Imported Upstream version 60upstream/60

14 files changed, 1026 insertions, 0 deletions

diff --git a/src/pkg/go/build/Makefile b/src/pkg/go/build/Makefile
new file mode 100644
index 000000000..349e00e80
--- /dev/null
+++ b/src/pkg/go/build/Makefile
@@ -0,0 +1,22 @@
+# Copyright 2009 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.
+
+include ../../../Make.inc
+
+TARG=go/build
+GOFILES=\
+	build.go\
+	dir.go\
+	path.go\
+	syslist.go\
+
+CLEANFILES+=syslist.go pkgtest/_obj cmdtest/_obj cgotest/_obj
+
+include ../../../Make.pkg
+
+syslist.go: ../../../Make.inc Makefile
+	echo '// Generated automatically by make.' >$@
+	echo 'package build' >>$@
+	echo 'const goosList = "$(GOOS_LIST)"' >>$@
+	echo 'const goarchList = "$(GOARCH_LIST)"' >>$@
diff --git a/src/pkg/go/build/build.go b/src/pkg/go/build/build.go
new file mode 100644
index 000000000..97f92bfb6
--- /dev/null
+++ b/src/pkg/go/build/build.go
@@ -0,0 +1,444 @@
+// Copyright 2011 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 build provides tools for building Go packages.
+package build
+
+import (
+	"bytes"
+	"exec"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+)
+
+// Build produces a build Script for the given package.
+func Build(tree *Tree, pkg string, info *DirInfo) (*Script, os.Error) {
+	s := &Script{}
+	b := &build{
+		script: s,
+		path:   filepath.Join(tree.SrcDir(), pkg),
+	}
+	b.obj = b.abs("_obj") + string(filepath.Separator)
+
+	b.goarch = runtime.GOARCH
+	if g := os.Getenv("GOARCH"); g != "" {
+		b.goarch = g
+	}
+	var err os.Error
+	b.arch, err = ArchChar(b.goarch)
+	if err != nil {
+		return nil, err
+	}
+
+	// add import object files to list of Inputs
+	for _, pkg := range info.Imports {
+		t, p, err := FindTree(pkg)
+		if err != nil && err != ErrNotFound {
+			// FindTree should always be able to suggest an import
+			// path and tree. The path must be malformed
+			// (for example, an absolute or relative path).
+			return nil, os.NewError("build: invalid import: " + pkg)
+		}
+		s.addInput(filepath.Join(t.PkgDir(), p+".a"))
+	}
+
+	// .go files to be built with gc
+	gofiles := b.abss(info.GoFiles...)
+	s.addInput(gofiles...)
+
+	var ofiles []string // object files to be linked or packed
+
+	// make build directory
+	b.mkdir(b.obj)
+	s.addIntermediate(b.obj)
+
+	// cgo
+	if len(info.CgoFiles) > 0 {
+		cgoFiles := b.abss(info.CgoFiles...)
+		s.addInput(cgoFiles...)
+		cgoCFiles := b.abss(info.CFiles...)
+		s.addInput(cgoCFiles...)
+		outGo, outObj := b.cgo(cgoFiles, cgoCFiles)
+		gofiles = append(gofiles, outGo...)
+		ofiles = append(ofiles, outObj...)
+		s.addIntermediate(outGo...)
+		s.addIntermediate(outObj...)
+	}
+
+	// compile
+	if len(gofiles) > 0 {
+		ofile := b.obj + "_go_." + b.arch
+		b.gc(ofile, gofiles...)
+		ofiles = append(ofiles, ofile)
+		s.addIntermediate(ofile)
+	}
+
+	// assemble
+	for _, sfile := range info.SFiles {
+		ofile := b.obj + sfile[:len(sfile)-1] + b.arch
+		sfile = b.abs(sfile)
+		s.addInput(sfile)
+		b.asm(ofile, sfile)
+		ofiles = append(ofiles, ofile)
+		s.addIntermediate(ofile)
+	}
+
+	if len(ofiles) == 0 {
+		return nil, os.NewError("make: no object files to build")
+	}
+
+	// choose target file
+	var targ string
+	if info.IsCommand() {
+		// use the last part of the import path as binary name
+		_, bin := filepath.Split(pkg)
+		if runtime.GOOS == "windows" {
+			bin += ".exe"
+		}
+		targ = filepath.Join(tree.BinDir(), bin)
+	} else {
+		targ = filepath.Join(tree.PkgDir(), pkg+".a")
+	}
+
+	// make target directory
+	targDir, _ := filepath.Split(targ)
+	b.mkdir(targDir)
+
+	// link binary or pack object
+	if info.IsCommand() {
+		b.ld(targ, ofiles...)
