misc/cgo/testshared: rewrite in Go

And fix to work on filesystems with only 1s resolution.

Fixes golang#10724

Change-Id: Ia07463f090b4290fc27f5953fa94186463d7afc7

Author: mwhudson

misc/cgo/testshared/shared_test.go

@@ -0,0 +1,362 @@
+// Copyright 2015 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 shared_test
+
+import (
+	"bufio"
+	"bytes"
+	"debug/elf"
+	"errors"
+	"flag"
+	"fmt"
+	"go/build"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+)
+
+var gopathInstallDir, gorootInstallDir, suffix string
+
+// This is the smallest set of packages we can link into a shared
+// library (runtime/cgo is built implicitly).
+var minpkgs = []string{"runtime", "sync/atomic"}
+var soname = "libruntime,sync-atomic.so"
+
+// run runs a command and calls t.Errorf if it fails.
+func run(t *testing.T, msg string, args ...string) {
+	c := exec.Command(args[0], args[1:]...)
+	if output, err := c.CombinedOutput(); err != nil {
+		t.Errorf("executing %s (%s) failed %s:\n%s", strings.Join(args, " "), msg, err, output)
+	}
+}
+
+// goCmd invokes the go tool with the installsuffix set up by TestMain. It calls
+// t.Errorf if the command fails.
+func goCmd(t *testing.T, args ...string) {
+	newargs := []string{args[0], "-installsuffix=" + suffix}
+	if testing.Verbose() {
+		newargs = append(newargs, "-v")
+	}
+	newargs = append(newargs, args[1:]...)
+	c := exec.Command("go", newargs...)
+	if testing.Verbose() {
+		fmt.Printf("+ go %s\n", strings.Join(newargs, " "))
+		c.Stdout = os.Stdout
+		c.Stderr = os.Stderr
+	}
+	if output, err := c.CombinedOutput(); err != nil {
+		t.Errorf("executing %s failed %v:\n%s", strings.Join(c.Args, " "), err, output)
+	}
+}
+
+// TestMain calls testMain so that the latter can use defer (TestMain exits with os.Exit).
+func testMain(m *testing.M) (int, error) {
+	// Because go install -buildmode=shared $standard_library_package always
+	// installs into $GOROOT, here are some gymnastics to come up with a unique
+	// installsuffix to use in this test that we can clean up afterwards.
+	myContext := build.Default
+	runtimeP, err := myContext.Import("runtime", ".", build.ImportComment)
+	if err != nil {
+		return 0, fmt.Errorf("import failed: %v", err)
+	}
+	for i := 0; i < 10000; i++ {
+		try := fmt.Sprintf("%s_%d_dynlink", runtimeP.PkgTargetRoot, rand.Int63())
+		err = os.Mkdir(try, 0700)
+		if os.IsExist(err) {
+			continue
+		}
+		if err == nil {
+			gorootInstallDir = try
+		}
+		break
+	}
+	if err != nil {
+		return 0, fmt.Errorf("can't create temporary directory: %v", err)
+	}
+	if gorootInstallDir == "" {
+		return 0, errors.New("could not create temporary directory after 10000 tries")
+	}
+	defer os.RemoveAll(gorootInstallDir)
+
+	// Some tests need to edit the source in GOPATH, so copy this directory to a
+	// temporary directory and chdir to that.
+	scratchDir, err := ioutil.TempDir("", "testshared")
+	if err != nil {
+		return 0, fmt.Errorf("TempDir failed: %v", err)
+	}
+	defer os.RemoveAll(scratchDir)
+	err = filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
+		scratchPath := filepath.Join(scratchDir, path)
+		if info.IsDir() {
+			if path == "." {
+				return nil
+			}
+			return os.Mkdir(scratchPath, info.Mode())
+		} else {
+			fromBytes, err := ioutil.ReadFile(path)
+			if err != nil {
+				return err
+			}
+			return ioutil.WriteFile(scratchPath, fromBytes, info.Mode())
+		}
+	})
+	if err != nil {
+		return 0, fmt.Errorf("walk failed: %v", err)
+	}
+	os.Setenv("GOPATH", scratchDir)
+	myContext.GOPATH = scratchDir
+	os.Chdir(scratchDir)
+
+	// All tests depend on runtime being built into a shared library. Because
+	// that takes a few seconds, do it here and have all tests use the version
+	// built here.
+	suffix = strings.Split(filepath.Base(gorootInstallDir), "_")[2]
+	goCmd(nil, append([]string{"install", "-buildmode=shared"}, minpkgs...)...)
+
+	myContext.InstallSuffix = suffix + "_dynlink"
+	depP, err := myContext.Import("dep", ".", build.ImportComment)
