misc/cgo/testsanitizers/cc_test.go - go - Git at Google

 // Copyright 2017 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.

 // sanitizers_test checks the use of Go with sanitizers like msan, asan, etc.
 // See https://github.com/google/sanitizers.
 package sanitizers_test

 import (
 	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"regexp"
 	"strconv"
 	"strings"
 	"sync"
 	"syscall"
 	"testing"
 	"unicode"
 )

 var overcommit struct {
 	sync.Once
 	value int
 	err   error
 }

 // requireOvercommit skips t if the kernel does not allow overcommit.
 func requireOvercommit(t *testing.T) {
 	t.Helper()

 	overcommit.Once.Do(func() {
 		var out []byte
 		out, overcommit.err = ioutil.ReadFile("/proc/sys/vm/overcommit_memory")
 		if overcommit.err != nil {
 			return
 		}
 		overcommit.value, overcommit.err = strconv.Atoi(string(bytes.TrimSpace(out)))
 	})

 	if overcommit.err != nil {
 		t.Skipf("couldn't determine vm.overcommit_memory (%v); assuming no overcommit", overcommit.err)
 	}
 	if overcommit.value == 2 {
 		t.Skip("vm.overcommit_memory=2")
 	}
 }

 var env struct {
 	sync.Once
 	m   map[string]string
 	err error
 }

 // goEnv returns the output of $(go env) as a map.
 func goEnv(key string) (string, error) {
 	env.Once.Do(func() {
 		var out []byte
 		out, env.err = exec.Command("go", "env", "-json").Output()
 		if env.err != nil {
 			return
 		}

 		env.m = make(map[string]string)
 		env.err = json.Unmarshal(out, &env.m)
 	})
 	if env.err != nil {
 		return "", env.err
 	}

 	v, ok := env.m[key]
 	if !ok {
 		return "", fmt.Errorf("`go env`: no entry for %v", key)
 	}
 	return v, nil
 }

 // replaceEnv sets the key environment variable to value in cmd.
 func replaceEnv(cmd *exec.Cmd, key, value string) {
 	if cmd.Env == nil {
 		cmd.Env = os.Environ()
 	}
 	cmd.Env = append(cmd.Env, key+"="+value)
 }

 // mustRun executes t and fails cmd with a well-formatted message if it fails.
 func mustRun(t *testing.T, cmd *exec.Cmd) {
 	t.Helper()
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		t.Fatalf("%#q exited with %v\n%s", strings.Join(cmd.Args, " "), err, out)
 	}
 }

 // cc returns a cmd that executes `$(go env CC) $(go env GOGCCFLAGS) $args`.
 func cc(args ...string) (*exec.Cmd, error) {
 	CC, err := goEnv("CC")
 	if err != nil {
 		return nil, err
 	}

 	GOGCCFLAGS, err := goEnv("GOGCCFLAGS")
 	if err != nil {
 		return nil, err
 	}

 	// Split GOGCCFLAGS, respecting quoting.
 	//
 	// TODO(bcmills): This code also appears in
 	// misc/cgo/testcarchive/carchive_test.go, and perhaps ought to go in
 	// src/cmd/dist/test.go as well. Figure out where to put it so that it can be
 	// shared.
 	var flags []string
 	quote := '\000'
 	start := 0
 	lastSpace := true
 	backslash := false
 	for i, c := range GOGCCFLAGS {
 		if quote == '\000' && unicode.IsSpace(c) {
 			if !lastSpace {
 				flags = append(flags, GOGCCFLAGS[start:i])
 				lastSpace = true
 			}
 		} else {
 			if lastSpace {
 				start = i
 				lastSpace = false
 			}
 			if quote == '\000' && !backslash && (c == '"' || c == '\'') {
 				quote = c
 				backslash = false
 			} else if !backslash && quote == c {
 				quote = '\000'
 			} else if (quote == '\000' || quote == '"') && !backslash && c == '\\' {
 				backslash = true
 			} else {
 				backslash = false
 			}
 		}
 	}
 	if !lastSpace {
 		flags = append(flags, GOGCCFLAGS[start:])
 	}

 	cmd := exec.Command(CC, flags...)
 	cmd.Args = append(cmd.Args, args...)
 	return cmd, nil
 }

