cmd/gomobile: reorganize build logic

The goal here is to remove several inconsistencies between
-target=android and -target=ios support, along with making the flow
of the command follow the path you might expect given a certain set
of flags, and preparing for `gomobile bind` support of ios. In
particular, building non-main packages now works with both targets
and the initialization of global build state is clearer.

The reorg also is designed around an nm trick I thought of
yesterday to do better package import scanning without a slow
all-file scan. This will give better detection of x/mobile/app and
x/mobile/exp/audio/al packages. There's a TODO about it, and I'll do
it in a future CL.

Tested with:

	go test golang.org/x/mobile/cmd/gomobile
	gomobile init
	gomobile bind golang.org/x/mobile/asset
	go test golang.org/x/mobile/bind/java
	gomobile build -target=ios golang.org/x/mobile/example/basic
	gomobile build -target=ios golang.org/x/mobile/gl
	gomobile build -target=android golang.org/x/mobile/gl
	gomobile build -target=android golang.org/x/mobile/example/basic
	(Along with manual testing of basic on an android device.)

That might make a pretty good _test.go.

Change-Id: I41230008c3c15db25a11c33b9eaca4abada9f411
Reviewed-on: https://go-review.googlesource.com/12051
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

bind/java/Seq.java

@@ -21,6 +21,7 @@ public class Seq {
 			Class.forName("go.LoadJNI");
 		} catch (ClassNotFoundException e) {
 			// Ignore, assume the user will load JNI for it.
+			Log.w("GoSeq", "LoadJNI class not found");
 		}
 
 		initSeq();
@@ -239,7 +240,7 @@ public class Seq {
 			if (refnum <= 0) {
 				// We don't keep track of the Go object.
 				// This must not happen.
-				Log.wtf("Seq", "dec request for Go object "+ refnum);
+				Log.wtf("GoSeq", "dec request for Go object "+ refnum);
 				return;
 			}
 			// Java objects are removed on request of Go.

cmd/gomobile/bind.go

@@ -5,8 +5,6 @@
 package main
 
 import (
-	"archive/zip"
-	"bytes"
 	"errors"
 	"fmt"
 	"go/ast"
@@ -17,11 +15,7 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
-	"strconv"
-	"strings"
-	"text/template"
 	"unicode"
 	"unicode/utf8"
 
@@ -30,7 +24,7 @@ import (
 	"golang.org/x/tools/go/types"
 )
 
-// ctx, pkg, ndkccpath, tmpdir in build.go
+// ctx, pkg, tmpdir in build.go
 
 var cmdBind = &command{
 	run:   runBind,
@@ -69,18 +63,20 @@ For documentation, see 'go help build'.
 }
 
 func runBind(cmd *command) error {
-	cwd, err := os.Getwd()
+	cleanup, err := envInit()
 	if err != nil {
-		panic(err)
+		return err
 	}
+	defer cleanup()
+
 	args := cmd.flag.Args()
 
-	var bindPkg *build.Package
+	var pkg *build.Package
 	switch len(args) {
 	case 0:
-		bindPkg, err = ctx.ImportDir(cwd, build.ImportComment)
+		pkg, err = ctx.ImportDir(cwd, build.ImportComment)
 	case 1:
-		bindPkg, err = ctx.Import(args[0], cwd, build.ImportComment)
+		pkg, err = ctx.Import(args[0], cwd, build.ImportComment)
 	default:
 		cmd.usage()
 		os.Exit(1)
@@ -91,89 +87,14 @@ func runBind(cmd *command) error {
 
 	switch buildTarget {
 	case "android":
-		// implementation is below
+		return goAndroidBind(pkg)
 	case "ios":
 		return fmt.Errorf(`-target=ios not yet supported`)
 	default:
 		return fmt.Errorf(`unknown -target, %q.`, buildTarget)
 	}
-
-	if sdkDir := os.Getenv("ANDROID_HOME"); sdkDir == "" {
-		return fmt.Errorf("this command requires ANDROID_HOME environment variable (path to the Android SDK)")
-	}
-
-	if buildN {
-		tmpdir = "$WORK"
-	} else {
-		tmpdir, err = ioutil.TempDir("", "gomobile-bind-work-")
-		if err != nil {
-			return err
-		}
-	}
-	defer removeAll(tmpdir)
-	if buildX {
-		fmt.Fprintln(os.Stderr, "WORK="+tmpdir)
-	}
-
-	binder, err := newBinder(bindPkg)
-	if err != nil {
-		return err
-	}
-
-	if err := binder.GenGo(tmpdir); err != nil {
-		return err
-	}
-
-	mainFile := filepath.Join(tmpdir, "androidlib/main.go")
-	err = writeFile(mainFile, func(w io.Writer) error {
-		return androidMainTmpl.Execute(w, "../go_"+binder.pkg.Name())
-	})
-	if err != nil {
-		return fmt.Errorf("failed to create the main package for android: %v", err)
-	}
-
-	androidDir := filepath.Join(tmpdir, "android")
-
-	err = goAndroidBuild(mainFile, filepath.Join(androidDir, "src/main/jniLibs/armeabi-v7a/libgojni.so"))
-	if err != nil {
-		return err
-	}
-
-	p, err := ctx.Import("golang.org/x/mobile/app", cwd, build.ImportComment)
-	if err != nil {
-		return fmt.Errorf(`"golang.org/x/mobile/app" is not found; run go get golang.org/x/mobile/app`)
-	}
-	repo := filepath.Clean(filepath.Join(p.Dir, "..")) // golang.org/x/mobile directory.
-
-	// TODO(crawshaw): use a better package path derived from the go package.
-	if err := binder.GenJava(filepath.Join(androidDir, "src/main/java/go/"+binder.pkg.Name())); err != nil {
-		return err
-	}
-
-	dst := filepath.Join(androidDir, "src/main/java/go/LoadJNI.java")
-	if err := ioutil.WriteFile(dst, []byte(loadSrc), 0664); err != nil {
-		return err
-	}
-
-	src := filepath.Join(repo, "bind/java/Seq.java")
-	dst = filepath.Join(androidDir, "src/main/java/go/Seq.java")
-	rm(dst)
-	if err := symlink(src, dst); err != nil {
-		return err
-	}
-
-	return buildAAR(androidDir, bindPkg)
 }
 
