3 files changed, 256 insertions, 0 deletions
diff --git a/misc/reboot/experiment_toolid_test.go b/misc/reboot/experiment_toolid_test.go
new file mode 100644
index 0000000..87a828e
--- /dev/null
+++ b/misc/reboot/experiment_toolid_test.go
@@ -0,0 +1,101 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build explicit
+// +build explicit
+
+// Package experiment_toolid_test verifies that GOEXPERIMENT settings built
+// into the toolchain influence tool ids in the Go command.
+// This test requires bootstrapping the toolchain twice, so it's very expensive.
+// It must be run explicitly with -tags=explicit.
+// Verifies golang.org/issue/33091.
+package reboot_test
+
+import (
+	"bytes"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+func TestExperimentToolID(t *testing.T) {
+	// Set up GOROOT
+	goroot, err := os.MkdirTemp("", "experiment-goroot")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(goroot)
+
+	gorootSrc := filepath.Join(goroot, "src")
+	if err := overlayDir(gorootSrc, filepath.Join(runtime.GOROOT(), "src")); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := os.WriteFile(filepath.Join(goroot, "VERSION"), []byte("go1.999"), 0666); err != nil {
+		t.Fatal(err)
+	}
+	env := append(os.Environ(), "GOROOT=", "GOROOT_BOOTSTRAP="+runtime.GOROOT())
+
+	// Use a clean cache.
+	gocache, err := os.MkdirTemp("", "experiment-gocache")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(gocache)
+	env = append(env, "GOCACHE="+gocache)
+
+	// Build the toolchain without GOEXPERIMENT.
+	var makeScript string
+	switch runtime.GOOS {
+	case "windows":
+		makeScript = "make.bat"
+	case "plan9":
+		makeScript = "make.rc"
+	default:
+		makeScript = "make.bash"
+	}
+	makeScriptPath := filepath.Join(runtime.GOROOT(), "src", makeScript)
+	runCmd(t, gorootSrc, env, makeScriptPath)
+
+	// Verify compiler version string.
+	goCmdPath := filepath.Join(goroot, "bin", "go")
+	if runtime.GOOS == "windows" {
+		goCmdPath += ".exe"
+	}
+	gotVersion := bytes.TrimSpace(runCmd(t, gorootSrc, env, goCmdPath, "tool", "compile", "-V=full"))
+	wantVersion := []byte(`compile version go1.999`)
+	if !bytes.Equal(gotVersion, wantVersion) {
+		t.Errorf("compile version without experiment: got %q, want %q", gotVersion, wantVersion)
+	}
+
+	// Build a package in a mode not handled by the make script.
+	runCmd(t, gorootSrc, env, goCmdPath, "build", "-race", "archive/tar")
+
+	// Rebuild the toolchain with GOEXPERIMENT.
+	env = append(env, "GOEXPERIMENT=fieldtrack")
+	runCmd(t, gorootSrc, env, makeScriptPath)
+
+	// Verify compiler version string.
+	gotVersion = bytes.TrimSpace(runCmd(t, gorootSrc, env, goCmdPath, "tool", "compile", "-V=full"))
+	wantVersion = []byte(`compile version go1.999 X:fieldtrack,framepointer`)
+	if !bytes.Equal(gotVersion, wantVersion) {
+		t.Errorf("compile version with experiment: got %q, want %q", gotVersion, wantVersion)
+	}
+
+	// Build the same package. We should not get a cache conflict.
+	runCmd(t, gorootSrc, env, goCmdPath, "build", "-race", "archive/tar")
+}
+
+func runCmd(t *testing.T, dir string, env []string, path string, args ...string) []byte {
+	cmd := exec.Command(path, args...)
+	cmd.Dir = dir
+	cmd.Env = env
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return out
+}
diff --git a/misc/reboot/overlaydir_test.go b/misc/reboot/overlaydir_test.go
new file mode 100644
index 0000000..71faf09
--- /dev/null
+++ b/misc/reboot/overlaydir_test.go
@@ -0,0 +1,85 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package reboot_test
+
+import (
+	"io"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// overlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
+//
+// TODO: Once we no longer need to support the misc module in GOPATH mode,
+// factor this function out into a package to reduce duplication.
