fix(go-runner): detect missing C compiler before building instrument hooks

Author: not-matthias

go-runner/src/runner/mod.rs

@@ -8,17 +8,43 @@ use tempfile::TempDir;
 
 mod overlay;
 
+fn check_c_compiler(go_binary: &Path) -> anyhow::Result<()> {
+    let output = Command::new(go_binary)
+        .args(["env", "CC"])
+        .output()
+        .context("Failed to run `go env CC`")?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        bail!("Failed to determine C compiler via `go env CC`: {stderr}");
+    }
+
+    let cc = String::from_utf8_lossy(&output.stdout).trim().to_string();
+    if cc.is_empty() {
+        bail!(
+            "No C compiler found. The CodSpeed Go runner requires a C compiler (gcc/cc) \
+             to build the instrumentation hooks. Install `build-essential` on Ubuntu/Debian \
+             or the equivalent for your platform."
+        );
+    }
+
+    Ok(())
+}
+
 fn run_cmd<P: AsRef<Path>>(
     profile_dir: P,
     dir: P,
     cli: &Cli,
 ) -> anyhow::Result<(TempDir, Command)> {
-    let (_dir, overlay_file) = overlay::get_overlay_file(profile_dir.as_ref())?;
-
     // Execute the `go test` command using the go binary, rather than the one in the PATH
     // to avoid running into infinite loops with the runner which tries to intercept `go test`.
     let go_binary = find_go_binary()?;
 
+    // Check early, before downloading instrument-hooks and generating the overlay.
+    check_c_compiler(&go_binary)?;
+
+    let (_dir, overlay_file) = overlay::get_overlay_file(profile_dir.as_ref())?;
+
     // Convert the CLI struct into a command:
     let mut cmd = Command::new(go_binary);
     cmd.args([
@@ -44,6 +70,11 @@ fn run_cmd<P: AsRef<Path>>(
     cmd.env("GOCACHE", _dir.path().join("gocache"));
     cmd.env("GOMODCACHE", _dir.path().join("gomodcache"));
 
+    // The overlay includes instrument-hooks.go which uses cgo (`import "C"`).
+    // If CGO_ENABLED=0 (e.g. no C compiler on a bare metal runner), Go silently
+    // excludes the file, causing "undefined: InstrumentHooks" build errors.
+    cmd.env("CGO_ENABLED", "1");
+
     Ok((_dir, cmd))
 }