-var loadSrc = `package go;
-
-public class LoadJNI {
-	static {
-		System.loadLibrary("gojni");
-	}
-}
-`
-
 type binder struct {
 	files []*ast.File
 	fset  *token.FileSet
@@ -294,300 +215,3 @@ func newBinder(bindPkg *build.Package) (*binder, error) {
 	}
 	return b, nil
 }
-
-var androidMainTmpl = template.Must(template.New("android.go").Parse(`
-package main
-
-import (
-	_ "golang.org/x/mobile/bind/java"
-	_ "{{.}}"
-)
-
-func main() {}
-`))
-
-// AAR is the format for the binary distribution of an Android Library Project
-// and it is a ZIP archive with extension .aar.
-// http://tools.android.com/tech-docs/new-build-system/aar-format
-//
-// These entries are directly at the root of the archive.
-//
-//	AndroidManifest.xml (mandatory)
-// 	classes.jar (mandatory)
-//	assets/ (optional)
-//	jni/<abi>/libgojni.so
-//	R.txt (mandatory)
-//	res/ (mandatory)
-//	libs/*.jar (optional, not relevant)
-//	proguard.txt (optional)
-//	lint.jar (optional, not relevant)
-//	aidl (optional, not relevant)
-//
-// javac and jar commands are needed to build classes.jar.
-func buildAAR(androidDir string, pkg *build.Package) (err error) {
-	var out io.Writer = ioutil.Discard
-	if buildO == "" {
-		buildO = pkg.Name + ".aar"
-	}
-	if !strings.HasSuffix(buildO, ".aar") {
-		return fmt.Errorf("output file name %q does not end in '.aar'", buildO)
-	}
-	if !buildN {
-		f, err := os.Create(buildO)
-		if err != nil {
-			return err
-		}
-		defer func() {
-			if cerr := f.Close(); err == nil {
-				err = cerr
-			}
-		}()
-		out = f
-	}
-
-	aarw := zip.NewWriter(out)
-	aarwcreate := func(name string) (io.Writer, error) {
-		if buildV {
-			fmt.Fprintf(os.Stderr, "aar: %s\n", name)
-		}
-		return aarw.Create(name)
-	}
-	w, err := aarwcreate("AndroidManifest.xml")
-	if err != nil {
-		return err
-	}
-	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q />`
-	fmt.Fprintf(w, manifestFmt, "go."+pkg.Name+".gojni")
-
-	w, err = aarwcreate("proguard.txt")
-	if err != nil {
-		return err
-	}
-	fmt.Fprintln(w, `-keep class go.** { *; }`)
-
-	w, err = aarwcreate("classes.jar")
-	if err != nil {
-		return err
-	}
-	src := filepath.Join(androidDir, "src/main/java")
-	if err := buildJar(w, src); err != nil {
-		return err
-	}
-
-	assetsDir := filepath.Join(pkg.Dir, "assets")
-	assetsDirExists := false
-	if fi, err := os.Stat(assetsDir); err == nil {
-		assetsDirExists = fi.IsDir()
-	} else if !os.IsNotExist(err) {
-		return err
-	}
-
-	if assetsDirExists {
-		err := filepath.Walk(
-			assetsDir, func(path string, info os.FileInfo, err error) error {
-				if err != nil {
-					return err
-				}
-				if info.IsDir() {
-					return nil
-				}
-				f, err := os.Open(path)
-				if err != nil {
-					return err
-				}
-				defer f.Close()
-				name := "assets/" + path[len(assetsDir)+1:]
-				w, err := aarwcreate(name)
-				if err != nil {
-					return nil
-				}
-				_, err = io.Copy(w, f)
-				return err
-			})
-		if err != nil {
-			return err
-		}
-	}
-
-	lib := "armeabi-v7a/libgojni.so"
-	w, err = aarwcreate("jni/" + lib)
-	if err != nil {
-		return err
-	}
-	if !buildN {
-		r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
-		if err != nil {
-			return err
-		}
-		defer r.Close()
-		if _, err := io.Copy(w, r); err != nil {
-			return err
-		}
-	}
-
-	// TODO(hyangah): do we need to use aapt to create R.txt?
-	w, err = aarwcreate("R.txt")
-	if err != nil {
-		return err
-	}
-
-	w, err = aarwcreate("res/")
-	if err != nil {
-		return err
-	}
-
-	return aarw.Close()
-}
-
-const (
-	javacTargetVer = "1.7"
-	minAndroidAPI  = 9
-)
-
-func buildJar(w io.Writer, srcDir string) error {
-	var srcFiles []string
-	if buildN {
-		srcFiles = []string{"*.java"}
-	} else {
-		err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
-			if err != nil {
-				return err
-			}
-			if filepath.Ext(path) == ".java" {
-				srcFiles = append(srcFiles, filepath.Join(".", path[len(srcDir):]))
-			}
-			return nil
-		})
-		if err != nil {
-			return err
-		}
-	}
-
-	dst := filepath.Join(tmpdir, "javac-output")
-	if !buildN {
-		if err := os.MkdirAll(dst, 0700); err != nil {
-			return err
-		}
-	}
-	defer removeAll(dst)
-
-	apiPath, err := androidAPIPath()
-	if err != nil {
-		return err
-	}
-
-	args := []string{
-		"-d", dst,
-		"-source", javacTargetVer,
-		"-target", javacTargetVer,
-		"-bootclasspath", filepath.Join(apiPath, "android.jar"),
-	}
-	args = append(args, srcFiles...)
-
-	buf := new(bytes.Buffer)
-	javac := exec.Command("javac", args...)
-	javac.Dir = srcDir
-	if buildV {
-		javac.Stdout = os.Stdout
-		javac.Stderr = os.Stderr
-	} else {
-		javac.Stdout = buf
-		javac.Stderr = buf
-	}
-	if buildX {
-		printcmd("%s", strings.Join(javac.Args, " "))
-	}
-	if !buildN {
-		if err := javac.Run(); err != nil {
-			buf.WriteTo(xout)
-			return err
-		}
-	}
-
-	if buildX {
-		printcmd("jar c -C %s .", dst)
-	}
-	if buildN {
-		return nil
-	}
-
-	jarw := zip.NewWriter(w)
-	jarwcreate := func(name string) (io.Writer, error) {
-		if buildV {
-			fmt.Fprintf(os.Stderr, "jar: %s\n", name)
-		}
-		return jarw.Create(name)
-	}
-	f, err := jarwcreate("META-INF/MANIFEST.MF")
-	if err != nil {
-		return err
-	}
-	fmt.Fprintf(f, manifestHeader)
-
-	err = filepath.Walk(dst, func(path string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
-		if info.IsDir() {
-			return nil
-		}
-		out, err := jarwcreate(filepath.ToSlash(path[len(dst)+1:]))
-		if err != nil {
-			return err
-		}
-		in, err := os.Open(path)
-		if err != nil {
-			return err
-		}
-		defer in.Close()
-		_, err = io.Copy(out, in)
-		return err
-	})
-	if err != nil {
-		return err
-	}
-	return jarw.Close()
-}
-
-// androidAPIPath returns an android SDK platform directory under ANDROID_HOME.
-// If there are multiple platforms that satisfy the minimum version requirement
-// androidAPIPath returns the latest one among them.
-func androidAPIPath() (string, error) {
-	sdk := os.Getenv("ANDROID_HOME")
-	if sdk == "" {
-		return "", fmt.Errorf("ANDROID_HOME environment var is not set")
-	}
-	sdkDir, err := os.Open(filepath.Join(sdk, "platforms"))
-	if err != nil {
-		return "", fmt.Errorf("failed to find android SDK platform: %v", err)
-	}
-	defer sdkDir.Close()
-	fis, err := sdkDir.Readdir(-1)
-	if err != nil {
-		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d): %v", minAndroidAPI, err)
-	}
-
-	var apiPath string
-	var apiVer int
-	for _, fi := range fis {
-		name := fi.Name()
-		if !fi.IsDir() || !strings.HasPrefix(name, "android-") {
-			continue
-		}
-		n, err := strconv.Atoi(name[len("android-"):])
-		if err != nil || n < minAndroidAPI {
-			continue
-		}
-		p := filepath.Join(sdkDir.Name(), name)
-		_, err = os.Stat(filepath.Join(p, "android.jar"))
-		if err == nil && apiVer < n {
-			apiPath = p
-			apiVer = n
-		}
-	}
-	if apiVer == 0 {
-		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d) in %s",
-			minAndroidAPI, sdkDir.Name())
-	}
-	return apiPath, nil
-}