 type version struct {
 	name         string
 	major, minor int
 }

 var compiler struct {
 	sync.Once
 	version
 	err error
 }

 // compilerVersion detects the version of $(go env CC).
 //
 // It returns a non-nil error if the compiler matches a known version schema but
 // the version could not be parsed, or if $(go env CC) could not be determined.
 func compilerVersion() (version, error) {
 	compiler.Once.Do(func() {
 		compiler.err = func() error {
 			compiler.name = "unknown"

 			cmd, err := cc("--version")
 			if err != nil {
 				return err
 			}
 			out, err := cmd.Output()
 			if err != nil {
 				// Compiler does not support "--version" flag: not Clang or GCC.
 				return nil
 			}

 			var match [][]byte
 			if bytes.HasPrefix(out, []byte("gcc")) {
 				compiler.name = "gcc"

 				cmd, err := cc("-dumpversion")
 				if err != nil {
 					return err
 				}
 				out, err := cmd.Output()
 				if err != nil {
 					// gcc, but does not support gcc's "-dumpversion" flag?!
 					return err
 				}
 				gccRE := regexp.MustCompile(`(\d+)\.(\d+)`)
 				match = gccRE.FindSubmatch(out)
 			} else {
 				clangRE := regexp.MustCompile(`clang version (\d+)\.(\d+)`)
 				if match = clangRE.FindSubmatch(out); len(match) > 0 {
 					compiler.name = "clang"
 				}
 			}

 			if len(match) < 3 {
 				return nil // "unknown"
 			}
 			if compiler.major, err = strconv.Atoi(string(match[1])); err != nil {
 				return err
 			}
 			if compiler.minor, err = strconv.Atoi(string(match[2])); err != nil {
 				return err
 			}
 			return nil
 		}()
 	})
 	return compiler.version, compiler.err
 }

 type compilerCheck struct {
 	once sync.Once
 	err  error
 	skip bool // If true, skip with err instead of failing with it.
 }

 type config struct {
 	sanitizer string

 	cFlags, ldFlags, goFlags []string

 	sanitizerCheck, runtimeCheck compilerCheck
 }

 var configs struct {
 	sync.Mutex
 	m map[string]*config
 }

 // configure returns the configuration for the given sanitizer.
 func configure(sanitizer string) *config {
 	configs.Lock()
 	defer configs.Unlock()
 	if c, ok := configs.m[sanitizer]; ok {
 		return c
 	}

 	c := &config{
 		sanitizer: sanitizer,
 		cFlags:    []string{"-fsanitize=" + sanitizer},
 		ldFlags:   []string{"-fsanitize=" + sanitizer},
 	}

 	if testing.Verbose() {
 		c.goFlags = append(c.goFlags, "-x")
 	}

 	switch sanitizer {
 	case "memory":
 		c.goFlags = append(c.goFlags, "-msan")

 	case "thread":
 		c.goFlags = append(c.goFlags, "--installsuffix=tsan")
 		compiler, _ := compilerVersion()
 		if compiler.name == "gcc" {
 			c.cFlags = append(c.cFlags, "-fPIC")
 			c.ldFlags = append(c.ldFlags, "-fPIC", "-static-libtsan")
 		}

 	default:
 		panic(fmt.Sprintf("unrecognized sanitizer: %q", sanitizer))
 	}

 	if configs.m == nil {
 		configs.m = make(map[string]*config)
 	}
 	configs.m[sanitizer] = c
 	return c
 }

 // goCmd returns a Cmd that executes "go $subcommand $args" with appropriate
 // additional flags and environment.
 func (c *config) goCmd(subcommand string, args ...string) *exec.Cmd {
 	cmd := exec.Command("go", subcommand)
 	cmd.Args = append(cmd.Args, c.goFlags...)
 	cmd.Args = append(cmd.Args, args...)
 	replaceEnv(cmd, "CGO_CFLAGS", strings.Join(c.cFlags, " "))
 	replaceEnv(cmd, "CGO_LDFLAGS", strings.Join(c.ldFlags, " "))
 	return cmd
 }