+func overlayDir(dstRoot, srcRoot string) error {
+	dstRoot = filepath.Clean(dstRoot)
+	if err := os.MkdirAll(dstRoot, 0777); err != nil {
+		return err
+	}
+
+	srcRoot, err := filepath.Abs(srcRoot)
+	if err != nil {
+		return err
+	}
+
+	return filepath.WalkDir(srcRoot, func(srcPath string, entry fs.DirEntry, err error) error {
+		if err != nil || srcPath == srcRoot {
+			return err
+		}
+		if filepath.Base(srcPath) == "testdata" {
+			// We're just building, so no need to copy those.
+			return fs.SkipDir
+		}
+
+		suffix := strings.TrimPrefix(srcPath, srcRoot)
+		for len(suffix) > 0 && suffix[0] == filepath.Separator {
+			suffix = suffix[1:]
+		}
+		dstPath := filepath.Join(dstRoot, suffix)
+
+		info, err := entry.Info()
+		perm := info.Mode() & os.ModePerm
+		if info.Mode()&os.ModeSymlink != 0 {
+			info, err = os.Stat(srcPath)
+			if err != nil {
+				return err
+			}
+			perm = info.Mode() & os.ModePerm
+		}
+
+		// Always make copies of directories.
+		// If we add a file in the overlay, we don't want to add it in the original.
+		if info.IsDir() {
+			return os.MkdirAll(dstPath, perm|0200)
+		}
+
+		// If we can use a hard link, do that instead of copying bytes.
+		// Go builds don't like symlinks in some cases, such as go:embed.
+		if err := os.Link(srcPath, dstPath); err == nil {
+			return nil
+		}
+
+		// Otherwise, copy the bytes.
+		src, err := os.Open(srcPath)
+		if err != nil {
+			return err
+		}
+		defer src.Close()
+
+		dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
+		if err != nil {
+			return err
+		}
+
+		_, err = io.Copy(dst, src)
+		if closeErr := dst.Close(); err == nil {
+			err = closeErr
+		}
+		return err
+	})
+}
diff --git a/misc/reboot/reboot_test.go b/misc/reboot/reboot_test.go
new file mode 100644
index 0000000..a1b513b
--- /dev/null
+++ b/misc/reboot/reboot_test.go
@@ -0,0 +1,70 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package reboot_test verifies that the current GOROOT can be used to bootstrap
+// itself.
+package reboot_test
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func TestRepeatBootstrap(t *testing.T) {
+	if testing.Short() {
+		t.Skipf("skipping test that rebuilds the entire toolchain")
+	}
+
+	realGoroot, err := filepath.Abs(filepath.Join("..", ".."))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// To ensure that bootstrapping doesn't unexpectedly depend
+	// on the Go repo's git metadata, add a fake (unreadable) git
+	// directory above the simulated GOROOT.
+	// This mimics the configuration one much have when
+	// building from distro-packaged source code
+	// (see https://go.dev/issue/54852).
+	parent := t.TempDir()
+	dotGit := filepath.Join(parent, ".git")
+	if err := os.Mkdir(dotGit, 000); err != nil {
+		t.Fatal(err)
+	}
+	goroot := filepath.Join(parent, "goroot")
+
+	gorootSrc := filepath.Join(goroot, "src")
+	overlayStart := time.Now()
+	if err := overlayDir(gorootSrc, filepath.Join(realGoroot, "src")); err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("GOROOT/src overlay set up in %s", time.Since(overlayStart))
+
+	if err := os.WriteFile(filepath.Join(goroot, "VERSION"), []byte(runtime.Version()), 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	var makeScript string
+	switch runtime.GOOS {
+	case "windows":
+		makeScript = "make.bat"
+	case "plan9":
+		makeScript = "make.rc"
+	default:
+		makeScript = "make.bash"
+	}
+
+	cmd := exec.Command(filepath.Join(goroot, "src", makeScript))
+	cmd.Dir = gorootSrc
+	cmd.Env = append(cmd.Environ(), "GOROOT=", "GOROOT_BOOTSTRAP="+realGoroot)
+	cmd.Stderr = os.Stderr
+	cmd.Stdout = os.Stdout
+	if err := cmd.Run(); err != nil {
+		t.Fatal(err)
+	}
+}