cmd/gomobile/bind_androidapp.go

@@ -0,0 +1,386 @@
+// 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 main
+
+import (
+	"archive/zip"
+	"bytes"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"text/template"
+)
+
+func goAndroidBind(pkg *build.Package) error {
+	if sdkDir := os.Getenv("ANDROID_HOME"); sdkDir == "" {
+		return fmt.Errorf("this command requires ANDROID_HOME environment variable (path to the Android SDK)")
+	}
+
+	binder, err := newBinder(pkg)
+	if err != nil {
+		return err
+	}
+
+	if err := binder.GenGo(tmpdir); err != nil {
+		return err
+	}
+
+	mainFile := filepath.Join(tmpdir, "androidlib/main.go")
+	err = writeFile(mainFile, func(w io.Writer) error {
+		return androidMainTmpl.Execute(w, "../go_"+binder.pkg.Name())
+	})
+	if err != nil {
+		return fmt.Errorf("failed to create the main package for android: %v", err)
+	}
+
+	androidDir := filepath.Join(tmpdir, "android")
+
+	err = goBuild(
+		mainFile,
+		androidArmEnv,
+		"-buildmode=c-shared",
+		"-o="+filepath.Join(androidDir, "src/main/jniLibs/armeabi-v7a/libgojni.so"),
+	)
+	if err != nil {
+		return err
+	}
+
+	p, err := ctx.Import("golang.org/x/mobile/bind", cwd, build.ImportComment)
+	if err != nil {
+		return fmt.Errorf(`"golang.org/x/mobile/bind" is not found; run go get golang.org/x/mobile/bind`)
+	}
+	repo := filepath.Clean(filepath.Join(p.Dir, "..")) // golang.org/x/mobile directory.
+
+	// TODO(crawshaw): use a better package path derived from the go package.
+	if err := binder.GenJava(filepath.Join(androidDir, "src/main/java/go/"+binder.pkg.Name())); err != nil {
+		return err
+	}
+
+	dst := filepath.Join(androidDir, "src/main/java/go/LoadJNI.java")
+	if err := ioutil.WriteFile(dst, []byte(loadSrc), 0664); err != nil {
+		return err
+	}
+
+	src := filepath.Join(repo, "bind/java/Seq.java")
+	dst = filepath.Join(androidDir, "src/main/java/go/Seq.java")
+	rm(dst)
+	if err := symlink(src, dst); err != nil {
+		return err
+	}
+
+	return buildAAR(androidDir, pkg)
+}
+
+var loadSrc = `package go;
+
+public class LoadJNI {
+	static {
+		System.loadLibrary("gojni");
+	}
+}
+`
+
+var androidMainTmpl = template.Must(template.New("android.go").Parse(`
+package main
+
+import (
+	_ "golang.org/x/mobile/bind/java"
+	_ "{{.}}"
+)
+
+func main() {}
+`))
+
+// AAR is the format for the binary distribution of an Android Library Project
+// and it is a ZIP archive with extension .aar.
+// http://tools.android.com/tech-docs/new-build-system/aar-format
+//
+// These entries are directly at the root of the archive.
+//
+//	AndroidManifest.xml (mandatory)
+// 	classes.jar (mandatory)
+//	assets/ (optional)
+//	jni/<abi>/libgojni.so
+//	R.txt (mandatory)
+//	res/ (mandatory)
+//	libs/*.jar (optional, not relevant)
+//	proguard.txt (optional)
+//	lint.jar (optional, not relevant)
+//	aidl (optional, not relevant)
+//
+// javac and jar commands are needed to build classes.jar.
+func buildAAR(androidDir string, pkg *build.Package) (err error) {
+	var out io.Writer = ioutil.Discard
+	if buildO == "" {
+		buildO = pkg.Name + ".aar"
+	}
+	if !strings.HasSuffix(buildO, ".aar") {
+		return fmt.Errorf("output file name %q does not end in '.aar'", buildO)
+	}
+	if !buildN {
+		f, err := os.Create(buildO)
+		if err != nil {
+			return err
+		}
+		defer func() {
+			if cerr := f.Close(); err == nil {
+				err = cerr
+			}
+		}()
+		out = f
+	}
+
+	aarw := zip.NewWriter(out)
+	aarwcreate := func(name string) (io.Writer, error) {
+		if buildV {
+			fmt.Fprintf(os.Stderr, "aar: %s\n", name)
+		}
+		return aarw.Create(name)
+	}
+	w, err := aarwcreate("AndroidManifest.xml")
+	if err != nil {
+		return err
+	}
+	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q />`
+	fmt.Fprintf(w, manifestFmt, "go."+pkg.Name+".gojni")
+
+	w, err = aarwcreate("proguard.txt")
+	if err != nil {
+		return err
+	}
+	fmt.Fprintln(w, `-keep class go.** { *; }`)
+
+	w, err = aarwcreate("classes.jar")
+	if err != nil {
+		return err
+	}
+	src := filepath.Join(androidDir, "src/main/java")
+	if err := buildJar(w, src); err != nil {
+		return err
+	}
+
+	assetsDir := filepath.Join(pkg.Dir, "assets")
+	assetsDirExists := false
+	if fi, err := os.Stat(assetsDir); err == nil {
+		assetsDirExists = fi.IsDir()
+	} else if !os.IsNotExist(err) {
+		return err
+	}
+
+	if assetsDirExists {
+		err := filepath.Walk(
+			assetsDir, func(path string, info os.FileInfo, err error) error {
+				if err != nil {
+					return err
+				}
+				if info.IsDir() {
+					return nil
+				}
+				f, err := os.Open(path)
+				if err != nil {
+					return err
+				}
+				defer f.Close()
+				name := "assets/" + path[len(assetsDir)+1:]
+				w, err := aarwcreate(name)
+				if err != nil {
+					return nil
+				}
+				_, err = io.Copy(w, f)
+				return err
+			})
+		if err != nil {
+			return err
+		}
+	}
+
+	lib := "armeabi-v7a/libgojni.so"
+	w, err = aarwcreate("jni/" + lib)
+	if err != nil {
+		return err
+	}
+	if !buildN {
+		r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
+		if err != nil {
+			return err
+		}
+		defer r.Close()
+		if _, err := io.Copy(w, r); err != nil {
+			return err
+		}
+	}
+
+	// TODO(hyangah): do we need to use aapt to create R.txt?
+	w, err = aarwcreate("R.txt")
+	if err != nil {
+		return err
+	}
+
+	w, err = aarwcreate("res/")
+	if err != nil {
+		return err
+	}
+
+	return aarw.Close()
+}
+
+const (
+	javacTargetVer = "1.7"
+	minAndroidAPI  = 9
+)
+
+func buildJar(w io.Writer, srcDir string) error {
+	var srcFiles []string
+	if buildN {
+		srcFiles = []string{"*.java"}
+	} else {
+		err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			if filepath.Ext(path) == ".java" {
+				srcFiles = append(srcFiles, filepath.Join(".", path[len(srcDir):]))
+			}
+			return nil
+		})
+		if err != nil {
+			return err
+		}
+	}
+
+	dst := filepath.Join(tmpdir, "javac-output")
+	if !buildN {
+		if err := os.MkdirAll(dst, 0700); err != nil {
+			return err
+		}
+	}
+	defer removeAll(dst)
+
+	apiPath, err := androidAPIPath()
+	if err != nil {
+		return err
+	}
+
+	args := []string{
+		"-d", dst,
+		"-source", javacTargetVer,
+		"-target", javacTargetVer,
+		"-bootclasspath", filepath.Join(apiPath, "android.jar"),
+	}
+	args = append(args, srcFiles...)
+
+	buf := new(bytes.Buffer)
+	javac := exec.Command("javac", args...)
+	javac.Dir = srcDir
+	if buildV {
+		javac.Stdout = os.Stdout
+		javac.Stderr = os.Stderr
+	} else {
+		javac.Stdout = buf
+		javac.Stderr = buf
+	}
+	if buildX {
+		printcmd("%s", strings.Join(javac.Args, " "))
+	}
+	if !buildN {
+		if err := javac.Run(); err != nil {
+			buf.WriteTo(xout)
+			return err
+		}
+	}
+
+	if buildX {
+		printcmd("jar c -C %s .", dst)
+	}
+	if buildN {
+		return nil
+	}
+
+	jarw := zip.NewWriter(w)
+	jarwcreate := func(name string) (io.Writer, error) {
+		if buildV {
+			fmt.Fprintf(os.Stderr, "jar: %s\n", name)
+		}
+		return jarw.Create(name)
+	}
+	f, err := jarwcreate("META-INF/MANIFEST.MF")
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(f, manifestHeader)
+
+	err = filepath.Walk(dst, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+		out, err := jarwcreate(filepath.ToSlash(path[len(dst)+1:]))
+		if err != nil {
+			return err
+		}
+		in, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer in.Close()
+		_, err = io.Copy(out, in)
+		return err
+	})
+	if err != nil {
+		return err
+	}
+	return jarw.Close()
+}
+
+// androidAPIPath returns an android SDK platform directory under ANDROID_HOME.
+// If there are multiple platforms that satisfy the minimum version requirement
+// androidAPIPath returns the latest one among them.
+func androidAPIPath() (string, error) {
+	sdk := os.Getenv("ANDROID_HOME")
+	if sdk == "" {
+		return "", fmt.Errorf("ANDROID_HOME environment var is not set")
+	}
+	sdkDir, err := os.Open(filepath.Join(sdk, "platforms"))
+	if err != nil {
+		return "", fmt.Errorf("failed to find android SDK platform: %v", err)
+	}
+	defer sdkDir.Close()
+	fis, err := sdkDir.Readdir(-1)
+	if err != nil {
+		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d): %v", minAndroidAPI, err)
+	}
+
+	var apiPath string
+	var apiVer int
+	for _, fi := range fis {
+		name := fi.Name()
+		if !fi.IsDir() || !strings.HasPrefix(name, "android-") {
+			continue
+		}
+		n, err := strconv.Atoi(name[len("android-"):])
+		if err != nil || n < minAndroidAPI {
+			continue
+		}
+		p := filepath.Join(sdkDir.Name(), name)
+		_, err = os.Stat(filepath.Join(p, "android.jar"))
+		if err == nil && apiVer < n {
+			apiPath = p
+			apiVer = n
+		}
+	}
+	if apiVer == 0 {
+		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d) in %s",
+			minAndroidAPI, sdkDir.Name())
+	}
+	return apiPath, nil
+}