 // skipIfCSanitizerBroken skips t if the C compiler does not produce working
 // binaries as configured.
 func (c *config) skipIfCSanitizerBroken(t *testing.T) {
 	check := &c.sanitizerCheck
 	check.once.Do(func() {
 		check.skip, check.err = c.checkCSanitizer()
 	})
 	if check.err != nil {
 		t.Helper()
 		if check.skip {
 			t.Skip(check.err)
 		}
 		t.Fatal(check.err)
 	}
 }

 var cMain = []byte(`
 int main() {
 	return 0;
 }
 `)

 func (c *config) checkCSanitizer() (skip bool, err error) {
 	dir, err := ioutil.TempDir("", c.sanitizer)
 	if err != nil {
 		return false, fmt.Errorf("failed to create temp directory: %v", err)
 	}
 	defer os.RemoveAll(dir)

 	src := filepath.Join(dir, "return0.c")
 	if err := ioutil.WriteFile(src, cMain, 0600); err != nil {
 		return false, fmt.Errorf("failed to write C source file: %v", err)
 	}

 	dst := filepath.Join(dir, "return0")
 	cmd, err := cc(c.cFlags...)
 	if err != nil {
 		return false, err
 	}
 	cmd.Args = append(cmd.Args, c.ldFlags...)
 	cmd.Args = append(cmd.Args, "-o", dst, src)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		if bytes.Contains(out, []byte("-fsanitize")) &&
 			(bytes.Contains(out, []byte("unrecognized")) ||
 				bytes.Contains(out, []byte("unsupported"))) {
 			return true, errors.New(string(out))
 		}
 		return true, fmt.Errorf("%#q failed: %v\n%s", strings.Join(cmd.Args, " "), err, out)
 	}

 	if out, err := exec.Command(dst).CombinedOutput(); err != nil {
 		if os.IsNotExist(err) {
 			return true, fmt.Errorf("%#q failed to produce executable: %v", strings.Join(cmd.Args, " "), err)
 		}
 		snippet := bytes.SplitN(out, []byte{'\n'}, 2)[0]
 		return true, fmt.Errorf("%#q generated broken executable: %v\n%s", strings.Join(cmd.Args, " "), err, snippet)
 	}

 	return false, nil
 }

 // skipIfRuntimeIncompatible skips t if the Go runtime is suspected not to work
 // with cgo as configured.
 func (c *config) skipIfRuntimeIncompatible(t *testing.T) {
 	check := &c.runtimeCheck
 	check.once.Do(func() {
 		check.skip, check.err = c.checkRuntime()
 	})
 	if check.err != nil {
 		t.Helper()
 		if check.skip {
 			t.Skip(check.err)
 		}
 		t.Fatal(check.err)
 	}
 }

 func (c *config) checkRuntime() (skip bool, err error) {
 	if c.sanitizer != "thread" {
 		return false, nil
 	}

 	// libcgo.h sets CGO_TSAN if it detects TSAN support in the C compiler.
 	// Dump the preprocessor defines to check that that works.
 	// (Sometimes it doesn't: see https://golang.org/issue/15983.)
 	cmd, err := cc(c.cFlags...)
 	if err != nil {
 		return false, err
 	}
 	cmd.Args = append(cmd.Args, "-dM", "-E", "../../../src/runtime/cgo/libcgo.h")
 	cmdStr := strings.Join(cmd.Args, " ")
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		return false, fmt.Errorf("%#q exited with %v\n%s", cmdStr, err, out)
 	}
 	if !bytes.Contains(out, []byte("#define CGO_TSAN")) {
 		return true, fmt.Errorf("%#q did not define CGO_TSAN", cmdStr)
 	}
 	return false, nil
 }

 // srcPath returns the path to the given file relative to this test's source tree.
 func srcPath(path string) string {
 	return filepath.Join("src", path)
 }

 // A tempDir manages a temporary directory within a test.
 type tempDir struct {
 	base string
 }

 func (d *tempDir) RemoveAll(t *testing.T) {
 	t.Helper()
 	if d.base == "" {
 		return
 	}
 	if err := os.RemoveAll(d.base); err != nil {
 		t.Fatalf("Failed to remove temp dir: %v", err)
 	}
 }

 func (d *tempDir) Join(name string) string {
 	return filepath.Join(d.base, name)
 }

 func newTempDir(t *testing.T) *tempDir {
 	t.Helper()
 	dir, err := ioutil.TempDir("", filepath.Dir(t.Name()))
 	if err != nil {
 		t.Fatalf("Failed to create temp dir: %v", err)
 	}
 	return &tempDir{base: dir}
 }

 // hangProneCmd returns an exec.Cmd for a command that is likely to hang.
 //
 // If one of these tests hangs, the caller is likely to kill the test process
 // using SIGINT, which will be sent to all of the processes in the test's group.
 // Unfortunately, TSAN in particular is prone to dropping signals, so the SIGINT
 // may terminate the test binary but leave the subprocess running. hangProneCmd
 // configures subprocess to receive SIGKILL instead to ensure that it won't
 // leak.
 func hangProneCmd(name string, arg ...string) *exec.Cmd {
 	cmd := exec.Command(name, arg...)
 	cmd.SysProcAttr = &syscall.SysProcAttr{
 		Pdeathsig: syscall.SIGKILL,
 	}
 	return cmd
 }
	// Copyright 2017 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.

