1 files changed, 95 insertions, 7 deletions
diff --git a/src/cmd/pack/pack_test.go b/src/cmd/pack/pack_test.go
index 9f65705def..118376f9df 100644
--- a/src/cmd/pack/pack_test.go
+++ b/src/cmd/pack/pack_test.go
@@ -12,7 +12,6 @@ import (
 	"internal/testenv"
 	"io"
 	"io/fs"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -22,7 +21,7 @@ import (
 
 // tmpDir creates a temporary directory and returns its name.
 func tmpDir(t *testing.T) string {
-	name, err := ioutil.TempDir("", "pack")
+	name, err := os.MkdirTemp("", "pack")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -158,7 +157,7 @@ func TestExtract(t *testing.T) {
 	ar = openArchive(name, os.O_RDONLY, []string{goodbyeFile.name})
 	ar.scan(ar.extractContents)
 	ar.a.File().Close()
-	data, err := ioutil.ReadFile(goodbyeFile.name)
+	data, err := os.ReadFile(goodbyeFile.name)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -183,7 +182,7 @@ func TestHello(t *testing.T) {
 			println("hello world")
 		}
 	`
-	err := ioutil.WriteFile(hello, []byte(prog), 0666)
+	err := os.WriteFile(hello, []byte(prog), 0666)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -251,7 +250,7 @@ func TestLargeDefs(t *testing.T) {
 			println("ok")
 		}
 	`
-	err = ioutil.WriteFile(main, []byte(prog), 0666)
+	err = os.WriteFile(main, []byte(prog), 0666)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -281,13 +280,13 @@ func TestIssue21703(t *testing.T) {
 	defer os.RemoveAll(dir)
 
 	const aSrc = `package a; const X = "\n!\n"`
-	err := ioutil.WriteFile(filepath.Join(dir, "a.go"), []byte(aSrc), 0666)
+	err := os.WriteFile(filepath.Join(dir, "a.go"), []byte(aSrc), 0666)
 	if err != nil {
 		t.Fatal(err)
 	}
 
 	const bSrc = `package b; import _ "a"`
-	err = ioutil.WriteFile(filepath.Join(dir, "b.go"), []byte(bSrc), 0666)
+	err = os.WriteFile(filepath.Join(dir, "b.go"), []byte(bSrc), 0666)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -303,6 +302,95 @@ func TestIssue21703(t *testing.T) {
 	run(goBin, "tool", "compile", "-I", ".", "b.go")
 }
 
+// Test the "c" command can "see through" the archive generated by the compiler.
+// This is peculiar. (See issue #43271)
+func TestCreateWithCompilerObj(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+
+	dir := tmpDir(t)
+	defer os.RemoveAll(dir)
+	src := filepath.Join(dir, "p.go")
+	prog := "package p; var X = 42\n"
+	err := os.WriteFile(src, []byte(prog), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	run := func(args ...string) string {
+		return doRun(t, dir, args...)
+	}
+
+	goBin := testenv.GoToolPath(t)
+	run(goBin, "build", "cmd/pack") // writes pack binary to dir
+	run(goBin, "tool", "compile", "-pack", "-o", "p.a", "p.go")
+	run("./pack", "c", "packed.a", "p.a")
+	fi, err := os.Stat(filepath.Join(dir, "p.a"))
+	if err != nil {
+		t.Fatalf("stat p.a failed: %v", err)
+	}
+	fi2, err := os.Stat(filepath.Join(dir, "packed.a"))
+	if err != nil {
+		t.Fatalf("stat packed.a failed: %v", err)
+	}
+	// For compiler-generated object file, the "c" command is
+	// expected to get (essentially) the same file back, instead
+	// of packing it into a new archive with a single entry.
+	if want, got := fi.Size(), fi2.Size(); want != got {
+		t.Errorf("packed file with different size: want %d, got %d", want, got)
+	}
+
+	// Test -linkobj flag as well.
+	run(goBin, "tool", "compile", "-linkobj", "p2.a", "-o", "p.x", "p.go")
+	run("./pack", "c", "packed2.a", "p2.a")
+	fi, err = os.Stat(filepath.Join(dir, "p2.a"))
+	if err != nil {
+		t.Fatalf("stat p2.a failed: %v", err)
+	}
+	fi2, err = os.Stat(filepath.Join(dir, "packed2.a"))
+	if err != nil {
+		t.Fatalf("stat packed2.a failed: %v", err)
+	}
+	if want, got := fi.Size(), fi2.Size(); want != got {
+		t.Errorf("packed file with different size: want %d, got %d", want, got)
+	}
+
+	run("./pack", "c", "packed3.a", "p.x")
+	fi, err = os.Stat(filepath.Join(dir, "p.x"))
+	if err != nil {
+		t.Fatalf("stat p.x failed: %v", err)
+	}
+	fi2, err = os.Stat(filepath.Join(dir, "packed3.a"))
+	if err != nil {
+		t.Fatalf("stat packed3.a failed: %v", err)
+	}
+	if want, got := fi.Size(), fi2.Size(); want != got {
+		t.Errorf("packed file with different size: want %d, got %d", want, got)
+	}
+}
+
+// Test the "r" command creates the output file if it does not exist.
+func TestRWithNonexistentFile(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+
+	dir := tmpDir(t)
+	defer os.RemoveAll(dir)
+	src := filepath.Join(dir, "p.go")
+	prog := "package p; var X = 42\n"
+	err := os.WriteFile(src, []byte(prog), 0666)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	run := func(args ...string) string {
+		return doRun(t, dir, args...)
+	}
+
+	goBin := testenv.GoToolPath(t)
+	run(goBin, "build", "cmd/pack") // writes pack binary to dir
+	run(goBin, "tool", "compile", "-o", "p.o", "p.go")
+	run("./pack", "r", "p.a", "p.o") // should succeed
+}
+
 // doRun runs a program in a directory and returns the output.
 func doRun(t *testing.T, dir string, args ...string) string {
 	cmd := exec.Command(args[0], args[1:]...)