+	} else {
+		b.gopack(targ, ofiles...)
+	}
+	s.Output = append(s.Output, targ)
+
+	return b.script, nil
+}
+
+// A Script describes the build process for a Go package.
+// The Input, Intermediate, and Output fields are lists of absolute paths.
+type Script struct {
+	Cmd          []*Cmd
+	Input        []string
+	Intermediate []string
+	Output       []string
+}
+
+func (s *Script) addInput(file ...string) {
+	s.Input = append(s.Input, file...)
+}
+
+func (s *Script) addIntermediate(file ...string) {
+	s.Intermediate = append(s.Intermediate, file...)
+}
+
+// Run runs the Script's Cmds in order.
+func (s *Script) Run() os.Error {
+	for _, c := range s.Cmd {
+		if err := c.Run(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Stale returns true if the build's inputs are newer than its outputs.
+func (s *Script) Stale() bool {
+	var latest int64
+	// get latest mtime of outputs
+	for _, file := range s.Output {
+		fi, err := os.Stat(file)
+		if err != nil {
+			// any error reading output files means stale
+			return true
+		}
+		if m := fi.Mtime_ns; m > latest {
+			latest = m
+		}
+	}
+	for _, file := range s.Input {
+		fi, err := os.Stat(file)
+		if err != nil || fi.Mtime_ns > latest {
+			// any error reading input files means stale
+			// (attempt to rebuild to figure out why)
+			return true
+		}
+	}
+	return false
+}
+
+// Clean removes the Script's Intermediate files.
+// It tries to remove every file and returns the first error it encounters.
+func (s *Script) Clean() (err os.Error) {
+	// Reverse order so that directories get removed after the files they contain.
+	for i := len(s.Intermediate) - 1; i >= 0; i-- {
+		if e := os.Remove(s.Intermediate[i]); err == nil {
+			err = e
+		}
+	}
+	return
+}
+
+// Nuke removes the Script's Intermediate and Output files.
+// It tries to remove every file and returns the first error it encounters.
+func (s *Script) Nuke() (err os.Error) {
+	// Reverse order so that directories get removed after the files they contain.
+	for i := len(s.Output) - 1; i >= 0; i-- {
+		if e := os.Remove(s.Output[i]); err == nil {
+			err = e
+		}
+	}
+	if e := s.Clean(); err == nil {
+		err = e
+	}
+	return
+}
+
+// A Cmd describes an individual build command.
+type Cmd struct {
+	Args   []string // command-line
+	Stdout string   // write standard output to this file, "" is passthrough
+	Dir    string   // working directory
+	Env    []string // environment
+	Input  []string // file paths (dependencies)
+	Output []string // file paths
+}
+
+func (c *Cmd) String() string {
+	return strings.Join(c.Args, " ")
+}
+
+// Run executes the Cmd.
+func (c *Cmd) Run() os.Error {
+	if c.Args[0] == "mkdir" {
+		for _, p := range c.Output {
+			if err := os.MkdirAll(p, 0777); err != nil {
+				return fmt.Errorf("command %q: %v", c, err)
+			}
+		}
+		return nil
+	}
+	out := new(bytes.Buffer)
+	cmd := exec.Command(c.Args[0], c.Args[1:]...)
+	cmd.Dir = c.Dir
+	cmd.Env = c.Env
+	cmd.Stdout = out
+	cmd.Stderr = out
+	if c.Stdout != "" {
+		f, err := os.Create(c.Stdout)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		cmd.Stdout = f
+	}
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("command %q: %v\n%v", c, err, out)
+	}
+	return nil
+}
+
+// ArchChar returns the architecture character for the given goarch.
+// For example, ArchChar("amd64") returns "6".