	// sanitizers_test checks the use of Go with sanitizers like msan, asan, etc.
	// See https://github.com/google/sanitizers.
	package sanitizers_test

	import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"testing"
	"unicode"
	)

	var overcommit struct {
	sync.Once
	value int
	err error
	}

	// requireOvercommit skips t if the kernel does not allow overcommit.
	func requireOvercommit(t *testing.T) {
	t.Helper()

	overcommit.Once.Do(func() {
	var out []byte
	out, overcommit.err = ioutil.ReadFile("/proc/sys/vm/overcommit_memory")
	if overcommit.err != nil {
	return
	}
	overcommit.value, overcommit.err = strconv.Atoi(string(bytes.TrimSpace(out)))
	})

	if overcommit.err != nil {
	t.Skipf("couldn't determine vm.overcommit_memory (%v); assuming no overcommit", overcommit.err)
	}
	if overcommit.value == 2 {
	t.Skip("vm.overcommit_memory=2")
	}
	}

	var env struct {
	sync.Once
	m map[string]string
	err error
	}

	// goEnv returns the output of $(go env) as a map.
	func goEnv(key string) (string, error) {
	env.Once.Do(func() {
	var out []byte
	out, env.err = exec.Command("go", "env", "-json").Output()
	if env.err != nil {
	return
	}

	env.m = make(map[string]string)
	env.err = json.Unmarshal(out, &env.m)
	})
	if env.err != nil {
	return "", env.err
	}

	v, ok := env.m[key]
	if !ok {
	return "", fmt.Errorf("`go env`: no entry for %v", key)
	}
	return v, nil
	}

	// replaceEnv sets the key environment variable to value in cmd.
	func replaceEnv(cmd *exec.Cmd, key, value string) {
	if cmd.Env == nil {
	cmd.Env = os.Environ()
	}
	cmd.Env = append(cmd.Env, key+"="+value)
	}

	// mustRun executes t and fails cmd with a well-formatted message if it fails.
	func mustRun(t testing.T, cmd exec.Cmd) {
	t.Helper()
	out, err := cmd.CombinedOutput()
	if err != nil {
	t.Fatalf("%#q exited with %v\n%s", strings.Join(cmd.Args, " "), err, out)
	}
	}

	// cc returns a cmd that executes `$(go env CC) $(go env GOGCCFLAGS) $args`.
	func cc(args ...string) (*exec.Cmd, error) {
	CC, err := goEnv("CC")
	if err != nil {
	return nil, err
	}

	GOGCCFLAGS, err := goEnv("GOGCCFLAGS")
	if err != nil {
	return nil, err
	}

	// Split GOGCCFLAGS, respecting quoting.
	//
	// TODO(bcmills): This code also appears in
	// misc/cgo/testcarchive/carchive_test.go, and perhaps ought to go in
	// src/cmd/dist/test.go as well. Figure out where to put it so that it can be
	// shared.
	var flags []string
	quote := '\000'
	start := 0
	lastSpace := true
	backslash := false
	for i, c := range GOGCCFLAGS {
	if quote == '\000' && unicode.IsSpace(c) {
	if !lastSpace {
	flags = append(flags, GOGCCFLAGS[start:i])
	lastSpace = true
	}
	} else {
	if lastSpace {
	start = i
	lastSpace = false
	}
	if quote == '\000' && !backslash && (c == '"' \|\| c == '\'') {
	quote = c
	backslash = false
	} else if !backslash && quote == c {
	quote = '\000'
	} else if (quote == '\000' \|\| quote == '"') && !backslash && c == '\\' {
	backslash = true
	} else {
	backslash = false
	}
	}
	}
	if !lastSpace {
	flags = append(flags, GOGCCFLAGS[start:])
	}

	cmd := exec.Command(CC, flags...)
	cmd.Args = append(cmd.Args, args...)
	return cmd, nil
	}

