debug/gosym: clean up and modernize pclntab_test

The self tests do not need to build the binary; they won't read it.  The
self tests should work on any ELF system.

Use t.Skip instead of panic.  Use internal/testenv.  Don't worry about a
space in the temporary directory name.

Change-Id: I66ef0af90520d330820afa7b6c6b3a132ab27454
Reviewed-on: https://go-review.googlesource.com/15495
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/debug/gosym/pclntab_test.go

@@ -6,6 +6,7 @@ package gosym
 
 import (
 	"debug/elf"
+	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -20,25 +21,16 @@ var (
 	pclinetestBinary string
 )
 
-func dotest(self bool) bool {
+func dotest(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
 	// For now, only works on amd64 platforms.
 	if runtime.GOARCH != "amd64" {
-		return false
-	}
-	// Self test reads test binary; only works on Linux.
-	if self && runtime.GOOS != "linux" {
-		return false
-	}
-	if pclinetestBinary != "" {
-		return true
+		t.Skipf("skipping on non-AMD64 system %s", runtime.GOARCH)
 	}
 	var err error
 	pclineTempDir, err = ioutil.TempDir("", "pclinetest")
 	if err != nil {
-		panic(err)
-	}
-	if strings.Contains(pclineTempDir, " ") {
-		panic("unexpected space in tempdir")
+		t.Fatal(err)
 	}
 	// This command builds pclinetest from pclinetest.asm;
 	// the resulting binary looks like it was built from pclinetest.s,
@@ -48,16 +40,15 @@ func dotest(self bool) bool {
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	if err := cmd.Run(); err != nil {
-		panic(err)
+		t.Fatal(err)
 	}
 	cmd = exec.Command("go", "tool", "link", "-H", "linux", "-E", "main",
 		"-o", pclinetestBinary, pclinetestBinary+".o")
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
 	if err := cmd.Run(); err != nil {
-		panic(err)
+		t.Fatal(err)
 	}
-	return true
 }
 
 func endtest() {
@@ -68,6 +59,17 @@ func endtest() {
 	}
 }
 
+// skipIfNotELF skips the test if we are not running on an ELF system.
+// These tests open and examine the test binary, and use elf.Open to do so.
+func skipIfNotELF(t *testing.T) {
+	switch runtime.GOOS {
+	case "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "solaris":
+		// OK.
+	default:
+		t.Skipf("skipping on non-ELF system %s", runtime.GOOS)
+	}
+}
+
 func getTable(t *testing.T) *Table {
 	f, tab := crack(os.Args[0], t)
 	f.Close()
@@ -112,10 +114,7 @@ func parse(file string, f *elf.File, t *testing.T) (*elf.File, *Table) {
 var goarch = os.Getenv("O")
 
 func TestLineFromAline(t *testing.T) {
-	if !dotest(true) {
-		return
-	}
-	defer endtest()
+	skipIfNotELF(t)
 
 	tab := getTable(t)
 	if tab.go12line != nil {
@@ -164,10 +163,7 @@ func TestLineFromAline(t *testing.T) {
 }
 
 func TestLineAline(t *testing.T) {
-	if !dotest(true) {
-		return
-	}
-	defer endtest()
+	skipIfNotELF(t)
 
 	tab := getTable(t)
 	if tab.go12line != nil {
@@ -210,9 +206,7 @@ func TestLineAline(t *testing.T) {
 }
 
 func TestPCLine(t *testing.T) {
-	if !dotest(false) {
-		return
-	}
+	dotest(t)
 	defer endtest()
 
 	f, tab := crack(pclinetestBinary, t)