2 files changed, 158 insertions, 0 deletions
diff --git a/src/internal/goroot/gc.go b/src/internal/goroot/gc.go
new file mode 100644
index 0000000..ce72bc3
--- /dev/null
+++ b/src/internal/goroot/gc.go
@@ -0,0 +1,131 @@
+// Copyright 2018 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.
+
+// +build gc
+
+package goroot
+
+import (
+	exec "internal/execabs"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// IsStandardPackage reports whether path is a standard package,
+// given goroot and compiler.
+func IsStandardPackage(goroot, compiler, path string) bool {
+	switch compiler {
+	case "gc":
+		dir := filepath.Join(goroot, "src", path)
+		_, err := os.Stat(dir)
+		return err == nil
+	case "gccgo":
+		return gccgoSearch.isStandard(path)
+	default:
+		panic("unknown compiler " + compiler)
+	}
+}
+
+// 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 reports 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) + ".gox"
+		if fi, err := os.Stat(full); err == nil && !fi.IsDir() {
+			return true
+		}
+	}
+
+	return false
+}
diff --git a/src/internal/goroot/gccgo.go b/src/internal/goroot/gccgo.go
new file mode 100644
index 0000000..3530e59
--- /dev/null
+++ b/src/internal/goroot/gccgo.go
@@ -0,0 +1,27 @@
+// Copyright 2018 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.
+
+// +build gccgo
+
+package goroot
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// IsStandardPackage reports whether path is a standard package,
+// given goroot and compiler.
+func IsStandardPackage(goroot, compiler, path string) bool {
+	switch compiler {
+	case "gc":
+		dir := filepath.Join(goroot, "src", path)
+		_, err := os.Stat(dir)
+		return err == nil
+	case "gccgo":
+		return stdpkg[path]
+	default:
+		panic("unknown compiler " + compiler)
+	}
+}