+func ArchChar(goarch string) (string, os.Error) {
+	switch goarch {
+	case "386":
+		return "8", nil
+	case "amd64":
+		return "6", nil
+	case "arm":
+		return "5", nil
+	}
+	return "", os.NewError("unsupported GOARCH " + goarch)
+}
+
+type build struct {
+	script *Script
+	path   string
+	obj    string
+	goarch string
+	arch   string
+}
+
+func (b *build) abs(file string) string {
+	if filepath.IsAbs(file) {
+		return file
+	}
+	return filepath.Join(b.path, file)
+}
+
+func (b *build) abss(file ...string) []string {
+	s := make([]string, len(file))
+	for i, f := range file {
+		s[i] = b.abs(f)
+	}
+	return s
+}
+
+func (b *build) add(c Cmd) {
+	b.script.Cmd = append(b.script.Cmd, &c)
+}
+
+func (b *build) mkdir(name string) {
+	b.add(Cmd{
+		Args:   []string{"mkdir", "-p", name},
+		Output: []string{name},
+	})
+}
+
+func (b *build) gc(ofile string, gofiles ...string) {
+	gc := b.arch + "g"
+	args := append([]string{gc, "-o", ofile}, gcImportArgs...)
+	args = append(args, gofiles...)
+	b.add(Cmd{
+		Args:   args,
+		Input:  gofiles,
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) asm(ofile string, sfile string) {
+	asm := b.arch + "a"
+	b.add(Cmd{
+		Args:   []string{asm, "-o", ofile, sfile},
+		Input:  []string{sfile},
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) ld(targ string, ofiles ...string) {
+	ld := b.arch + "l"
+	args := append([]string{ld, "-o", targ}, ldImportArgs...)
+	args = append(args, ofiles...)
+	b.add(Cmd{
+		Args:   args,
+		Input:  ofiles,
+		Output: []string{targ},
+	})
+}
+
+func (b *build) gopack(targ string, ofiles ...string) {
+	b.add(Cmd{
+		Args:   append([]string{"gopack", "grc", targ}, ofiles...),
+		Input:  ofiles,
+		Output: []string{targ},
+	})
+}
+
+func (b *build) cc(ofile string, cfiles ...string) {
+	cc := b.arch + "c"
+	dir := fmt.Sprintf("%s_%s", runtime.GOOS, runtime.GOARCH)
+	inc := filepath.Join(runtime.GOROOT(), "pkg", dir)
+	args := []string{cc, "-FVw", "-I", inc, "-o", ofile}
+	b.add(Cmd{
+		Args:   append(args, cfiles...),
+		Input:  cfiles,
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) gccCompile(ofile, cfile string) {
+	b.add(Cmd{
+		Args:   b.gccArgs("-o", ofile, "-c", cfile),
+		Input:  []string{cfile},
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) gccLink(ofile string, ofiles ...string) {
+	b.add(Cmd{
+		Args:   append(b.gccArgs("-o", ofile), ofiles...),
+		Input:  ofiles,
+		Output: []string{ofile},
+	})
+}
+
+func (b *build) gccArgs(args ...string) []string {
+	// TODO(adg): HOST_CC
+	a := []string{"gcc", "-I", b.path, "-g", "-fPIC", "-O2"}
+	switch b.arch {
+	case "8":
+		a = append(a, "-m32")
+	case "6":
+		a = append(a, "-m64")
+	}
+	return append(a, args...)
+}
+
+var cgoRe = regexp.MustCompile(`[/\\:]`)
+
+func (b *build) cgo(cgofiles, cgocfiles []string) (outGo, outObj []string) {
+	// cgo
+	// TODO(adg): CGOPKGPATH
+	// TODO(adg): CGO_FLAGS
+	gofiles := []string{b.obj + "_cgo_gotypes.go"}
+	cfiles := []string{b.obj + "_cgo_main.c", b.obj + "_cgo_export.c"}
+	for _, fn := range cgofiles {
+		f := b.obj + cgoRe.ReplaceAllString(fn[:len(fn)-2], "_")
+		gofiles = append(gofiles, f+"cgo1.go")
+		cfiles = append(cfiles, f+"cgo2.c")
+	}
+	defunC := b.obj + "_cgo_defun.c"
+	output := append([]string{defunC}, cfiles...)
+	output = append(output, gofiles...)
+	b.add(Cmd{
+		Args:   append([]string{"cgo", "--"}, cgofiles...),
+		Dir:    b.path,
+		Env:    append(os.Environ(), "GOARCH="+b.goarch),
+		Input:  cgofiles,
+		Output: output,
+	})
+	outGo = append(outGo, gofiles...)
+	exportH := filepath.Join(b.path, "_cgo_export.h")
+	b.script.addIntermediate(defunC, exportH, b.obj+"_cgo_flags")
+	b.script.addIntermediate(cfiles...)