	type version struct {
	name string
	major, minor int
	}

	var compiler struct {
	sync.Once
	version
	err error
	}

	// compilerVersion detects the version of $(go env CC).
	//
	// It returns a non-nil error if the compiler matches a known version schema but
	// the version could not be parsed, or if $(go env CC) could not be determined.
	func compilerVersion() (version, error) {
	compiler.Once.Do(func() {
	compiler.err = func() error {
	compiler.name = "unknown"

	cmd, err := cc("--version")
	if err != nil {
	return err
	}
	out, err := cmd.Output()
	if err != nil {
	// Compiler does not support "--version" flag: not Clang or GCC.
	return nil
	}

	var match [][]byte
	if bytes.HasPrefix(out, []byte("gcc")) {
	compiler.name = "gcc"

	cmd, err := cc("-dumpversion")
	if err != nil {
	return err
	}
	out, err := cmd.Output()
	if err != nil {
	// gcc, but does not support gcc's "-dumpversion" flag?!
	return err
	}
	gccRE := regexp.MustCompile(`(\d+)\.(\d+)`)
	match = gccRE.FindSubmatch(out)
	} else {
	clangRE := regexp.MustCompile(`clang version (\d+)\.(\d+)`)
	if match = clangRE.FindSubmatch(out); len(match) > 0 {
	compiler.name = "clang"
	}
	}

	if len(match) < 3 {
	return nil // "unknown"
	}
	if compiler.major, err = strconv.Atoi(string(match[1])); err != nil {
	return err
	}
	if compiler.minor, err = strconv.Atoi(string(match[2])); err != nil {
	return err
	}
	return nil
	}()
	})
	return compiler.version, compiler.err
	}

	type compilerCheck struct {
	once sync.Once
	err error
	skip bool // If true, skip with err instead of failing with it.
	}

	type config struct {
	sanitizer string

	cFlags, ldFlags, goFlags []string

	sanitizerCheck, runtimeCheck compilerCheck
	}

	var configs struct {
	sync.Mutex
	m map[string]*config
	}

	// configure returns the configuration for the given sanitizer.
	func configure(sanitizer string) *config {
	configs.Lock()
	defer configs.Unlock()
	if c, ok := configs.m[sanitizer]; ok {
	return c
	}

	c := &config{
	sanitizer: sanitizer,
	cFlags: []string{"-fsanitize=" + sanitizer},
	ldFlags: []string{"-fsanitize=" + sanitizer},
	}

	if testing.Verbose() {
	c.goFlags = append(c.goFlags, "-x")
	}

	switch sanitizer {
	case "memory":
	c.goFlags = append(c.goFlags, "-msan")

	case "thread":
	c.goFlags = append(c.goFlags, "--installsuffix=tsan")
	compiler, _ := compilerVersion()
	if compiler.name == "gcc" {
	c.cFlags = append(c.cFlags, "-fPIC")
	c.ldFlags = append(c.ldFlags, "-fPIC", "-static-libtsan")
	}

	default:
	panic(fmt.Sprintf("unrecognized sanitizer: %q", sanitizer))
	}

	if configs.m == nil {
	configs.m = make(map[string]*config)
	}
	configs.m[sanitizer] = c
	return c
	}

	// goCmd returns a Cmd that executes "go $subcommand $args" with appropriate
	// additional flags and environment.
	func (c config) goCmd(subcommand string, args ...string) exec.Cmd {
	cmd := exec.Command("go", subcommand)
	cmd.Args = append(cmd.Args, c.goFlags...)
	cmd.Args = append(cmd.Args, args...)
	replaceEnv(cmd, "CGO_CFLAGS", strings.Join(c.cFlags, " "))
	replaceEnv(cmd, "CGO_LDFLAGS", strings.Join(c.ldFlags, " "))
	return cmd
	}

	// skipIfCSanitizerBroken skips t if the C compiler does not produce working
	// binaries as configured.
	func (c config) skipIfCSanitizerBroken(t testing.T) {
	check := &c.sanitizerCheck
	check.once.Do(func() {
	check.skip, check.err = c.checkCSanitizer()
	})
	if check.err != nil {
	t.Helper()
	if check.skip {
	t.Skip(check.err)
	}
	t.Fatal(check.err)
	}
	}

	var cMain = []byte(`
	int main() {
	return 0;
	}
	`)

	func (c *config) checkCSanitizer() (skip bool, err error) {
	dir, err := ioutil.TempDir("", c.sanitizer)
	if err != nil {
	return false, fmt.Errorf("failed to create temp directory: %v", err)
	}
	defer os.RemoveAll(dir)