cmd/gomobile/build.go

@@ -6,26 +6,18 @@ package main
 
 import (
 	"bytes"
-	"crypto/x509"
-	"encoding/pem"
-	"errors"
 	"fmt"
 	"go/build"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
-	"path"
-	"path/filepath"
 	"runtime"
 	"strconv"
 	"strings"
 )
 
 var ctx = build.Default
-var pkg *build.Package
+var pkg *build.Package // TODO(crawshaw): remove global pkg variable
-var gomobilepath string // $GOPATH/pkg/gomobile
-var ndkccpath string    // $GOPATH/pkg/gomobile/android-{{.NDK}}
 var tmpdir string
 
 var cmdBuild = &command{
@@ -62,10 +54,12 @@ For documentation, see 'go help build'.
 }
 
 func runBuild(cmd *command) (err error) {
-	cwd, err := os.Getwd()
+	cleanup, err := envInit()
 	if err != nil {
-		panic(err)
+		return err
 	}
+	defer cleanup()
+
 	args := cmd.flag.Args()
 
 	switch len(args) {
@@ -81,214 +75,43 @@ func runBuild(cmd *command) (err error) {
 		return err
 	}
 
+	if pkg.Name != "main" && buildO != "" {
+		return fmt.Errorf("cannot set -o when building non-main package")
+	}
+
 	switch buildTarget {
 	case "android":
-		// implementation is below
+		if pkg.Name != "main" {
+			return goBuild(pkg.ImportPath, androidArmEnv)
+		}
+		if err := goAndroidBuild(pkg); err != nil {
+			return err
+		}
 	case "ios":
-		if runtime.GOOS == "darwin" {
+		if runtime.GOOS != "darwin" {
-			if pkg.Name != "main" {
+			return fmt.Errorf("-target=ios requires darwin host")
-				return fmt.Errorf("cannot build non-main packages")
+		}
-			}
+		if pkg.Name != "main" {
-			if err := importsApp(pkg); err != nil {
+			if err := goBuild(pkg.ImportPath, darwinArmEnv); err != nil {
 				return err
 			}
-			return goIOSBuild(pkg.ImportPath)
+			return goBuild(pkg.ImportPath, darwinArm64Env)
+		}
+		if err := goIOSBuild(pkg); err != nil {
+			return err
 		}
-		return fmt.Errorf("-target=ios requires darwin host")
 	default:
 		return fmt.Errorf(`unknown -target, %q.`, buildTarget)
 	}
 
-	if pkg.Name != "main" {
+	// TODO(crawshaw): This is an incomplete package scan.
-		// Not an app, don't build a final package.
+	// A complete package scan would be too expensive. Instead,
-		return goAndroidBuild(pkg.ImportPath, "")
+	// fake it. After the binary is built, scan its symbols
-	}
+	// with nm and look for the app and al packages.
-
 	if err := importsApp(pkg); err != nil {
 		return err
 	}
 