+
+	// cc _cgo_defun.c
+	defunObj := b.obj + "_cgo_defun." + b.arch
+	b.cc(defunObj, defunC)
+	outObj = append(outObj, defunObj)
+
+	// gcc
+	linkobj := make([]string, 0, len(cfiles))
+	for _, cfile := range cfiles {
+		ofile := cfile[:len(cfile)-1] + "o"
+		b.gccCompile(ofile, cfile)
+		linkobj = append(linkobj, ofile)
+		if !strings.HasSuffix(ofile, "_cgo_main.o") {
+			outObj = append(outObj, ofile)
+		} else {
+			b.script.addIntermediate(ofile)
+		}
+	}
+	for _, cfile := range cgocfiles {
+		ofile := b.obj + cgoRe.ReplaceAllString(cfile[:len(cfile)-1], "_") + "o"
+		b.gccCompile(ofile, cfile)
+		linkobj = append(linkobj, ofile)
+		outObj = append(outObj, ofile)
+	}
+	dynObj := b.obj + "_cgo_.o"
+	b.gccLink(dynObj, linkobj...)
+	b.script.addIntermediate(dynObj)
+
+	// cgo -dynimport
+	importC := b.obj + "_cgo_import.c"
+	b.add(Cmd{
+		Args:   []string{"cgo", "-dynimport", dynObj},
+		Stdout: importC,
+		Input:  []string{dynObj},
+		Output: []string{importC},
+	})
+	b.script.addIntermediate(importC)
+
+	// cc _cgo_import.ARCH
+	importObj := b.obj + "_cgo_import." + b.arch
+	b.cc(importObj, importC)
+	outObj = append(outObj, importObj)
+
+	return
+}
diff --git a/src/pkg/go/build/build_test.go b/src/pkg/go/build/build_test.go
new file mode 100644
index 000000000..e59d87672
--- /dev/null
+++ b/src/pkg/go/build/build_test.go
@@ -0,0 +1,61 @@
+// Copyright 2011 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 build
+
+import (
+	"exec"
+	"path/filepath"
+	"testing"
+)
+
+var buildPkgs = []string{
+	"go/build/pkgtest",
+	"go/build/cmdtest",
+	"go/build/cgotest",
+}
+
+const cmdtestOutput = "3"
+
+func TestBuild(t *testing.T) {
+	for _, pkg := range buildPkgs {
+		tree := Path[0] // Goroot
+		dir := filepath.Join(tree.SrcDir(), pkg)
+
+		info, err := ScanDir(dir, true)
+		if err != nil {
+			t.Error("ScanDir:", err)
+			continue
+		}
+
+		s, err := Build(tree, pkg, info)
+		if err != nil {
+			t.Error("Build:", err)
+			continue
+		}
+
+		if err := s.Run(); err != nil {
+			t.Error("Run:", err)
+			continue
+		}
+
+		if pkg == "go/build/cmdtest" {
+			bin := s.Output[0]
+			b, err := exec.Command(bin).CombinedOutput()
+			if err != nil {
+				t.Errorf("exec: %s: %v", bin, err)
+				continue
+			}
+			if string(b) != cmdtestOutput {
+				t.Errorf("cmdtest output: %s want: %s", b, cmdtestOutput)
+			}
+		}
+
+		defer func(s *Script) {
+			if err := s.Nuke(); err != nil {
+				t.Errorf("nuking: %v", err)
+			}
+		}(s)
+	}
+}
diff --git a/src/pkg/go/build/cgotest/cgotest.c b/src/pkg/go/build/cgotest/cgotest.c
new file mode 100644
index 000000000..b13acb227
--- /dev/null
+++ b/src/pkg/go/build/cgotest/cgotest.c
@@ -0,0 +1,9 @@
+// Copyright 2011 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.