	src := filepath.Join(dir, "return0.c")
	if err := ioutil.WriteFile(src, cMain, 0600); err != nil {
	return false, fmt.Errorf("failed to write C source file: %v", err)
	}

	dst := filepath.Join(dir, "return0")
	cmd, err := cc(c.cFlags...)
	if err != nil {
	return false, err
	}
	cmd.Args = append(cmd.Args, c.ldFlags...)
	cmd.Args = append(cmd.Args, "-o", dst, src)
	out, err := cmd.CombinedOutput()
	if err != nil {
	if bytes.Contains(out, []byte("-fsanitize")) &&
	(bytes.Contains(out, []byte("unrecognized")) \|\|
	bytes.Contains(out, []byte("unsupported"))) {
	return true, errors.New(string(out))
	}
	return true, fmt.Errorf("%#q failed: %v\n%s", strings.Join(cmd.Args, " "), err, out)
	}

	if out, err := exec.Command(dst).CombinedOutput(); err != nil {
	if os.IsNotExist(err) {
	return true, fmt.Errorf("%#q failed to produce executable: %v", strings.Join(cmd.Args, " "), err)
	}
	snippet := bytes.SplitN(out, []byte{'\n'}, 2)[0]
	return true, fmt.Errorf("%#q generated broken executable: %v\n%s", strings.Join(cmd.Args, " "), err, snippet)
	}

	return false, nil
	}

	// skipIfRuntimeIncompatible skips t if the Go runtime is suspected not to work
	// with cgo as configured.
	func (c config) skipIfRuntimeIncompatible(t testing.T) {
	check := &c.runtimeCheck
	check.once.Do(func() {
	check.skip, check.err = c.checkRuntime()
	})
	if check.err != nil {
	t.Helper()
	if check.skip {
	t.Skip(check.err)
	}
	t.Fatal(check.err)
	}
	}

	func (c *config) checkRuntime() (skip bool, err error) {
	if c.sanitizer != "thread" {
	return false, nil
	}

	// libcgo.h sets CGO_TSAN if it detects TSAN support in the C compiler.
	// Dump the preprocessor defines to check that that works.
	// (Sometimes it doesn't: see https://golang.org/issue/15983.)
	cmd, err := cc(c.cFlags...)
	if err != nil {
	return false, err
	}
	cmd.Args = append(cmd.Args, "-dM", "-E", "../../../src/runtime/cgo/libcgo.h")
	cmdStr := strings.Join(cmd.Args, " ")
	out, err := cmd.CombinedOutput()
	if err != nil {
	return false, fmt.Errorf("%#q exited with %v\n%s", cmdStr, err, out)
	}
	if !bytes.Contains(out, []byte("#define CGO_TSAN")) {
	return true, fmt.Errorf("%#q did not define CGO_TSAN", cmdStr)
	}
	return false, nil
	}

	// srcPath returns the path to the given file relative to this test's source tree.
	func srcPath(path string) string {
	return filepath.Join("src", path)
	}

	// A tempDir manages a temporary directory within a test.
	type tempDir struct {
	base string
	}

	func (d tempDir) RemoveAll(t testing.T) {
	t.Helper()
	if d.base == "" {
	return
	}
	if err := os.RemoveAll(d.base); err != nil {
	t.Fatalf("Failed to remove temp dir: %v", err)
	}
	}

	func (d *tempDir) Join(name string) string {
	return filepath.Join(d.base, name)
	}

	func newTempDir(t testing.T) tempDir {
	t.Helper()
	dir, err := ioutil.TempDir("", filepath.Dir(t.Name()))
	if err != nil {
	t.Fatalf("Failed to create temp dir: %v", err)
	}
	return &tempDir{base: dir}
	}

	// hangProneCmd returns an exec.Cmd for a command that is likely to hang.
	//
	// If one of these tests hangs, the caller is likely to kill the test process
	// using SIGINT, which will be sent to all of the processes in the test's group.
	// Unfortunately, TSAN in particular is prone to dropping signals, so the SIGINT
	// may terminate the test binary but leave the subprocess running. hangProneCmd
	// configures subprocess to receive SIGKILL instead to ensure that it won't
	// leak.
	func hangProneCmd(name string, arg ...string) *exec.Cmd {
	cmd := exec.Command(name, arg...)
	cmd.SysProcAttr = &syscall.SysProcAttr{
	Pdeathsig: syscall.SIGKILL,
	}
	return cmd
	}