-	if buildN {
-		tmpdir = "$WORK"
-	} else {
-		tmpdir, err = ioutil.TempDir("", "gobuildapk-work-")
-		if err != nil {
-			return err
-		}
-	}
-	defer removeAll(tmpdir)
-	if buildX {
-		fmt.Fprintln(xout, "WORK="+tmpdir)
-	}
-
-	libName := path.Base(pkg.ImportPath)
-	manifestData, err := ioutil.ReadFile(filepath.Join(pkg.Dir, "AndroidManifest.xml"))
-	if err != nil {
-		if !os.IsNotExist(err) {
-			return err
-		}
-		buf := new(bytes.Buffer)
-		buf.WriteString(`<?xml version="1.0" encoding="utf-8"?>`)
-		err := manifestTmpl.Execute(buf, manifestTmplData{
-			// TODO(crawshaw): a better package path.
-			JavaPkgPath: "org.golang.todo." + libName,
-			Name:        libName,
-			LibName:     libName,
-		})
-		if err != nil {
-			return err
-		}
-		manifestData = buf.Bytes()
-		if buildV {
-			fmt.Fprintf(os.Stderr, "generated AndroidManifest.xml:\n%s\n", manifestData)
-		}
-	} else {
-		libName, err = manifestLibName(manifestData)
-		if err != nil {
-			return err
-		}
-	}
-	libPath := filepath.Join(tmpdir, "lib"+libName+".so")
-
-	if err := goAndroidBuild(pkg.ImportPath, libPath); err != nil {
-		return err
-	}
-	block, _ := pem.Decode([]byte(debugCert))
-	if block == nil {
-		return errors.New("no debug cert")
-	}
-	privKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
-	if err != nil {
-		return err
-	}
-
-	if buildO == "" {
-		buildO = filepath.Base(pkg.Dir) + ".apk"
-	}
-	if !strings.HasSuffix(buildO, ".apk") {
-		return fmt.Errorf("output file name %q does not end in '.apk'", buildO)
-	}
-	var out io.Writer
-	if !buildN {
-		f, err := os.Create(buildO)
-		if err != nil {
-			return err
-		}
-		defer func() {
-			if cerr := f.Close(); err == nil {
-				err = cerr
-			}
-		}()
-		out = f
-	}
-
-	var apkw *Writer
-	if !buildN {
-		apkw = NewWriter(out, privKey)
-	}
-	apkwcreate := func(name string) (io.Writer, error) {
-		if buildV {
-			fmt.Fprintf(os.Stderr, "apk: %s\n", name)
-		}
-		if buildN {
-			return ioutil.Discard, nil
-		}
-		return apkw.Create(name)
-	}
-
-	w, err := apkwcreate("AndroidManifest.xml")
-	if err != nil {
-		return err
-	}
-	if _, err := w.Write(manifestData); err != nil {
-		return err
-	}
-
-	w, err = apkwcreate("lib/armeabi/lib" + libName + ".so")
-	if err != nil {
-		return err
-	}
-	if !buildN {
-		r, err := os.Open(libPath)
-		if err != nil {
-			return err
-		}
-		if _, err := io.Copy(w, r); err != nil {
-			return err
-		}
-	}
-
-	importsAL := pkgImportsAL(pkg)
-	if importsAL {
-		alDir := filepath.Join(ndkccpath, "openal/lib")
-		filepath.Walk(alDir, func(path string, info os.FileInfo, err error) error {
-			if err != nil {
-				return err
-			}
-			if info.IsDir() {
-				return nil
-			}
-			name := "lib/" + path[len(alDir)+1:]
-			w, err := apkwcreate(name)
-			if err != nil {
-				return err
-			}
-			if !buildN {
-				f, err := os.Open(path)
-				if err != nil {
-					return err
-				}
-				defer f.Close()
-				_, err = io.Copy(w, f)
-			}
-			return err
-		})
-	}
-
-	// Add any assets.
-	assetsDir := filepath.Join(pkg.Dir, "assets")
-	assetsDirExists := true
-	fi, err := os.Stat(assetsDir)
-	if err != nil {
-		if os.IsNotExist(err) {
-			assetsDirExists = false
-		} else {
-			return err
-		}
-	} else {
-		assetsDirExists = fi.IsDir()
-	}
-	if assetsDirExists {
-		filepath.Walk(assetsDir, func(path string, info os.FileInfo, err error) error {
-			if err != nil {
-				return err
-			}
-			if info.IsDir() {
-				return nil
-			}
-			name := "assets/" + path[len(assetsDir)+1:]
-			w, err := apkwcreate(name)
-			if err != nil {
-				return err
-			}
-			f, err := os.Open(path)
-			if err != nil {
-				return err
-			}
-			defer f.Close()
-			_, err = io.Copy(w, f)
-			return err
-		})
-	}
-
-	// TODO: add gdbserver to apk?
-
-	if !buildN {
-		if err := apkw.Close(); err != nil {
-			return err
-		}
-	}
-
 	return nil
 }
 
@@ -353,114 +176,9 @@ func addBuildFlagsNVX(cmd *command) {
 	cmd.flag.BoolVar(&buildX, "x", false, "")
 }
 
-// goAndroidBuild builds a package.
+type binInfo struct {
-// If libPath is specified then it builds as a shared library.
+	hasPkgApp bool
-func goAndroidBuild(src, libPath string) error {
+	hasPkgAL  bool
-	version, err := goVersion()
-	if err != nil {
-		return err
-	}
-
-	gopath := goEnv("GOPATH")
-	for _, p := range filepath.SplitList(gopath) {
-		gomobilepath = filepath.Join(p, "pkg", "gomobile")
-		if _, err = os.Stat(gomobilepath); err == nil {
-			break
-		}
-	}
-	if err != nil || gomobilepath == "" {
-		return errors.New("toolchain not installed, run:\n\tgomobile init")
-	}
-	verpath := filepath.Join(gomobilepath, "version")
-	installedVersion, err := ioutil.ReadFile(verpath)
-	if err != nil {
-		return errors.New("toolchain partially installed, run:\n\tgomobile init")
-	}
-	if !bytes.Equal(installedVersion, version) {
-		return errors.New("toolchain out of date, run:\n\tgomobile init")
-	}
-
-	ndkccpath = filepath.Join(gomobilepath, "android-"+ndkVersion)
-	ndkccbin := filepath.Join(ndkccpath, "arm", "bin")
-	if buildX {
-		fmt.Fprintln(xout, "GOMOBILE="+gomobilepath)
-	}
-
-	gocmd := exec.Command(
-		`go`,
-		`build`,
-		`-tags=`+strconv.Quote(strings.Join(ctx.BuildTags, ",")),
-	)
-	if buildV {
-		gocmd.Args = append(gocmd.Args, "-v")
-	}
-	if buildI {
-		gocmd.Args = append(gocmd.Args, "-i")
-	}
-	if buildX {
-		gocmd.Args = append(gocmd.Args, "-x")
-	}
-	if libPath == "" {
-		if buildO != "" {
-			gocmd.Args = append(gocmd.Args, `-o`, buildO)
-		}
-	} else {
-		gocmd.Args = append(gocmd.Args, "-buildmode=c-shared", "-o", libPath)
-	}
-
-	gocmd.Args = append(gocmd.Args, src)
-
-	gocmd.Stdout = os.Stdout
-	gocmd.Stderr = os.Stderr
-	gocmd.Env = []string{
-		`GOOS=android`,
-		`GOARCH=arm`,
-		`GOARM=7`,
-		`CGO_ENABLED=1`,
-		`CC=` + filepath.Join(ndkccbin, "arm-linux-androideabi-gcc"),
-		`CXX=` + filepath.Join(ndkccbin, "arm-linux-androideabi-g++"),
-		`GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0"`,
-		`GOROOT=` + goEnv("GOROOT"),
-		`GOPATH=` + gopath,
-	}
-	if buildX {
-		printcmd("%s", strings.Join(gocmd.Env, " ")+" "+strings.Join(gocmd.Args, " "))
-	}
-	if !buildN {
-		gocmd.Env = environ(gocmd.Env)
-		if err := gocmd.Run(); err != nil {
-			return err
-		}
-	}
-	return nil
-}
-
-var importsALPkg = make(map[string]struct{})
-
-// pkgImportsAL returns true if the given package or one of its
-// dependencies imports the x/mobile/exp/audio/al package.
-func pkgImportsAL(pkg *build.Package) bool {
-	for _, path := range pkg.Imports {
-		if path == "C" {
-			continue
-		}
-		if _, ok := importsALPkg[path]; ok {
-			continue
-		}
-		importsALPkg[path] = struct{}{}
-		if strings.HasPrefix(path, "golang.org/x/mobile/exp/audio/al") {
-			return true
-		}
-		dPkg, err := ctx.Import(path, "", build.ImportComment)
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "error reading OpenAL library: %v", err)
-			os.Exit(2)
-		}
-		if pkgImportsAL(dPkg) {
-			return true
-		}
-	}
-	return false
 }
 
