math,os,os/*: use testenv.Executable

As some callers don't have a testing context, modify testenv.Executable
to accept nil (similar to how testenv.GOROOT works).

Change-Id: I39112a7869933785a26b5cb6520055b3cc42b847
Reviewed-on: https://go-review.googlesource.com/c/go/+/609835
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

2 files changed, 7 insertions, 38 deletions

diff --git a/src/os/exec/exec_test.go b/src/os/exec/exec_test.go
index a0bb89e203..fd185cadcf 100644
--- a/src/os/exec/exec_test.go
+++ b/src/os/exec/exec_test.go
@@ -159,42 +159,16 @@ func helperCommandContext(t *testing.T, ctx context.Context, name string, args .
 	helperCommandUsed.LoadOrStore(name, true)
 
 	t.Helper()
-	testenv.MustHaveExec(t)
-
+	exe := testenv.Executable(t)
 	cs := append([]string{name}, args...)
 	if ctx != nil {
-		cmd = exec.CommandContext(ctx, exePath(t), cs...)
+		cmd = exec.CommandContext(ctx, exe, cs...)
 	} else {
-		cmd = exec.Command(exePath(t), cs...)
+		cmd = exec.Command(exe, cs...)
 	}
 	return cmd
 }
 
-// exePath returns the path to the running executable.
-func exePath(t testing.TB) string {
-	exeOnce.Do(func() {
-		// Use os.Executable instead of os.Args[0] in case the caller modifies
-		// cmd.Dir: if the test binary is invoked like "./exec.test", it should
-		// not fail spuriously.
-		exeOnce.path, exeOnce.err = os.Executable()
-	})
-
-	if exeOnce.err != nil {
-		if t == nil {
-			panic(exeOnce.err)
-		}
-		t.Fatal(exeOnce.err)
-	}
-
-	return exeOnce.path
-}
-
-var exeOnce struct {
-	path string
-	err  error
-	sync.Once
-}
-
 func chdir(t *testing.T, dir string) {
 	t.Helper()
 
@@ -1201,7 +1175,7 @@ func cmdHang(args ...string) {
 	pid := os.Getpid()
 
 	if *subsleep != 0 {
-		cmd := exec.Command(exePath(nil), "hang", subsleep.String(), "-read=true", "-probe="+probe.String())
+		cmd := exec.Command(testenv.Executable(nil), "hang", subsleep.String(), "-read=true", "-probe="+probe.String())
 		cmd.Stdin = os.Stdin
 		cmd.Stderr = os.Stderr
 		out, err := cmd.StdoutPipe()
diff --git a/src/os/exec/lp_windows_test.go b/src/os/exec/lp_windows_test.go
index a92a29799f..15b2a0032f 100644
--- a/src/os/exec/lp_windows_test.go
+++ b/src/os/exec/lp_windows_test.go
@@ -25,13 +25,8 @@ func init() {
 	registerHelperCommand("printpath", cmdPrintPath)
 }
 
-func cmdPrintPath(args ...string) {
-	exe, err := os.Executable()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "Executable: %v\n", err)
-		os.Exit(1)
-	}
-	fmt.Println(exe)
+func cmdPrintPath(_ ...string) {
+	fmt.Println(testenv.Executable(nil))
 }
 
 // makePATH returns a PATH variable referring to the
@@ -82,7 +77,7 @@ func installProgs(t *testing.T, root string, files []string) {
 // (We use a copy instead of just a symlink to ensure that os.Executable
 // always reports an unambiguous path, regardless of how it is implemented.)
 func installExe(t *testing.T, dstPath string) {
-	src, err := os.Open(exePath(t))
+	src, err := os.Open(testenv.Executable(t))
 	if err != nil {
 		t.Fatal(err)
 	}