile(
+    path_to_c_src: &Path,
+    output_name: &Path,
+    target: Option<Triple>,
+) -> anyhow::Result<()> {
+    #[cfg(not(windows))]
+    let c_compiler = "cc";
+    // We must use a C++ compiler on Windows because wasm.h uses `static_assert`
+    // which isn't available in `clang` on Windows.
+    #[cfg(windows)]
+    let c_compiler = "clang++";
+
+    let mut command = Command::new(c_compiler);
+    let command = command
+        .arg("-O2")
+        .arg("-c")
+        .arg(path_to_c_src)
+        .arg("-I")
+        .arg(get_wasmer_include_directory()?);
+
+    let command = if let Some(target) = target {
+        command.arg("-target").arg(format!("{}", target))
+    } else {
+        command
+    };
+
+    let output = command.arg("-o").arg(output_name).output()?;
+
+    if !output.status.success() {
+        bail!(
+            "C code compile failed with: stdout: {}\n\nstderr: {}",
+            std::str::from_utf8(&output.stdout)
+                .expect("stdout is not utf8! need to handle arbitrary bytes"),
+            std::str::from_utf8(&output.stderr)
+                .expect("stderr is not utf8! need to handle arbitrary bytes")
+        );
+    }
+    Ok(())
+}
+
+/// Data used to run a linking command for generated artifacts.
+#[derive(Debug)]
+struct LinkCode {
+    /// Path to the linker used to run the linking command.
+    linker_path: PathBuf,
+    /// String used as an optimization flag.
+    optimization_flag: String,
+    /// Paths of objects to link.
+    object_paths: Vec<PathBuf>,
+    /// Additional libraries to link against.
+    additional_libraries: Vec<String>,
+    /// Path to the output target.
+    output_path: PathBuf,
+    /// Path to the dir containing the static libwasmer library.
+    libwasmer_path: PathBuf,
+    /// The target to link the executable for.
+    target: Option<Triple>,
+}
+
+impl Default for LinkCode {
+    fn default() -> Self {
+        #[cfg(not(windows))]
+        let linker = "cc";
+        #[cfg(windows)]
+        let linker = "clang";
+        Self {
+            linker_path: PathBuf::from(linker),
+            optimization_flag: String::from("-O2"),
+            object_paths: vec![],
+            additional_libraries: vec![],
+            output_path: PathBuf::from("a.out"),
+            libwasmer_path: get_libwasmer_path().unwrap(),
+            target: None,
+        }
+    }
+}
+
+impl LinkCode {
+    fn run(&self) -> anyhow::Result<()> {
+        let mut command = Command::new(&self.linker_path);
+        let command = command
+            .arg(&self.optimization_flag)
+            .args(
+                self.object_paths
+                    .iter()
+                    .map(|path| path.canonicalize().unwrap()),
+            )
+            .arg(
+                &self
+                    .libwasmer_path
+                    .canonicalize()
+                    .context("Failed to find libwasmer")?,
+            );
+        let command = if let Some(target) = &self.target {
+            command.arg("-target").arg(format!("{}", target))
+        } else {
+            command
+        };
+        // Add libraries required per platform.
+        // We need userenv, sockets (Ws2_32), advapi32 for some system calls and bcrypt for random numbers.
+        #[cfg(windows)]
+        let command = command
+            .arg("-luserenv")
+            .arg("-lWs2_32")
+            .arg("-ladvapi32")
+            .arg("-lbcrypt");
+        // On unix we need dlopen-related symbols, libmath for a few things, and pthreads.
+        #[cfg(not(windows))]
+        let command = command.arg("-ldl").arg("-lm").arg("-pthread");
+        let link_aganist_extra_libs = self
+            .additional_libraries
+            .iter()
+            .map(|lib| format!("-l{}", lib));
+        let command = command.args(link_aganist_extra_libs);
+        let output = command.arg("-o").arg(&self.output_path).output()?;
+
+        if !output.status.success() {
+            bail!(
+                "linking failed with: stdout: {}\n\nstderr: {}",
+                std::str::from_utf8(&output.stdout)
+                    .expect("stdout is not utf8! need to handle arbitrary bytes"),
+                std::str::from_utf8(&output.stderr)
+                    .expect("stderr is not utf8! need to handle arbitrary bytes")
+            );
+        }
+        Ok(())
+    }
+}