+
+int
+Add(int x, int y, int *sum)
+{
+	sum = x+y;
+}
diff --git a/src/pkg/go/build/cgotest/cgotest.go b/src/pkg/go/build/cgotest/cgotest.go
new file mode 100644
index 000000000..93bbf0688
--- /dev/null
+++ b/src/pkg/go/build/cgotest/cgotest.go
@@ -0,0 +1,19 @@
+// Copyright 2011 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 cgotest
+
+/*
+char* greeting = "hello, world";
+*/
+// #include "cgotest.h"
+import "C"
+import "unsafe"
+
+var Greeting = C.GoString(C.greeting)
+
+func DoAdd(x, y int) (sum int) {
+	C.Add(C.int(x), C.int(y), (*C.int)(unsafe.Pointer(&sum)))
+	return
+}
diff --git a/src/pkg/go/build/cgotest/cgotest.h b/src/pkg/go/build/cgotest/cgotest.h
new file mode 100644
index 000000000..9c73643b6
--- /dev/null
+++ b/src/pkg/go/build/cgotest/cgotest.h
@@ -0,0 +1,5 @@
+// Copyright 2011 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.
+
+extern int Add(int, int, int *);
diff --git a/src/pkg/go/build/cmdtest/main.go b/src/pkg/go/build/cmdtest/main.go
new file mode 100644
index 000000000..bed4f485a
--- /dev/null
+++ b/src/pkg/go/build/cmdtest/main.go
@@ -0,0 +1,12 @@
+// Copyright 2011 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 "go/build/pkgtest"
+
+func main() {
+	pkgtest.Foo()
+	print(int(pkgtest.Sqrt(9)))
+}
diff --git a/src/pkg/go/build/dir.go b/src/pkg/go/build/dir.go
new file mode 100644
index 000000000..e0000b534
--- /dev/null
+++ b/src/pkg/go/build/dir.go
@@ -0,0 +1,172 @@
+// Copyright 2011 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 build
+
+import (
+	"go/parser"
+	"go/token"
+	"log"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"runtime"
+)
+
+type DirInfo struct {
+	GoFiles  []string // .go files in dir (excluding CgoFiles)
+	CgoFiles []string // .go files that import "C"
+	CFiles   []string // .c files in dir
+	SFiles   []string // .s files in dir
+	Imports  []string // All packages imported by goFiles
+	PkgName  string   // Name of package in dir
+}
+
+func (d *DirInfo) IsCommand() bool {
+	return d.PkgName == "main"
+}
+
+// ScanDir returns a structure with details about the Go content found
+// in the given directory. The file lists exclude:
+//
+//	- files in package main (unless allowMain is true)
+//	- files in package documentation
+//	- files ending in _test.go
+// 	- files starting with _ or .
+//
+// Only files that satisfy the goodOSArch function are included.
+func ScanDir(dir string, allowMain bool) (info *DirInfo, err os.Error) {
+	f, err := os.Open(dir)
+	if err != nil {
+		return nil, err
+	}
+	dirs, err := f.Readdir(-1)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	var di DirInfo
+	imported := make(map[string]bool)
+	fset := token.NewFileSet()
+	for i := range dirs {
+		d := &dirs[i]
+		if strings.HasPrefix(d.Name, "_") ||
+			strings.HasPrefix(d.Name, ".") {
+			continue
+		}
+		if !goodOSArch(d.Name) {
+			continue
+		}
+
+		switch filepath.Ext(d.Name) {
+		case ".go":
+			if strings.HasSuffix(d.Name, "_test.go") {
+				continue
+			}
+		case ".c":
+			di.CFiles = append(di.CFiles, d.Name)
+			continue
+		case ".s":
+			di.SFiles = append(di.SFiles, d.Name)
+			continue
+		default:
+			continue
+		}
+
+		filename := filepath.Join(dir, d.Name)
+		pf, err := parser.ParseFile(fset, filename, nil, parser.ImportsOnly)
+		if err != nil {
+			return nil, err
+		}
+		s := string(pf.Name.Name)
+		if s == "main" && !allowMain {
+			continue
+		}
+		if s == "documentation" {
+			continue
+		}
+		if di.PkgName == "" {
+			di.PkgName = s
+		} else if di.PkgName != s {
+			// Only if all files in the directory are in package main
+			// do we return PkgName=="main".
+			// A mix of main and another package reverts
+			// to the original (allowMain=false) behaviour.
