cmd/go: remove work directory on usage error

Backport https://golang.org/cl/163237 from the master library:
    
        Ensure that cmd/go consistently calls base.Exit rather than os.Exit,
        so that we don't incorrectly leave the work directory around on exit.
    
        Test this by modifying the testsuite to run all the tests with TMPDIR
        set to a temporary directory, and then check that no files are left
        behind in that temporary directory. Adjust a couple of tests to make
        this approach work.
    
    Updates https://gcc.gnu.org/PR89406
    
    Reviewed-on: https://go-review.googlesource.com/c/163198

From-SVN: r269086

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-43e458ab704e04cdf347f3e74e0b0eff3de00a3d
+4fbd06dc7b1b8fb665293399a2b6d5326435512f
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/cmd/go/go_test.go

@@ -146,7 +146,18 @@ func TestMain(m *testing.M) {
 		select {}
 	}
 
-	dir, err := ioutil.TempDir(os.Getenv("GOTMPDIR"), "cmd-go-test-")
+	// Run with a temporary TMPDIR to check that the tests don't
+	// leave anything behind.
+	topTmpdir, err := ioutil.TempDir("", "cmd-go-test-")
+	if err != nil {
+		log.Fatal(err)
+	}
+	if !*testWork {
+		defer removeAll(topTmpdir)
+	}
+	os.Setenv(tempEnvName(), topTmpdir)
+
+	dir, err := ioutil.TempDir(topTmpdir, "tmpdir")
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -258,6 +269,23 @@ func TestMain(m *testing.M) {
 		removeAll(testTmpDir) // os.Exit won't run defer
 	}
 
+	if !*testWork {
+		// There shouldn't be anything left in topTmpdir.
+		dirf, err := os.Open(topTmpdir)
+		if err != nil {
+			log.Fatal(err)
+		}
+		names, err := dirf.Readdirnames(0)
+		if err != nil {
+			log.Fatal(err)
+		}
+		if len(names) > 0 {
+			log.Fatalf("unexpected files left in tmpdir: %v", names)
+		}
+
+		removeAll(topTmpdir)
+	}
+
 	os.Exit(r)
 }
 
@@ -5020,7 +5048,8 @@ func TestExecBuildX(t *testing.T) {
 	obj := tg.path("main")
 	tg.run("build", "-x", "-o", obj, src)
 	sh := tg.path("test.sh")
-	err := ioutil.WriteFile(sh, []byte("set -e\n"+tg.getStderr()), 0666)
+	cmds := tg.getStderr()
+	err := ioutil.WriteFile(sh, []byte("set -e\n"+cmds), 0666)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -5051,6 +5080,12 @@ func TestExecBuildX(t *testing.T) {
 	if string(out) != "hello" {
 		t.Fatalf("got %q; want %q", out, "hello")
 	}
+
+	matches := regexp.MustCompile(`^WORK=(.*)\n`).FindStringSubmatch(cmds)
+	if len(matches) == 0 {
+		t.Fatal("no WORK directory")
+	}
+	tg.must(os.RemoveAll(matches[1]))
 }
 
 func TestParallelNumber(t *testing.T) {

libgo/go/cmd/go/internal/base/base.go

@@ -82,7 +82,8 @@ func (c *Command) Name() string {
 func (c *Command) Usage() {
 	fmt.Fprintf(os.Stderr, "usage: %s\n", c.UsageLine)
 	fmt.Fprintf(os.Stderr, "Run 'go help %s' for details.\n", c.LongName())
-	os.Exit(2)
+	SetExitStatus(2)
+	Exit()
 }
 
 // Runnable reports whether the command can be run; otherwise

libgo/go/cmd/go/internal/cmdflag/flag.go

@@ -66,7 +66,8 @@ func SyntaxError(cmd, msg string) {
 	} else {
 		fmt.Fprintf(os.Stderr, `run "go help %s" for more information`+"\n", cmd)
 	}
-	os.Exit(2)
+	base.SetExitStatus(2)
+	base.Exit()
 }
 
 // AddKnownFlags registers the flags in defns with base.AddKnownFlag.

libgo/go/cmd/go/internal/help/help.go

@@ -63,7 +63,8 @@ Args:
 			helpSuccess = " " + strings.Join(args[:i], " ")
 		}
 		fmt.Fprintf(os.Stderr, "go help %s: unknown help topic. Run '%s'.\n", strings.Join(args, " "), helpSuccess)
-		os.Exit(2) // failed at 'go help cmd'
+		base.SetExitStatus(2) // failed at 'go help cmd'
+		base.Exit()
 	}
 
 	if len(cmd.Commands) > 0 {
@@ -167,7 +168,8 @@ func tmpl(w io.Writer, text string, data interface{}) {
 	if ew.err != nil {
 		// I/O error writing. Ignore write on closed pipe.
 		if strings.Contains(ew.err.Error(), "pipe") {
-			os.Exit(1)
+			base.SetExitStatus(1)
+			base.Exit()
 		}
 		base.Fatalf("writing output: %v", ew.err)
 	}

