go/build, cmd/go: don't expect gccgo to have GOROOT packages

When using gccgo the standard library sources are not available in
GOROOT. Don't expect them to be there. In the gccgo build, use a set
of standard library packages generated at build time.

Change-Id: Id133022604d9b7e778e73e8512f9080c61462fba
Reviewed-on: https://go-review.googlesource.com/111595
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/go/internal/test/test.go

@@ -626,6 +626,11 @@ func runTest(cmd *base.Command, args []string) {
 
 		a := &work.Action{Mode: "go test -i"}
 		for _, p := range load.PackagesForBuild(all) {
+			if cfg.BuildToolchainName == "gccgo" && p.Standard {
+				// gccgo's standard library packages
+				// can not be reinstalled.
+				continue
+			}
 			a.Deps = append(a.Deps, b.CompileAction(work.ModeInstall, work.ModeInstall, p))
 		}
 		b.Do(a)

src/go/build/build.go

@@ -238,7 +238,7 @@ func (ctxt *Context) gopath() []string {
 // that do not exist.
 func (ctxt *Context) SrcDirs() []string {
 	var all []string
-	if ctxt.GOROOT != "" {
+	if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
 		dir := ctxt.joinPath(ctxt.GOROOT, "src")
 		if ctxt.isDir(dir) {
 			all = append(all, dir)
@@ -538,7 +538,7 @@ func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Packa
 		inTestdata := func(sub string) bool {
 			return strings.Contains(sub, "/testdata/") || strings.HasSuffix(sub, "/testdata") || strings.HasPrefix(sub, "testdata/") || sub == "testdata"
 		}
-		if ctxt.GOROOT != "" {
+		if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
 			root := ctxt.joinPath(ctxt.GOROOT, "src")
 			if sub, ok := ctxt.hasSubdir(root, p.Dir); ok && !inTestdata(sub) {
 				p.Goroot = true
@@ -555,7 +555,7 @@ func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Packa
 				// We found a potential import path for dir,
 				// but check that using it wouldn't find something
 				// else first.
-				if ctxt.GOROOT != "" {
+				if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
 					if dir := ctxt.joinPath(ctxt.GOROOT, "src", sub); ctxt.isDir(dir) {
 						p.ConflictDir = dir
 						goto Found
@@ -620,7 +620,7 @@ func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Packa
 				}
 				return false
 			}
-			if searchVendor(ctxt.GOROOT, true) {
+			if ctxt.Compiler != "gccgo" && searchVendor(ctxt.GOROOT, true) {
 				goto Found
 			}
 			for _, root := range gopath {
@@ -633,16 +633,24 @@ func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Packa
 		// Determine directory from import path.
 		if ctxt.GOROOT != "" {
 			dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
-			isDir := ctxt.isDir(dir)
-			binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
-			if isDir || binaryOnly {
-				p.Dir = dir
-				p.Goroot = true
-				p.Root = ctxt.GOROOT
-				goto Found
+			if ctxt.Compiler != "gccgo" {
+				isDir := ctxt.isDir(dir)
+				binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
+				if isDir || binaryOnly {
+					p.Dir = dir
+					p.Goroot = true
+					p.Root = ctxt.GOROOT
+					goto Found
+				}
 			}
 			tried.goroot = dir
 		}
+		if ctxt.Compiler == "gccgo" && isStandardPackage(path) {
+			p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
+			p.Goroot = true
+			p.Root = ctxt.GOROOT
+			goto Found
+		}
 		for _, root := range gopath {
 			dir := ctxt.joinPath(root, "src", path)
 			isDir := ctxt.isDir(dir)
@@ -706,6 +714,11 @@ Found:
 		return p, pkgerr
 	}
 
+	if ctxt.Compiler == "gccgo" && p.Goroot {
+		// gccgo has no sources for GOROOT packages.
+		return p, nil
+	}
+
 	dirs, err := ctxt.readDir(p.Dir)
 	if err != nil {
 		return p, err

src/go/build/gc.go

@@ -7,11 +7,131 @@
 package build
 
 import (
+	"os"
+	"os/exec"
 	"path/filepath"
 	"runtime"
+	"strings"
+	"sync"
 )
 
