cmd/objdump: speed up tests

Rebuild cmd/objdump once instead of twice.
Speeds up standalone 'go test cmd/objdump' on my
machine from ~1.4s to ~1s.

Updates #17751

Change-Id: I15fd79cf18c310f892bc28a9e9ca47ee010c989a
Reviewed-on: https://go-review.googlesource.com/32673
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/cmd/objdump/objdump_test.go b/src/cmd/objdump/objdump_test.go
index a41af9a5c6b43db16b430b8ed1c445c1dffd3312..4b70862d09d50a81f808ebb91e38916387931bde 100644 (file)
--- a/src/cmd/objdump/objdump_test.go
+++ b/src/cmd/objdump/objdump_test.go
@@ -6,6 +6,7 @@ package main
 
 import (
        "flag"
+       "fmt"
        "go/build"
        "internal/testenv"
        "io/ioutil"
@@ -17,21 +18,43 @@ import (
        "testing"
 )
 
-func buildObjdump(t *testing.T) (tmp, exe string) {
-       testenv.MustHaveGoBuild(t)
+var tmp, exe string // populated by buildObjdump
 
-       tmp, err := ioutil.TempDir("", "TestObjDump")
+func TestMain(m *testing.M) {
+       flag.Parse()
+       if !testenv.HasGoBuild() {
+               return
+       }
+       var exitcode int
+       if err := buildObjdump(); err == nil {
+               exitcode = m.Run()
+       } else {
+               fmt.Println(err)
+               exitcode = 1
+       }
+       os.RemoveAll(tmp)
+       os.Exit(exitcode)
+}
+
+func buildObjdump() error {
+       var err error
+       tmp, err = ioutil.TempDir("", "TestObjDump")
        if err != nil {
-               t.Fatal("TempDir failed: ", err)
+               return fmt.Errorf("TempDir failed: %v", err)
        }
 
        exe = filepath.Join(tmp, "testobjdump.exe")
-       out, err := exec.Command(testenv.GoToolPath(t), "build", "-o", exe, "cmd/objdump").CombinedOutput()
+       gotool, err := testenv.GoTool()
+       if err != nil {
+               return err
+       }
+       out, err := exec.Command(gotool, "build", "-o", exe, "cmd/objdump").CombinedOutput()
        if err != nil {
                os.RemoveAll(tmp)
-               t.Fatalf("go build -o %v cmd/objdump: %v\n%s", exe, err, string(out))
+               return fmt.Errorf("go build -o %v cmd/objdump: %v\n%s", exe, err, string(out))
        }
-       return
+
+       return nil
 }
 
 var x86Need = []string{
@@ -70,9 +93,6 @@ var target = flag.String("target", "", "test disassembly of `goos/goarch` binary
 // can handle that one.
 
 func testDisasm(t *testing.T, flags ...string) {
-       tmp, exe := buildObjdump(t)
-       defer os.RemoveAll(tmp)
-
        goarch := runtime.GOARCH
        if *target != "" {
                f := strings.Split(*target, "/")