+	if err != nil {
+		return 0, fmt.Errorf("import failed: %v", err)
+	}
+	gopathInstallDir = depP.PkgTargetRoot
+	return m.Run(), nil
+}
+
+func TestMain(m *testing.M) {
+	flag.Parse()
+	exitCode, err := testMain(m)
+	if err != nil {
+		log.Fatal(err)
+	}
+	os.Exit(exitCode)
+}
+
+// The shared library was built at the expected location.
+func TestSOBuilt(t *testing.T) {
+	_, err := os.Stat(filepath.Join(gorootInstallDir, soname))
+	if err != nil {
+		t.Error(err)
+	}
+}
+
+// The install command should have created a "shlibname" file for the
+// listed packages (and runtime/cgo) indicating the name of the shared
+// library containing it.
+func TestShlibnameFiles(t *testing.T) {
+	pkgs := append([]string{}, minpkgs...)
+	pkgs = append(pkgs, "runtime/cgo")
+	for _, pkg := range pkgs {
+		shlibnamefile := filepath.Join(gorootInstallDir, pkg+".shlibname")
+		contentsb, err := ioutil.ReadFile(shlibnamefile)
+		if err != nil {
+			t.Errorf("error reading shlibnamefile for %s: %v", pkg, err)
+			continue
+		}
+		contents := strings.TrimSpace(string(contentsb))
+		if contents != soname {
+			t.Errorf("shlibnamefile for %s has wrong contents: %q", pkg, contents)
+		}
+	}
+}
+
+func dynStrings(path string, flag elf.DynTag) []string {
+	f, err := elf.Open(path)
+	defer f.Close()
+	if err != nil {
+		log.Fatal("elf.Open failed: ", err)
+	}
+	dynstrings, err := f.DynString(flag)
+	if err != nil {
+		log.Fatal("dynstring failed: ", err)
+	}
+	return dynstrings
+}
+
+func AssertIsLinkedTo(t *testing.T, path, lib string) {
+	for _, dynstring := range dynStrings(path, elf.DT_NEEDED) {
+		if dynstring == lib {
+			return
+		}
+	}
+	t.Errorf("%s is not linked to %s", path, lib)
+}
+
+func AssertHasRPath(t *testing.T, path, dir string) {
+	for _, dynstring := range dynStrings(path, elf.DT_RPATH) {
+		for _, rpath := range strings.Split(dynstring, ":") {
+			if filepath.Clean(rpath) == filepath.Clean(dir) {
+				return
+			}
+		}
+	}
+	t.Errorf("%s does not have rpath %s", path, dir)
+}
+
+// Build a trivial program that links against the shared runtime and check it runs.
+func TestTrivialExecutable(t *testing.T) {
+	goCmd(t, "install", "-linkshared", "trivial")
+	run(t, "trivial executable", "./bin/trivial")
+	AssertIsLinkedTo(t, "./bin/trivial", soname)
+	AssertHasRPath(t, "./bin/trivial", gorootInstallDir)
+}
+
+// Build a GOPATH package into a shared library that links against the goroot runtime
+// and an executable that links against both.
+func TestGOPathShlib(t *testing.T) {
+	goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+	AssertIsLinkedTo(t, filepath.Join(gopathInstallDir, "libdep.so"), soname)
+	goCmd(t, "install", "-linkshared", "exe")
+	AssertIsLinkedTo(t, "./bin/exe", soname)
+	AssertIsLinkedTo(t, "./bin/exe", "libdep.so")
+	AssertHasRPath(t, "./bin/exe", gorootInstallDir)
+	AssertHasRPath(t, "./bin/exe", gopathInstallDir)
+	// And check it runs.
+	run(t, "executable linked to GOPATH library", "./bin/exe")
+}
+
+// Testing rebuilding of shared libraries when they are stale is a bit more
+// complicated that it seems like it should be. First, we make everything "old": but
+// only a few seconds old, or it might be older than 6g (or the runtime source) and
+// everything will get rebuilt. Then define a timestamp slightly newer than this
+// time, which is what we set the mtime to of a file to cause it to be seen as new,
+// and finally another slightly even newer one that we can compare files against to
+// see if they have been rebuilt.
+var oldTime = time.Now().Add(-9 * time.Second)
+var nearlyNew = time.Now().Add(-6 * time.Second)
+var stampTime = time.Now().Add(-3 * time.Second)
+
+// resetFileStamps makes "everything" (bin, src, pkg from GOPATH and the
+// test-specific parts of GOROOT) appear old.
+func resetFileStamps() {
+	chtime := func(path string, info os.FileInfo, err error) error {
+		return os.Chtimes(path, oldTime, oldTime)
+	}