 func init() {
@@ -476,38 +194,6 @@ func init() {
 	addBuildFlagsNVX(cmdBind)
 }
 
-// A random uninteresting private key.
-// Must be consistent across builds so newer app versions can be installed.
-const debugCert = `
------BEGIN RSA PRIVATE KEY-----
-MIIEowIBAAKCAQEAy6ItnWZJ8DpX9R5FdWbS9Kr1U8Z7mKgqNByGU7No99JUnmyu
-NQ6Uy6Nj0Gz3o3c0BXESECblOC13WdzjsH1Pi7/L9QV8jXOXX8cvkG5SJAyj6hcO
-LOapjDiN89NXjXtyv206JWYvRtpexyVrmHJgRAw3fiFI+m4g4Qop1CxcIF/EgYh7
-rYrqh4wbCM1OGaCleQWaOCXxZGm+J5YNKQcWpjZRrDrb35IZmlT0bK46CXUKvCqK
-x7YXHgfhC8ZsXCtsScKJVHs7gEsNxz7A0XoibFw6DoxtjKzUCktnT0w3wxdY7OTj
-9AR8mobFlM9W3yirX8TtwekWhDNTYEu8dwwykwIDAQABAoIBAA2hjpIhvcNR9H9Z
-BmdEecydAQ0ZlT5zy1dvrWI++UDVmIp+Ve8BSd6T0mOqV61elmHi3sWsBN4M1Rdz
-3N38lW2SajG9q0fAvBpSOBHgAKmfGv3Ziz5gNmtHgeEXfZ3f7J95zVGhlHqWtY95
-JsmuplkHxFMyITN6WcMWrhQg4A3enKLhJLlaGLJf9PeBrvVxHR1/txrfENd2iJBH
-FmxVGILL09fIIktJvoScbzVOneeWXj5vJGzWVhB17DHBbANGvVPdD5f+k/s5aooh
-hWAy/yLKocr294C4J+gkO5h2zjjjSGcmVHfrhlXQoEPX+iW1TGoF8BMtl4Llc+jw
-lKWKfpECgYEA9C428Z6CvAn+KJ2yhbAtuRo41kkOVoiQPtlPeRYs91Pq4+NBlfKO
-2nWLkyavVrLx4YQeCeaEU2Xoieo9msfLZGTVxgRlztylOUR+zz2FzDBYGicuUD3s
-EqC0Wv7tiX6dumpWyOcVVLmR9aKlOUzA9xemzIsWUwL3PpyONhKSq7kCgYEA1X2F
-f2jKjoOVzglhtuX4/SP9GxS4gRf9rOQ1Q8DzZhyH2LZ6Dnb1uEQvGhiqJTU8CXxb
-7odI0fgyNXq425Nlxc1Tu0G38TtJhwrx7HWHuFcbI/QpRtDYLWil8Zr7Q3BT9rdh
-moo4m937hLMvqOG9pyIbyjOEPK2WBCtKW5yabqsCgYEAu9DkUBr1Qf+Jr+IEU9I8
-iRkDSMeusJ6gHMd32pJVCfRRQvIlG1oTyTMKpafmzBAd/rFpjYHynFdRcutqcShm
-aJUq3QG68U9EAvWNeIhA5tr0mUEz3WKTt4xGzYsyWES8u4tZr3QXMzD9dOuinJ1N
-+4EEumXtSPKKDG3M8Qh+KnkCgYBUEVSTYmF5EynXc2xOCGsuy5AsrNEmzJqxDUBI
-SN/P0uZPmTOhJIkIIZlmrlW5xye4GIde+1jajeC/nG7U0EsgRAV31J4pWQ5QJigz
-0+g419wxIUFryGuIHhBSfpP472+w1G+T2mAGSLh1fdYDq7jx6oWE7xpghn5vb9id
-EKLjdwKBgBtz9mzbzutIfAW0Y8F23T60nKvQ0gibE92rnUbjPnw8HjL3AZLU05N+
-cSL5bhq0N5XHK77sscxW9vXjG0LJMXmFZPp9F6aV6ejkMIXyJ/Yz/EqeaJFwilTq
-Mc6xR47qkdzu0dQ1aPm4XD7AWDtIvPo/GG2DKOucLBbQc2cOWtKS
------END RSA PRIVATE KEY-----
-`
-
 // environ merges os.Environ and the given "key=value" pairs.
 func environ(kv []string) []string {
 	envs := map[string]string{}
@@ -542,3 +228,48 @@ func environ(kv []string) []string {
 	}
 	return new
 }
+
+func goBuild(src string, env []string, args ...string) error {
+	cmd := exec.Command(
+		`go`,
+		`build`,
+		`-tags=`+strconv.Quote(strings.Join(ctx.BuildTags, ",")),
+	)
+	if buildV {
+		cmd.Args = append(cmd.Args, "-v")
+	}
+	if buildI {
+		cmd.Args = append(cmd.Args, "-i")
+	}
+	if buildX {
+		cmd.Args = append(cmd.Args, "-x")
+	}
+	cmd.Args = append(cmd.Args, args...)
+	cmd.Args = append(cmd.Args, src)
+	cmd.Env = append(cmd.Env, env...)
+	cmd.Env = append(cmd.Env,
+		`CGO_ENABLED=1`,
+		`GOROOT=`+goEnv("GOROOT"),
+		`GOPATH=`+goEnv("GOPATH"),
+	)
+	buf := new(bytes.Buffer)
+	buf.WriteByte('\n')
+	if buildV {
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+	} else {
+		cmd.Stdout = buf
+		cmd.Stderr = buf
+	}
+
+	if buildX {
+		printcmd("%s", strings.Join(cmd.Env, " ")+" "+strings.Join(cmd.Args, " "))
+	}
+	if !buildN {
+		cmd.Env = environ(cmd.Env)
+		if err := cmd.Run(); err != nil {
+			return fmt.Errorf("go build failed: %v%s", err, buf)
+		}
+	}
+	return nil
+}

