automatically find C compiler and let user set one

src/cc.rs

@@ -1,6 +1,40 @@
-use std::{io, path::Path, process::Command};
+use std::{
+    io,
+    path::Path,
+    process::{Command, ExitStatus, Output},
+};
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    /// no compiler specified, all defaults failed
+    #[error("couldn't find a C compiler")]
+    NoCompiler,
+
+    /// user specified a compiler and it didn't work
+    #[error("couldn't execute `{cmd}`: {src}")]
+    BadCompiler { cmd: String, src: io::Error },
+
+    /// user specified a compiler and it's nonsense
+    #[error("compiler can't be empty")]
+    EmptyCompiler,
+
+    /// compiler ran but failed for some reason
+    #[error("compiler failed with {status}\n\n{}", String::from_utf8_lossy(.stderr))]
+    ExecFailed { status: ExitStatus, stderr: Vec<u8> },
+}
+
+fn to_res(Output { status, stderr, .. }: Output) -> Result<(), Error> {
+    status
+        .success()
+        .then_some(())
+        .ok_or(Error::ExecFailed { status, stderr })
+}
+
+// there's probably a platform dependent better order for searching these. too bad !
+const DEFAULT_COMPILERS: [&str; 3] = ["cc", "gcc", "clang"];
 
 pub struct Build<'a> {
+    compiler: Option<&'a str>,
     dir: Option<&'a Path>,
     inputs: Vec<&'a str>,
 }
@@ -8,30 +42,41 @@ pub struct Build<'a> {
 impl<'a> Build<'a> {
     pub fn new() -> Self {
         Self {
+            compiler: None,
             dir: None,
             inputs: Vec::new(),
         }
     }
 
-    pub fn compile(self, output_path: &Path) -> io::Result<()> {
-        let mut cmd = Command::new("cc");
+    pub fn compile(self, output_path: &Path) -> Result<(), Error> {
+        if let Some(compiler) = self.compiler {
+            let mut parts = compiler.split_whitespace();
+            let mut cmd = Command::new(parts.next().ok_or(Error::EmptyCompiler)?);
+            cmd.args(parts);
 
-        cmd.arg("-fpic").arg("-shared").arg("-std=c11");
-
-        if let Some(path) = self.dir {
-            cmd.current_dir(path);
+            return match self.try_compile(cmd, output_path) {
+                Err(e) => Err(Error::BadCompiler {
+                    cmd: compiler.to_owned(),
+                    src: e,
+                }),
+                Ok(output) => to_res(output),
+            };
         }
 
-        cmd.args(&self.inputs);
-        cmd.arg("-o").arg(output_path);
+        for cc in DEFAULT_COMPILERS {
+            let cmd = Command::new(cc);
 
-        dbg!(&cmd);
+            if let Ok(output) = self.try_compile(cmd, output_path) {
+                return to_res(output);
+            }
+        }
 
-        let mut child = cmd.spawn()?;
+        Err(Error::NoCompiler)
+    }
 
-        let _ = child.wait();
-
-        Ok(())
+    pub fn compiler(&mut self, compiler: Option<&'a str>) -> &mut Self {
+        self.compiler = compiler;
+        self
     }
 
     pub fn dir(&mut self, path: &'a Path) -> &mut Self {
@@ -45,4 +90,17 @@ impl<'a> Build<'a> {
         }
         self
     }
+
+    fn try_compile(&self, mut cmd: Command, output_path: &Path) -> io::Result<Output> {
+        cmd.arg("-fpic").arg("-shared").arg("-std=c11");
+
+        if let Some(path) = self.dir {
+            cmd.current_dir(path);
+        }
+
+        cmd.args(&self.inputs);
+        cmd.arg("-o").arg(output_path);
+
+        cmd.output()
+    }
 }

src/main.rs

@@ -19,7 +19,10 @@ struct Cli {
 fn main() -> anyhow::Result<()> {
     let Cli { language } = Cli::parse();
 
-    let Settings { parser_dir } = get_settings()?;
+    let Settings {
+        parser_dir,
+        compiler,
+    } = get_settings()?;
 
     let src_dir = tempfile::tempdir()?;
 
@@ -37,7 +40,10 @@ fn main() -> anyhow::Result<()> {
     let output_path = parser_dir.join(language).with_extension(DLL_EXTENSION);
 
     let mut build = cc::Build::new();
-    build.dir(&repo_path).input_files(files);
+    build
+        .compiler(compiler.as_deref())
+        .dir(&repo_path)
+        .input_files(files);
     build.compile(&output_path)?;
 
     // close explicitly to prevent premature drop

src/settings.rs

@@ -13,6 +13,9 @@ lazy_static! {
 pub struct Settings {
     #[serde(default = "default_parser_dir")]
     pub parser_dir: PathBuf,
+
+    #[serde(alias = "cc")]
+    pub compiler: Option<String>,
 }
 
 fn default_parser_dir() -> PathBuf {