diff --git a/README.md b/README.md
index d28db110..56593341 100644
--- a/README.md
+++ b/README.md
@@ -176,8 +176,8 @@ Here are some examples related to Go syntax:
 
 * [concat](_demo/concat/concat.go): define a variadic function
 * [genints](_demo/genints/genints.go): various forms of closure usage (including C function, recv.method and anonymous function)
-* [errors](_demo/errors/errors.go): demo to implement error interface
-* [defer](_demo/defer/defer.go): defer demo
+* [errors](_cmptest/errors/errors.go): demo to implement error interface
+* [defer](_cmptest/defer/defer.go): defer demo
 * [goroutine](_demo/goroutine/goroutine.go): goroutine demo
 
 
diff --git a/_demo/defer/defer.go b/_cmptest/defer/defer.go
similarity index 100%
rename from _demo/defer/defer.go
rename to _cmptest/defer/defer.go
diff --git a/_demo/errors/errors.go b/_cmptest/errors/errors.go
similarity index 96%
rename from _demo/errors/errors.go
rename to _cmptest/errors/errors.go
index 4e73a70c..4c4080d5 100644
--- a/_demo/errors/errors.go
+++ b/_cmptest/errors/errors.go
@@ -17,6 +17,5 @@ func (e *errorString) Error() string {
 
 func main() {
 	err := New("an error")
-	println(err)
 	println(err.Error())
 }
diff --git a/_demo/genints/gen_ints.go b/_demo/genints/genints.go
similarity index 100%
rename from _demo/genints/gen_ints.go
rename to _demo/genints/genints.go
diff --git a/cmd/internal/run/run.go b/cmd/internal/run/run.go
index 8c0a9fe1..4d314cde 100644
--- a/cmd/internal/run/run.go
+++ b/cmd/internal/run/run.go
@@ -35,14 +35,29 @@ var Cmd = &base.Command{
 	Short:     "Compile and run Go program",
 }
 
+// llgo cmptest
+var CmpTestCmd = &base.Command{
+	UsageLine: "llgo cmptest [build flags] package [arguments...]",
+	Short:     "Compile programs by llgo and go, run them and do comparative tests (stdout/stderr/exitcode)",
+}
+
 func init() {
 	Cmd.Run = runCmd
+	CmpTestCmd.Run = runCmpTest
 }
 
 func runCmd(cmd *base.Command, args []string) {
+	runCmdEx(cmd, args, build.ModeRun)
+}
+
+func runCmpTest(cmd *base.Command, args []string) {
+	runCmdEx(cmd, args, build.ModeCmpTest)
+}
+
+func runCmdEx(cmd *base.Command, args []string, mode build.Mode) {
 	args, runArgs, err := parseRunArgs(args)
 	check(err)
-	conf := build.NewDefaultConf(build.ModeRun)
+	conf := build.NewDefaultConf(mode)
 	conf.RunArgs = runArgs
 	build.Do(args, conf)
 }
diff --git a/cmd/llgo/llgo.go b/cmd/llgo/llgo.go
index 85304dd1..69c4444d 100644
--- a/cmd/llgo/llgo.go
+++ b/cmd/llgo/llgo.go
@@ -43,6 +43,7 @@ func init() {
 		build.Cmd,
 		install.Cmd,
 		run.Cmd,
+		run.CmpTestCmd,
 		clean.Cmd,
 	}
 }
diff --git a/internal/build/build.go b/internal/build/build.go
index 7fdc440e..de0b52c0 100644
--- a/internal/build/build.go
+++ b/internal/build/build.go
@@ -50,6 +50,7 @@ const (
 	ModeBuild Mode = iota
 	ModeInstall
 	ModeRun
+	ModeCmpTest
 )
 
 const (
@@ -380,7 +381,8 @@ func linkMainPkg(pkg *packages.Package, pkgs []*aPackage, llFiles []string, conf
 	err := clang.New("").Exec(args...)
 	check(err)
 
-	if mode == ModeRun {
+	switch mode {
+	case ModeRun:
 		cmd := exec.Command(app, conf.RunArgs...)
 		cmd.Stdin = os.Stdin
 		cmd.Stdout = os.Stdout
@@ -389,6 +391,8 @@ func linkMainPkg(pkg *packages.Package, pkgs []*aPackage, llFiles []string, conf
 		if s := cmd.ProcessState; s != nil {
 			os.Exit(s.ExitCode())
 		}
+	case ModeCmpTest:
+		cmpTest("", pkgPath, app, conf.RunArgs)
 	}
 	return
 }
@@ -687,38 +691,6 @@ func isPkgInMod(pkgPath, modPath string) bool {
 	return false
 }
 