cmd/gomobile/build_androidapp.go

@@ -0,0 +1,260 @@
+// 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 main
+
+import (
+	"bytes"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+func goAndroidBuild(pkg *build.Package) error {
+	libName := path.Base(pkg.ImportPath)
+	manifestData, err := ioutil.ReadFile(filepath.Join(pkg.Dir, "AndroidManifest.xml"))
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return err
+		}
+		buf := new(bytes.Buffer)
+		buf.WriteString(`<?xml version="1.0" encoding="utf-8"?>`)
+		err := manifestTmpl.Execute(buf, manifestTmplData{
+			// TODO(crawshaw): a better package path.
+			JavaPkgPath: "org.golang.todo." + libName,
+			Name:        libName,
+			LibName:     libName,
+		})
+		if err != nil {
+			return err
+		}
+		manifestData = buf.Bytes()
+		if buildV {
+			fmt.Fprintf(os.Stderr, "generated AndroidManifest.xml:\n%s\n", manifestData)
+		}
+	} else {
+		libName, err = manifestLibName(manifestData)
+		if err != nil {
+			return err
+		}
+	}
+	libPath := filepath.Join(tmpdir, "lib"+libName+".so")
+
+	err = goBuild(
+		pkg.ImportPath,
+		androidArmEnv,
+		"-buildmode=c-shared",
+		"-o", libPath,
+	)
+	if err != nil {
+		return err
+	}
+	block, _ := pem.Decode([]byte(debugCert))
+	if block == nil {
+		return errors.New("no debug cert")
+	}
+	privKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return err
+	}
+
+	if buildO == "" {
+		buildO = filepath.Base(pkg.Dir) + ".apk"
+	}
+	if !strings.HasSuffix(buildO, ".apk") {
+		return fmt.Errorf("output file name %q does not end in '.apk'", buildO)
+	}
+	var out io.Writer
+	if !buildN {
+		f, err := os.Create(buildO)
+		if err != nil {
+			return err
+		}
+		defer func() {
+			if cerr := f.Close(); err == nil {
+				err = cerr
+			}
+		}()
+		out = f
+	}
+
+	var apkw *Writer
+	if !buildN {
+		apkw = NewWriter(out, privKey)
+	}
+	apkwcreate := func(name string) (io.Writer, error) {
+		if buildV {
+			fmt.Fprintf(os.Stderr, "apk: %s\n", name)
+		}
+		if buildN {
+			return ioutil.Discard, nil
+		}
+		return apkw.Create(name)
+	}
+
+	w, err := apkwcreate("AndroidManifest.xml")
+	if err != nil {
+		return err
+	}
+	if _, err := w.Write(manifestData); err != nil {
+		return err
+	}
+
+	w, err = apkwcreate("lib/armeabi/lib" + libName + ".so")
+	if err != nil {
+		return err
+	}
+	if !buildN {
+		r, err := os.Open(libPath)
+		if err != nil {
+			return err
+		}
+		if _, err := io.Copy(w, r); err != nil {
+			return err
+		}
+	}
+
+	if pkgImportsAL(pkg) {
+		alDir := filepath.Join(ndkccpath, "openal/lib")
+		filepath.Walk(alDir, func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			if info.IsDir() {
+				return nil
+			}
+			name := "lib/" + path[len(alDir)+1:]
+			w, err := apkwcreate(name)
+			if err != nil {
+				return err
+			}
+			if !buildN {
+				f, err := os.Open(path)
+				if err != nil {
+					return err
+				}
+				defer f.Close()
+				_, err = io.Copy(w, f)
+			}
+			return err
+		})
+	}
+
+	// Add any assets.
+	assetsDir := filepath.Join(pkg.Dir, "assets")
+	assetsDirExists := true
+	fi, err := os.Stat(assetsDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			assetsDirExists = false
+		} else {
+			return err
+		}
+	} else {
+		assetsDirExists = fi.IsDir()
+	}
+	if assetsDirExists {
+		err = filepath.Walk(assetsDir, func(path string, info os.FileInfo, err error) error {
+			if err != nil {
+				return err
+			}
+			if info.IsDir() {
+				return nil
+			}
+			name := "assets/" + path[len(assetsDir)+1:]
+			w, err := apkwcreate(name)
+			if err != nil {
+				return err
+			}
+			f, err := os.Open(path)
+			if err != nil {
+				return err
+			}
+			defer f.Close()
+			_, err = io.Copy(w, f)
+			return err
+		})
+		if err != nil {
+			return fmt.Errorf("asset %v", err)
+		}
+	}
+
+	// TODO: add gdbserver to apk?
+
+	if !buildN {
+		if err := apkw.Close(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+var importsALPkg = make(map[string]struct{})
+
+// pkgImportsAL returns true if the given package or one of its
+// dependencies imports the x/mobile/exp/audio/al package.
+func pkgImportsAL(pkg *build.Package) bool {
+	for _, path := range pkg.Imports {
+		if path == "C" {
+			continue
+		}
+		if _, ok := importsALPkg[path]; ok {
+			continue
+		}
+		importsALPkg[path] = struct{}{}
+		if strings.HasPrefix(path, "golang.org/x/mobile/exp/audio/al") {
+			return true
+		}
+		dPkg, err := ctx.Import(path, "", build.ImportComment)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error reading OpenAL library: %v", err)
+			os.Exit(2)
+		}
+		if pkgImportsAL(dPkg) {
+			return true
+		}
+	}
+	return false
+}
+
+// A random uninteresting private key.
+// Must be consistent across builds so newer app versions can be installed.
+const debugCert = `
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----
+`

cmd/gomobile/build_iosapp.go

@@ -7,38 +7,26 @@ package main
 import (
 	"bytes"
 	"fmt"
+	"go/build"
 	"io"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path"
 	"path/filepath"
-	"strconv"
 	"strings"
 )
 
-func goIOSBuild(src string) error {
+func goIOSBuild(pkg *build.Package) error {
+	src := pkg.ImportPath
 	if buildO != "" && !strings.HasSuffix(buildO, ".app") {
 		return fmt.Errorf("-o must have an .app for target=ios")
 	}
 
-	dir := "$XCODEPROJ"
-	if !buildN {
-		tmp, err := ioutil.TempDir("", "xcodeproject")
-		if err != nil {
-			return err
-		}
-		dir = tmp
-		defer os.RemoveAll(dir)
-	}
-	if buildX {
-		printcmd("mkdir %s", dir)
-	}
-
 	layout := map[string][]byte{
-		dir + "/main.xcodeproj/project.pbxproj":                        []byte(projPbxproj),
+		tmpdir + "/main.xcodeproj/project.pbxproj":                        []byte(projPbxproj),
-		dir + "/main/Info.plist":                                       []byte(infoPlist),
+		tmpdir + "/main/Info.plist":                                       []byte(infoPlist),
-		dir + "/main/Images.xcassets/AppIcon.appiconset/Contents.json": []byte(contentsJSON),
+		tmpdir + "/main/Images.xcassets/AppIcon.appiconset/Contents.json": []byte(contentsJSON),
 	}
 
 	for dst, v := range layout {
@@ -55,20 +43,13 @@ func goIOSBuild(src string) error {
 		}
 	}
 
-	armPath := filepath.Join(dir, "arm")
+	armPath := filepath.Join(tmpdir, "arm")
-	if err := goBuild(src, armPath, []string{
+	if err := goBuild(src, darwinArmEnv, "-o="+armPath); err != nil {
-		`GOOS=darwin`,
-		`GOARCH=arm`,
-		`GOARM=7`,
-	}); err != nil {
 		return err
 	}
 
-	arm64Path := filepath.Join(dir, "arm64")
+	arm64Path := filepath.Join(tmpdir, "arm64")
-	if err := goBuild(src, arm64Path, []string{
+	if err := goBuild(src, darwinArm64Env, "-o="+arm64Path); err != nil {
-		`GOOS=darwin`,
-		`GOARCH=arm64`,
-	}); err != nil {
 		return err
 	}
 
@@ -77,13 +58,13 @@ func goIOSBuild(src string) error {
 	// TODO(jbd): Investigate the new announcements about iO9's fat binary
 	// size limitations are breaking this feature.
 	if buildX {
-		printcmd("xcrun lipo -create %s %s -o %s", armPath, arm64Path, filepath.Join(dir, "main/main"))
+		printcmd("xcrun lipo -create %s %s -o %s", armPath, arm64Path, filepath.Join(tmpdir, "main/main"))
 	}
 	if !buildN {
 		cmd := exec.Command(
 			"xcrun", "lipo",
 			"-create", armPath, arm64Path,
-			"-o", filepath.Join(dir, "main/main"),
+			"-o", filepath.Join(tmpdir, "main/main"),
 		)
 		cmd.Stderr = os.Stderr
 		if err := cmd.Run(); err != nil {
@@ -92,7 +73,7 @@ func goIOSBuild(src string) error {
 	}
 
 	// TODO(jbd): Set the launcher icon.
-	if err := iosCopyAssets(dir); err != nil {
+	if err := iosCopyAssets(pkg, tmpdir); err != nil {
 		return err
 	}
 
@@ -100,7 +81,7 @@ func goIOSBuild(src string) error {
 	cmd := exec.Command(
 		"xcrun", "xcodebuild",
 		"-configuration", "Release",
-		"-project", dir+"/main.xcodeproj",
+		"-project", tmpdir+"/main.xcodeproj",
 	)
 
 	if buildX {
@@ -128,21 +109,21 @@ func goIOSBuild(src string) error {
 		buildO = path.Base(pkg.ImportPath) + ".app"
 	}
 	if buildX {
-		printcmd("mv %s %s", dir+"/build/Release-iphoneos/main.app", buildO)
+		printcmd("mv %s %s", tmpdir+"/build/Release-iphoneos/main.app", buildO)
 	}
 	if !buildN {
 		// if output already exists, remove.
 		if err := os.RemoveAll(buildO); err != nil {
 			return err
 		}
-		if err := os.Rename(dir+"/build/Release-iphoneos/main.app", buildO); err != nil {
+		if err := os.Rename(tmpdir+"/build/Release-iphoneos/main.app", buildO); err != nil {
 			return err
 		}
 	}
 	return nil
 }
 
