ldd: cancel on decoder error

This prevents blocking from failures caused by ldd(1) emitting output that is not anticipated by the decoder.

Signed-off-by: Ophestra <cat@gensokyo.uk>

ldd/exec.go

@@ -68,6 +68,11 @@ func Exec(ctx context.Context, msg message.Msg, p string) ([]*Entry, error) {
 	}
 
 	entries, decodeErr := d.Decode()
+	if decodeErr != nil {
+		// do not cancel on successful decode to avoid racing with ldd(1) termination
+		cancel()
+	}
+
 	if err := z.Wait(); err != nil {
 		m := stderr.Bytes()
 		if bytes.Contains(m, []byte(msgStaticSuffix)) || bytes.Contains(m, []byte(msgStaticGlibc)) {

ldd/exec_test.go

@@ -0,0 +1,45 @@
+package ldd_test
+
+import (
+	"errors"
+	"os"
+	"os/exec"
+	"testing"
+
+	"hakurei.app/container"
+	"hakurei.app/ldd"
+	"hakurei.app/message"
+)
+
+func TestExec(t *testing.T) {
+	t.Parallel()
+
+	t.Run("failure", func(t *testing.T) {
+		t.Parallel()
+
+		_, err := ldd.Exec(t.Context(), nil, "/proc/nonexistent")
+
+		var exitError *exec.ExitError
+		if !errors.As(err, &exitError) {
+			t.Fatalf("Exec: error has incorrect concrete type: %#v", err)
+		}
+
+		const want = 1
+		if got := exitError.ExitCode(); got != want {
+			t.Fatalf("Exec: ExitCode = %d, want %d", got, want)
+		}
+	})
+
+	t.Run("success", func(t *testing.T) {
+		msg := message.New(nil)
+		msg.GetLogger().SetPrefix("check: ")
+		if entries, err := ldd.Exec(t.Context(), nil, container.MustExecutable(msg)); err != nil {
+			t.Fatalf("Exec: error = %v", err)
+		} else if testing.Verbose() {
+			// result cannot be measured here as build information is not known
+			t.Logf("Exec: %q", entries)
+		}
+	})
+}
+
+func TestMain(m *testing.M) { container.TryArgv0(nil); os.Exit(m.Run()) }