-/*
-func llgoPkgLinkFile(pkgPath string) string {
-	// if kind == cl.PkgLinkBitCode {
-	//	return filepath.Join(llgoRoot()+pkgPath[len(llgoModPath):], "llgo_autogen.bc")
-	// }
-	llFile := filepath.Join(llgoRoot()+pkgPath[len(llgoModPath):], "llgo_autogen.ll")
-	if _, err := os.Stat(llFile); os.IsNotExist(err) {
-		decodeLinkFile(llFile)
-	}
-	return llFile
-}
-
-// *.ll => *.lla
-func decodeLinkFile(llFile string) {
-	zipFile := llFile + "a"
-	zipf, err := zip.OpenReader(zipFile)
-	if err != nil {
-		return
-	}
-	defer zipf.Close()
-	f, err := zipf.Open("llgo_autogen.ll")
-	if err != nil {
-		return
-	}
-	defer f.Close()
-	data, err := io.ReadAll(f)
-	if err == nil {
-		os.WriteFile(llFile, data, 0644)
-	}
-}
-*/
-
 func decodeFile(outFile string, zipf *zip.File) (err error) {
 	f, err := zipf.Open()
 	if err != nil {
diff --git a/internal/build/cmptest.go b/internal/build/cmptest.go
new file mode 100644
index 00000000..d7b8a521
--- /dev/null
+++ b/internal/build/cmptest.go
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package build
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+)
+
+func cmpTest(dir, pkgPath, llApp string, runArgs []string) {
+	var goOut, goErr bytes.Buffer
+	var llgoOut, llgoErr bytes.Buffer
+	var llgoRunErr = runApp(runArgs, dir, &llgoOut, &llgoErr, llApp)
+	var goRunErr = runApp(runArgs, dir, &goOut, &goErr, "go", "run", pkgPath)
+	checkEqual("output", llgoOut.Bytes(), goOut.Bytes())
+	checkEqual("stderr", llgoErr.Bytes(), goErr.Bytes())
+	checkEqualRunErr(llgoRunErr, goRunErr)
+}
+
+func checkEqualRunErr(llgoRunErr, goRunErr error) {
+	if llgoRunErr == goRunErr {
+		return
+	}
+	fmt.Fprintln(os.Stderr, "=> Exit:", llgoRunErr)
+	fmt.Fprintln(os.Stderr, "\n=> Expected Exit:", goRunErr)
+}
+
+func checkEqual(prompt string, a, expected []byte) {
+	if bytes.Equal(a, expected) {
+		return
+	}
+
+	fmt.Fprintln(os.Stderr, "=> Result of", prompt)
+	os.Stderr.Write(a)
+
+	fmt.Fprintln(os.Stderr, "\n=> Expected", prompt)
+	os.Stderr.Write(expected)
+
+	fatal(errors.New("checkEqual: unexpected " + prompt))
+}
+
+func runApp(runArgs []string, dir string, stdout, stderr io.Writer, app string, args ...string) error {
+	if len(runArgs) > 0 {
+		if len(args) > 0 {
+			args = append(args, runArgs...)
+		} else {
+			args = runArgs
+		}
+	}
+	cmd := exec.Command(app, args...)
+	cmd.Dir = dir
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
+	return cmd.Run()
+}
+
+func fatal(err error) {
+	log.Panicln(err)
+}
diff --git a/internal/runtime/z_print.go b/internal/runtime/z_print.go
index 6c426edc..85c09b70 100644
--- a/internal/runtime/z_print.go
+++ b/internal/runtime/z_print.go
@@ -22,16 +22,19 @@ import (
 	"github.com/goplus/llgo/c"
 )
 
-func PrintByte(v byte) {
-	c.Fputc(c.Int(v), c.Stderr)
+func boolCStr(v bool) *c.Char {
+	if v {
+		return c.Str("true")
+	}
+	return c.Str("false")
 }
 
 func PrintBool(v bool) {
-	if v {
-		c.Fprintf(c.Stderr, c.Str("true"))
-	} else {
-		c.Fprintf(c.Stderr, c.Str("false"))
-	}
+	c.Fprintf(c.Stderr, boolCStr(v))
+}
+
+func PrintByte(v byte) {
+	c.Fputc(c.Int(v), c.Stderr)
 }
 
 func PrintFloat(v float64) {