+			if s == "main" || di.PkgName == "main" {
+				return ScanDir(dir, false)
+			}
+			return nil, os.NewError("multiple package names in " + dir)
+		}
+		isCgo := false
+		for _, spec := range pf.Imports {
+			quoted := string(spec.Path.Value)
+			path, err := strconv.Unquote(quoted)
+			if err != nil {
+				log.Panicf("%s: parser returned invalid quoted string: <%s>", filename, quoted)
+			}
+			imported[path] = true
+			if path == "C" {
+				isCgo = true
+			}
+		}
+		if isCgo {
+			di.CgoFiles = append(di.CgoFiles, d.Name)
+		} else {
+			di.GoFiles = append(di.GoFiles, d.Name)
+		}
+	}
+	di.Imports = make([]string, len(imported))
+	i := 0
+	for p := range imported {
+		di.Imports[i] = p
+		i++
+	}
+	return &di, nil
+}
+
+// goodOSArch returns false if the filename contains a $GOOS or $GOARCH
+// suffix which does not match the current system.
+// The recognized filename formats are:
+//
+//     name_$(GOOS).*
+//     name_$(GOARCH).*
+//     name_$(GOOS)_$(GOARCH).*
+//
+func goodOSArch(filename string) bool {
+	if dot := strings.Index(filename, "."); dot != -1 {
+		filename = filename[:dot]
+	}
+	l := strings.Split(filename, "_")
+	n := len(l)
+	if n == 0 {
+		return true
+	}
+	if good, known := goodOS[l[n-1]]; known {
+		return good
+	}
+	if good, known := goodArch[l[n-1]]; known {
+		if !good || n < 2 {
+			return false
+		}
+		good, known = goodOS[l[n-2]]
+		return good || !known
+	}
+	return true
+}
+
+var goodOS = make(map[string]bool)
+var goodArch = make(map[string]bool)
+
+func init() {
+	goodOS = make(map[string]bool)
+	goodArch = make(map[string]bool)
+	for _, v := range strings.Fields(goosList) {
+		goodOS[v] = v == runtime.GOOS
+	}
+	for _, v := range strings.Fields(goarchList) {
+		goodArch[v] = v == runtime.GOARCH
+	}
+}
diff --git a/src/pkg/go/build/path.go b/src/pkg/go/build/path.go
new file mode 100644
index 000000000..e39b5f8fa
--- /dev/null
+++ b/src/pkg/go/build/path.go
@@ -0,0 +1,182 @@
+// Copyright 2011 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 build
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+// Path is a validated list of Trees derived from $GOROOT and $GOPATH at init.
+var Path []*Tree
+
+// Tree describes a Go source tree, either $GOROOT or one from $GOPATH.
+type Tree struct {
+	Path   string
+	Goroot bool
+}
+
+func newTree(p string) (*Tree, os.Error) {
+	if !filepath.IsAbs(p) {
+		return nil, os.NewError("must be absolute")
+	}
+	ep, err := filepath.EvalSymlinks(p)
+	if err != nil {
+		return nil, err
+	}
+	return &Tree{Path: ep}, nil
+}
+
+// SrcDir returns the tree's package source directory.
+func (t *Tree) SrcDir() string {
+	if t.Goroot {
+		return filepath.Join(t.Path, "src", "pkg")
+	}
+	return filepath.Join(t.Path, "src")
+}
+
+// PkgDir returns the tree's package object directory.
+func (t *Tree) PkgDir() string {
+	goos, goarch := runtime.GOOS, runtime.GOARCH
+	if e := os.Getenv("GOOS"); e != "" {
+		goos = e
+	}
+	if e := os.Getenv("GOARCH"); e != "" {
+		goarch = e
+	}
+	return filepath.Join(t.Path, "pkg", goos+"_"+goarch)
+}
+
+// BinDir returns the tree's binary executable directory.
+func (t *Tree) BinDir() string {
+	if t.Goroot {
+		if gobin := os.Getenv("GOBIN"); gobin != "" {
+			return gobin
+		}
+	}
+	return filepath.Join(t.Path, "bin")
+}
+
+// HasSrc returns whether the given package's
+// source can be found inside this Tree.
+func (t *Tree) HasSrc(pkg string) bool {
+	fi, err := os.Stat(filepath.Join(t.SrcDir(), pkg))
+	if err != nil {
+		return false
+	}
+	return fi.IsDirectory()
+}
+
+// HasPkg returns whether the given package's
+// object file can be found inside this Tree.
+func (t *Tree) HasPkg(pkg string) bool {
+	fi, err := os.Stat(filepath.Join(t.PkgDir(), pkg+".a"))
+	if err != nil {
+		return false
+	}
+	return fi.IsRegular()
+	// TODO(adg): check object version is consistent
+}
+
+var (
+	ErrNotFound     = os.NewError("go/build: package could not be found locally")
+	ErrTreeNotFound = os.NewError("go/build: no valid GOROOT or GOPATH could be found")
+)
+
+// FindTree takes an import or filesystem path and returns the
+// tree where the package source should be and the package import path.