+	reset := func(path string) {
+		if err := filepath.Walk(path, chtime); err != nil {
+			log.Fatalf("resetFileStamps failed: %v", err)
+		}
+
+	}
+	reset("bin")
+	reset("pkg")
+	reset("src")
+	reset(gorootInstallDir)
+}
+
+// touch makes path newer than the "old" time stamp used by resetFileStamps.
+func touch(path string) {
+	if err := os.Chtimes(path, nearlyNew, nearlyNew); err != nil {
+		log.Fatalf("os.Chtimes failed: %v", err)
+	}
+}
+
+// isNew returns if the path is newer than the time stamp used by touch.
+func isNew(path string) bool {
+	fi, err := os.Stat(path)
+	if err != nil {
+		log.Fatalf("os.Stat failed: %v", err)
+	}
+	return fi.ModTime().After(stampTime)
+}
+
+// Fail unless path has been rebuilt (i.e. is newer than the time stamp used by
+// isNew)
+func AssertRebuilt(t *testing.T, msg, path string) {
+	if !isNew(path) {
+		t.Errorf("%s was not rebuilt (%s)", msg, path)
+	}
+}
+
+// Fail if path has been rebuilt (i.e. is newer than the time stamp used by isNew)
+func AssertNotRebuilt(t *testing.T, msg, path string) {
+	if isNew(path) {
+		t.Errorf("%s was rebuilt (%s)", msg, path)
+	}
+}
+
+func TestRebuilding(t *testing.T) {
+	goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+	goCmd(t, "install", "-linkshared", "exe")
+
+	// If the source is newer than both the .a file and the .so, both are rebuilt.
+	resetFileStamps()
+	touch("src/dep/dep.go")
+	goCmd(t, "install", "-linkshared", "exe")
+	AssertRebuilt(t, "new source", filepath.Join(gopathInstallDir, "dep.a"))
+	AssertRebuilt(t, "new source", filepath.Join(gopathInstallDir, "libdep.so"))
+
+	// If the .a file is newer than the .so, the .so is rebuilt (but not the .a)
+	resetFileStamps()
+	touch(filepath.Join(gopathInstallDir, "dep.a"))
+	goCmd(t, "install", "-linkshared", "exe")
+	AssertNotRebuilt(t, "new .a file", filepath.Join(gopathInstallDir, "dep.a"))
+	AssertRebuilt(t, "new .a file", filepath.Join(gopathInstallDir, "libdep.so"))
+}
+
+func appendFile(path, content string) {
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_APPEND, 0660)
+	if err != nil {
+		log.Fatalf("os.OpenFile failed: %v", err)
+	}
+	defer func() {
+		err := f.Close()
+		if err != nil {
+			log.Fatalf("f.Close failed: %v", err)
+		}
+	}()
+	_, err = f.WriteString(content)
+	if err != nil {
+		log.Fatalf("f.WriteString failed: %v", err)
+	}
+}
+
+func TestABIChecking(t *testing.T) {
+	goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+	goCmd(t, "install", "-linkshared", "exe")
+
+	// If we make an ABI-breaking change to dep and rebuild libp.so but not exe,
+	// exe will abort with a complaint on startup.
+	// This assumes adding an exported function breaks ABI, which is not true in
+	// some senses but suffices for the narrow definition of ABI compatiblity the
+	// toolchain uses today.
+	appendFile("src/dep/dep.go", "func ABIBreak() {}\n")
+	goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+	c := exec.Command("./bin/exe")
+	output, err := c.CombinedOutput()
+	if err == nil {
+		t.Fatal("executing exe did not fail after ABI break")
+	}
+	scanner := bufio.NewScanner(bytes.NewReader(output))
+	foundMsg := false
+	const wantLine = "abi mismatch detected between the executable and libdep.so"
+	for scanner.Scan() {
+		if scanner.Text() == wantLine {
+			foundMsg = true
+			break
+		}
+	}
+	if err = scanner.Err(); err != nil {
+		t.Errorf("scanner encountered error: %v", err)
+	}
+	if !foundMsg {
+		t.Fatalf("exe failed, but without line %q; got output:\n%s", wantLine, output)
+	}
+
+	// Rebuilding exe makes it work again.
+	goCmd(t, "install", "-linkshared", "exe")
+	run(t, "rebuilt exe", "./bin/exe")
+
+	// If we make a change which does not break ABI (such as adding an unexported
+	// function) and rebuild libdep.so, exe still works.
+	appendFile("src/dep/dep.go", "func noABIBreak() {}\n")
+	goCmd(t, "install", "-buildmode=shared", "-linkshared", "dep")
+	run(t, "after non-ABI breaking change", "./bin/exe")
+}