 // getToolDir returns the default value of ToolDir.
 func getToolDir() string {
 	return filepath.Join(runtime.GOROOT(), "pkg/tool/"+runtime.GOOS+"_"+runtime.GOARCH)
 }
+
+// isStandardPackage is not used for the gc toolchain.
+// However, this function may be called when using `go build -compiler=gccgo`.
+func isStandardPackage(path string) bool {
+	return gccgoSearch.isStandard(path)
+}
+
+// gccgoSearch holds the gccgo search directories.
+type gccgoDirs struct {
+	once sync.Once
+	dirs []string
+}
+
+// gccgoSearch is used to check whether a gccgo package exists in the
+// standard library.
+var gccgoSearch gccgoDirs
+
+// init finds the gccgo search directories. If this fails it leaves dirs == nil.
+func (gd *gccgoDirs) init() {
+	gccgo := os.Getenv("GCCGO")
+	if gccgo == "" {
+		gccgo = "gccgo"
+	}
+	bin, err := exec.LookPath(gccgo)
+	if err != nil {
+		return
+	}
+
+	allDirs, err := exec.Command(bin, "-print-search-dirs").Output()
+	if err != nil {
+		return
+	}
+	versionB, err := exec.Command(bin, "-dumpversion").Output()
+	if err != nil {
+		return
+	}
+	version := strings.TrimSpace(string(versionB))
+	machineB, err := exec.Command(bin, "-dumpmachine").Output()
+	if err != nil {
+		return
+	}
+	machine := strings.TrimSpace(string(machineB))
+
+	dirsEntries := strings.Split(string(allDirs), "\n")
+	const prefix = "libraries: ="
+	var dirs []string
+	for _, dirEntry := range dirsEntries {
+		if strings.HasPrefix(dirEntry, prefix) {
+			dirs = filepath.SplitList(strings.TrimPrefix(dirEntry, prefix))
+			break
+		}
+	}
+	if len(dirs) == 0 {
+		return
+	}
+
+	var lastDirs []string
+	for _, dir := range dirs {
+		goDir := filepath.Join(dir, "go", version)
+		if fi, err := os.Stat(goDir); err == nil && fi.IsDir() {
+			gd.dirs = append(gd.dirs, goDir)
+			goDir = filepath.Join(goDir, machine)
+			if fi, err = os.Stat(goDir); err == nil && fi.IsDir() {
+				gd.dirs = append(gd.dirs, goDir)
+			}
+		}
+		if fi, err := os.Stat(dir); err == nil && fi.IsDir() {
+			lastDirs = append(lastDirs, dir)
+		}
+	}
+	gd.dirs = append(gd.dirs, lastDirs...)
+}
+
+// isStandard returns whether path is a standard library for gccgo.
+func (gd *gccgoDirs) isStandard(path string) bool {
+	// Quick check: if the first path component has a '.', it's not
+	// in the standard library. This skips most GOPATH directories.
+	i := strings.Index(path, "/")
+	if i < 0 {
+		i = len(path)
+	}
+	if strings.Contains(path[:i], ".") {
+		return false
+	}
+
+	if path == "unsafe" {
+		// Special case.
+		return true
+	}
+
+	gd.once.Do(gd.init)
+	if gd.dirs == nil {
+		// We couldn't find the gccgo search directories.
+		// Best guess, since the first component did not contain
+		// '.', is that this is a standard library package.
+		return true
+	}
+
+	for _, dir := range gd.dirs {
+		full := filepath.Join(dir, path)
+		pkgdir, pkg := filepath.Split(full)
+		for _, p := range [...]string{
+			full,
+			full + ".gox",
+			pkgdir + "lib" + pkg + ".so",
+			pkgdir + "lib" + pkg + ".a",
+			full + ".o",
+		} {
+			if fi, err := os.Stat(p); err == nil && !fi.IsDir() {
+				return true
+			}
+		}
+	}
+
+	return false
+}

src/go/build/gccgo.go

@@ -12,3 +12,9 @@ import "runtime"
 func getToolDir() string {
 	return envOr("GCCGOTOOLDIR", runtime.GCCGOTOOLDIR)
 }
+
+// isStandardPackage returns whether path names a standard library package.
+// This uses a list generated at build time.
+func isStandardPackage(path string) bool {
+	return stdpkg[path]
+}