-func iosCopyAssets(xcodeProjDir string) error {
+func iosCopyAssets(pkg *build.Package, xcodeProjDir string) error {
 	dstAssets := xcodeProjDir + "/main/assets"
 	if buildX {
 		printcmd("mkdir -p %s", dstAssets)
@@ -199,45 +180,6 @@ func iosCopyAssets(xcodeProjDir string) error {
 	})
 }
 
-func goBuild(src, o string, env []string) error {
-	goroot := goEnv("GOROOT")
-	gopath := goEnv("GOPATH")
-	cmd := exec.Command(
-		`go`,
-		`build`,
-		`-tags=`+strconv.Quote(strings.Join(ctx.BuildTags, ",")),
-	)
-	if buildV {
-		cmd.Args = append(cmd.Args, "-v")
-	}
-	if buildI {
-		cmd.Args = append(cmd.Args, "-i")
-	}
-	if buildX {
-		cmd.Args = append(cmd.Args, "-x")
-	}
-	cmd.Args = append(cmd.Args, "-o="+o)
-	cmd.Args = append(cmd.Args, src)
-	// TODO(jbd): Remove clangwrap.sh dependency by implementing clangwrap.sh
-	// in Go in this package.
-	cmd.Env = append(env, []string{
-		`CGO_ENABLED=1`,
-		`GOROOT=` + goroot,
-		`GOPATH=` + gopath,
-		`CC=` + filepath.Join(goroot, "misc/ios/clangwrap.sh"),
-		`CCX=` + filepath.Join(goroot, "misc/ios/clangwrap.sh"),
-	}...)
-	cmd.Stderr = os.Stderr
-	if buildX {
-		printcmd("%s", strings.Join(cmd.Env, " ")+" "+strings.Join(cmd.Args, " "))
-	}
-	if !buildN {
-		cmd.Env = environ(cmd.Env)
-		return cmd.Run()
-	}
-	return nil
-}
-
 const infoPlist = `<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">

cmd/gomobile/build_test.go

@@ -46,8 +46,8 @@ func TestBuild(t *testing.T) {
 
 }
 
-var buildTmpl = template.Must(template.New("output").Parse(`WORK=$WORK
+var buildTmpl = template.Must(template.New("output").Parse(`GOMOBILE={{.GOPATH}}/pkg/gomobile
-GOMOBILE={{.GOPATH}}/pkg/gomobile
+WORK=$WORK
-GOOS=android GOARCH=arm GOARM=7 CGO_ENABLED=1 CC=$GOMOBILE/android-{{.NDK}}/arm/bin/arm-linux-androideabi-gcc{{.EXE}} CXX=$GOMOBILE/android-{{.NDK}}/arm/bin/arm-linux-androideabi-g++{{.EXE}} GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0" GOROOT=$GOROOT GOPATH=$GOPATH go build -tags="" -x -buildmode=c-shared -o $WORK/libbasic.so golang.org/x/mobile/example/basic
+GOOS=android GOARCH=arm GOARM=7 CC=$GOMOBILE/android-{{.NDK}}/arm/bin/arm-linux-androideabi-gcc{{.EXE}} CXX=$GOMOBILE/android-{{.NDK}}/arm/bin/arm-linux-androideabi-g++{{.EXE}} GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0" CGO_ENABLED=1 GOROOT=$GOROOT GOPATH=$GOPATH go build -tags="" -x -buildmode=c-shared -o $WORK/libbasic.so golang.org/x/mobile/example/basic
 rm -r -f "$WORK"
 `))

cmd/gomobile/doc.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// DO NOT EDIT. GENERATED BY 'gomobile help documentation'.
+// DO NOT EDIT. GENERATED BY 'gomobile help documentation doc.go'.
 
 /*
 Gomobile is a tool for building and running mobile apps written in Go.

cmd/gomobile/env.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// General mobile build environment. Initialized by envInit.
+var (
+	cwd          string
+	gomobilepath string // $GOPATH/pkg/gomobile
+	ndkccpath    string // $GOPATH/pkg/gomobile/android-{{.NDK}}
+
+	darwinArmEnv   []string
+	darwinArm64Env []string
+	androidArmEnv  []string
+)
+
+func envInit() (cleanup func(), err error) {
+	cwd, err = os.Getwd()
+	if err != nil {
+		return nil, err
+	}
+
+	// Find gomobilepath.
+	gopath := goEnv("GOPATH")
+	for _, p := range filepath.SplitList(gopath) {
+		gomobilepath = filepath.Join(p, "pkg", "gomobile")
+		if _, err := os.Stat(gomobilepath); err == nil {
+			break
+		}
+	}
+	if buildX {
+		fmt.Fprintln(xout, "GOMOBILE="+gomobilepath)
+	}
+
+	// Check the toolchain is in a good state.
+	version, err := goVersion()
+	if err != nil {
+		return nil, err
+	}
+	if gomobilepath == "" {
+		return nil, errors.New("toolchain not installed, run `gomobile init`")
+	}
+	verpath := filepath.Join(gomobilepath, "version")
+	installedVersion, err := ioutil.ReadFile(verpath)
+	if err != nil {
+		return nil, errors.New("toolchain partially installed, run `gomobile init`")
+	}
+	if !bytes.Equal(installedVersion, version) {
+		return nil, errors.New("toolchain out of date, run `gomobile init`")
+	}
+
+	// Setup the cross-compiler environments.
+
+	// TODO(crawshaw): Remove ndkccpath global.
+	ndkccpath = filepath.Join(gomobilepath, "android-"+ndkVersion)
+	ndkccbin := filepath.Join(ndkccpath, "arm", "bin")
+
+	androidEnv := []string{
+		"CC=" + filepath.Join(ndkccbin, "arm-linux-androideabi-gcc"),
+		"CXX=" + filepath.Join(ndkccbin, "arm-linux-androideabi-g++"),
+		`GOGCCFLAGS="-fPIC -marm -pthread -fmessage-length=0"`,
+	}
+	androidArmEnv = append([]string{
+		"GOOS=android",
+		"GOARCH=arm",
+		"GOARM=7",
+	}, androidEnv...)
+
+	// TODO(jbd): Remove clangwrap.sh dependency by implementing clangwrap.sh
+	// in Go in this package.
+	goroot := goEnv("GOROOT")
+	iosEnv := []string{
+		"CC=" + filepath.Join(goroot, "misc/ios/clangwrap.sh"),
+		"CCX=" + filepath.Join(goroot, "misc/ios/clangwrap.sh"),
+	}
+	darwinArmEnv = append([]string{
+		"GOOS=darwin",
+		"GOARCH=arm",
+	}, iosEnv...)
+	darwinArm64Env = append([]string{
+		"GOOS=darwin",
+		"GOARCH=arm64",
+	}, iosEnv...)
+
+	// We need a temporary directory when assembling an apk/app.
+	if buildN {
+		tmpdir = "$WORK"
+	} else {
+		tmpdir, err = ioutil.TempDir("", "gomobile-work-")
+		if err != nil {
+			return nil, err
+		}
+	}
+	if buildX {
+		fmt.Fprintln(xout, "WORK="+tmpdir)
+	}
+
+	return func() { removeAll(tmpdir) }, nil
+}

cmd/gomobile/init.go

@@ -4,7 +4,6 @@
 
 package main
 
-// TODO(crawshaw): build darwin/arm cross compiler on darwin/{386,amd64}
 // TODO(crawshaw): android/{386,arm64}
 
 import (