libgo/go/cmd/go/internal/vet/vetflag.go

@@ -76,7 +76,8 @@ func vetFlags(usage func(), args []string) (passToVet, packageNames []string) {
 	vetcmd.Stdout = out
 	if err := vetcmd.Run(); err != nil {
 		fmt.Fprintf(os.Stderr, "go vet: can't execute %s -flags: %v\n", tool, err)
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 	var analysisFlags []struct {
 		Name  string
@@ -85,7 +86,8 @@ func vetFlags(usage func(), args []string) (passToVet, packageNames []string) {
 	}
 	if err := json.Unmarshal(out.Bytes(), &analysisFlags); err != nil {
 		fmt.Fprintf(os.Stderr, "go vet: can't unmarshal JSON from %s -flags: %v", tool, err)
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 
 	// Add vet's flags to vetflagDefn.
@@ -134,7 +136,8 @@ func vetFlags(usage func(), args []string) (passToVet, packageNames []string) {
 		if f == nil {
 			fmt.Fprintf(os.Stderr, "vet: flag %q not defined\n", args[i])
 			fmt.Fprintf(os.Stderr, "Run \"go help vet\" for more information\n")
-			os.Exit(2)
+			base.SetExitStatus(2)
+			base.Exit()
 		}
 		if f.Value != nil {
 			if err := f.Value.Set(value); err != nil {
@@ -182,5 +185,6 @@ func usage() {
 	}
 	fmt.Fprintf(os.Stderr, "Run '%s -help' for the vet tool's flags.\n", cmd)
 
-	os.Exit(2)
+	base.SetExitStatus(2)
+	base.Exit()
 }

libgo/go/cmd/go/internal/work/action.go

@@ -249,12 +249,14 @@ func (b *Builder) Init() {
 
 	if _, ok := cfg.OSArchSupportsCgo[cfg.Goos+"/"+cfg.Goarch]; !ok && cfg.BuildContext.Compiler == "gc" {
 		fmt.Fprintf(os.Stderr, "cmd/go: unsupported GOOS/GOARCH pair %s/%s\n", cfg.Goos, cfg.Goarch)
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 	for _, tag := range cfg.BuildContext.BuildTags {
 		if strings.Contains(tag, ",") {
 			fmt.Fprintf(os.Stderr, "cmd/go: -tags space-separated list contains comma\n")
-			os.Exit(2)
+			base.SetExitStatus(2)
+			base.Exit()
 		}
 	}
 }

libgo/go/cmd/go/internal/work/exec.go

@@ -2334,7 +2334,7 @@ func (b *Builder) gccSupportsFlag(compiler []string, flag string) bool {
 	// version of GCC, so some systems have frozen on it.
 	// Now we pass an empty file on stdin, which should work at least for
 	// GCC and clang.
-	cmdArgs := str.StringList(compiler, flag, "-c", "-x", "c", "-")
+	cmdArgs := str.StringList(compiler, flag, "-c", "-x", "c", "-", "-o", os.DevNull)
 	if cfg.BuildN || cfg.BuildX {
 		b.Showcmd(b.WorkDir, "%s || true", joinUnambiguously(cmdArgs))
 		if cfg.BuildN {

libgo/go/cmd/go/internal/work/gccgo.go

@@ -56,7 +56,8 @@ func checkGccgoBin() {
 		return
 	}
 	fmt.Fprintf(os.Stderr, "cmd/go: gccgo: %s\n", gccgoErr)
-	os.Exit(2)
+	base.SetExitStatus(2)
+	base.Exit()
 }
 
 func (tools gccgoToolchain) gc(b *Builder, a *Action, archive string, importcfg []byte, symabis string, asmhdr bool, gofiles []string) (ofile string, output []byte, err error) {

libgo/go/cmd/go/internal/work/init.go

@@ -29,7 +29,8 @@ func BuildInit() {
 		p, err := filepath.Abs(cfg.BuildPkgdir)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "go %s: evaluating -pkgdir: %v\n", flag.Args()[0], err)
-			os.Exit(2)
+			base.SetExitStatus(2)
+			base.Exit()
 		}
 		cfg.BuildPkgdir = p
 	}
@@ -41,16 +42,19 @@ func instrumentInit() {
 	}
 	if cfg.BuildRace && cfg.BuildMSan {
 		fmt.Fprintf(os.Stderr, "go %s: may not use -race and -msan simultaneously\n", flag.Args()[0])
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 	if cfg.BuildMSan && !sys.MSanSupported(cfg.Goos, cfg.Goarch) {
 		fmt.Fprintf(os.Stderr, "-msan is not supported on %s/%s\n", cfg.Goos, cfg.Goarch)
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 	if cfg.BuildRace {
 		if !sys.RaceDetectorSupported(cfg.Goos, cfg.Goarch) {
 			fmt.Fprintf(os.Stderr, "go %s: -race is only supported on linux/amd64, linux/ppc64le, linux/arm64, freebsd/amd64, netbsd/amd64, darwin/amd64 and windows/amd64\n", flag.Args()[0])
-			os.Exit(2)
+			base.SetExitStatus(2)
+			base.Exit()
 		}
 	}
 	mode := "race"
@@ -61,7 +65,8 @@ func instrumentInit() {
 
 	if !cfg.BuildContext.CgoEnabled {
 		fmt.Fprintf(os.Stderr, "go %s: %s requires cgo; enable cgo by setting CGO_ENABLED=1\n", flag.Args()[0], modeFlag)
-		os.Exit(2)
+		base.SetExitStatus(2)
+		base.Exit()
 	}
 	forcedGcflags = append(forcedGcflags, modeFlag)
 	forcedLdflags = append(forcedLdflags, modeFlag)

libgo/go/cmd/go/script_test.go

@@ -400,6 +400,7 @@ func (ts *testScript) cmdCc(neg bool, args []string) {
 	var b work.Builder
 	b.Init()
 	ts.cmdExec(neg, append(b.GccCmd(".", ""), args...))
+	os.RemoveAll(b.WorkDir)
 }
 
 // cd changes to a different directory.