cmd/pprof: don't use offset if we don't have a start address

The test is in the runtime package because there are other tests of
pprof there. At some point we should probably move them all into a pprof
testsuite.

Fixes #16128.

Change-Id: Ieefa40c61cf3edde11fe0cf04da1debfd8b3d7c0
Reviewed-on: https://go-review.googlesource.com/24274
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

src/cmd/pprof/pprof.go

@@ -117,8 +117,10 @@ func (*objTool) Open(name string, start uint64) (plugin.ObjFile, error) {
 		name: name,
 		file: of,
 	}
-	if load, err := of.LoadAddress(); err == nil {
-		f.offset = start - load
+	if start != 0 {
+		if load, err := of.LoadAddress(); err == nil {
+			f.offset = start - load
+		}
 	}
 	return f, nil
 }

src/runtime/crash_test.go

@@ -442,3 +442,43 @@ func TestPanicDeadlockGosched(t *testing.T) {
 func TestPanicDeadlockSyscall(t *testing.T) {
 	testPanicDeadlock(t, "SyscallInPanic", "1\n2\npanic: 3\n\n")
 }
+
+func TestMemPprof(t *testing.T) {
+	testenv.MustHaveGoRun(t)
+
+	exe, err := buildTestProg(t, "testprog")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := testEnv(exec.Command(exe, "MemProf")).CombinedOutput()
+	if err != nil {
+		t.Fatal(err)
+	}
+	fn := strings.TrimSpace(string(got))
+	defer os.Remove(fn)
+
+	cmd := testEnv(exec.Command("go", "tool", "pprof", "-alloc_space", "-top", exe, fn))
+
+	found := false
+	for i, e := range cmd.Env {
+		if strings.HasPrefix(e, "PPROF_TMPDIR=") {
+			cmd.Env[i] = "PPROF_TMPDIR=" + os.TempDir()
+			found = true
+			break
+		}
+	}
+	if !found {
+		cmd.Env = append(cmd.Env, "PPROF_TMPDIR="+os.TempDir())
+	}
+
+	top, err := cmd.CombinedOutput()
+	t.Logf("%s", top)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !bytes.Contains(top, []byte("MemProf")) {
+		t.Error("missing MemProf in pprof output")
+	}
+}

src/runtime/testdata/testprog/memprof.go

+// Copyright 2016 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.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"runtime/pprof"
+)
+
+func init() {
+	register("MemProf", MemProf)
+}
+
+var memProfBuf bytes.Buffer
+var memProfStr string
+
+func MemProf() {
+	for i := 0; i < 1000; i++ {
+		fmt.Fprintf(&memProfBuf, "%*d\n", i, i)
+	}
+	memProfStr = memProfBuf.String()
+
+	runtime.GC()
+
+	f, err := ioutil.TempFile("", "memprof")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	if err := pprof.WriteHeapProfile(f); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	name := f.Name()
+	if err := f.Close(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	fmt.Println(name)
+}