+func FindTree(path string) (tree *Tree, pkg string, err os.Error) {
+	if isLocalPath(path) {
+		if path, err = filepath.Abs(path); err != nil {
+			return
+		}
+		if path, err = filepath.EvalSymlinks(path); err != nil {
+			return
+		}
+		for _, t := range Path {
+			tpath := t.SrcDir() + string(filepath.Separator)
+			if !filepath.HasPrefix(path, tpath) {
+				continue
+			}
+			tree = t
+			pkg = path[len(tpath):]
+			return
+		}
+		err = fmt.Errorf("path %q not inside a GOPATH", path)
+		return
+	}
+	tree = defaultTree
+	pkg = path
+	for _, t := range Path {
+		if t.HasSrc(pkg) {
+			tree = t
+			return
+		}
+	}
+	if tree == nil {
+		err = ErrTreeNotFound
+	} else {
+		err = ErrNotFound
+	}
+	return
+}
+
+// isLocalPath returns whether the given path is local (/foo ./foo ../foo . ..)
+// Windows paths that starts with drive letter (c:\foo c:foo) are considered local.
+func isLocalPath(s string) bool {
+	const sep = string(filepath.Separator)
+	return s == "." || s == ".." ||
+		filepath.HasPrefix(s, sep) ||
+		filepath.HasPrefix(s, "."+sep) || filepath.HasPrefix(s, ".."+sep) ||
+		filepath.VolumeName(s) != ""
+}
+
+var (
+	// argument lists used by the build's gc and ld methods
+	gcImportArgs []string
+	ldImportArgs []string
+
+	// default tree for remote packages
+	defaultTree *Tree
+)
+
+// set up Path: parse and validate GOROOT and GOPATH variables
+func init() {
+	root := runtime.GOROOT()
+	t, err := newTree(root)
+	if err != nil {
+		log.Printf("go/build: invalid GOROOT %q: %v", root, err)
+	} else {
+		t.Goroot = true
+		Path = []*Tree{t}
+	}
+
+	for _, p := range filepath.SplitList(os.Getenv("GOPATH")) {
+		if p == "" {
+			continue
+		}
+		t, err := newTree(p)
+		if err != nil {
+			log.Printf("go/build: invalid GOPATH %q: %v", p, err)
+			continue
+		}
+		Path = append(Path, t)
+		gcImportArgs = append(gcImportArgs, "-I", t.PkgDir())
+		ldImportArgs = append(ldImportArgs, "-L", t.PkgDir())
+
+		// select first GOPATH entry as default
+		if defaultTree == nil {
+			defaultTree = t
+		}
+	}
+
+	// use GOROOT if no valid GOPATH specified
+	if defaultTree == nil && len(Path) > 0 {
+		defaultTree = Path[0]
+	}
+}
diff --git a/src/pkg/go/build/pkgtest/pkgtest.go b/src/pkg/go/build/pkgtest/pkgtest.go
new file mode 100644
index 000000000..9322f5ebd
--- /dev/null
+++ b/src/pkg/go/build/pkgtest/pkgtest.go
@@ -0,0 +1,9 @@
+// Copyright 2011 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 pkgtest
+
+func Foo() {}
+
+func Sqrt(x float64) float64
diff --git a/src/pkg/go/build/pkgtest/sqrt_386.s b/src/pkg/go/build/pkgtest/sqrt_386.s
new file mode 100644
index 000000000..d0a428d52
--- /dev/null
+++ b/src/pkg/go/build/pkgtest/sqrt_386.s
@@ -0,0 +1,10 @@
+// Copyright 2009 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.
+
+// func Sqrt(x float64) float64	
+TEXT ·Sqrt(SB),7,$0
+	FMOVD   x+0(FP),F0
+	FSQRT
+	FMOVDP  F0,r+8(FP)
+	RET
diff --git a/src/pkg/go/build/pkgtest/sqrt_amd64.s b/src/pkg/go/build/pkgtest/sqrt_amd64.s
new file mode 100644
index 000000000..f5b329e70
--- /dev/null
+++ b/src/pkg/go/build/pkgtest/sqrt_amd64.s
@@ -0,0 +1,9 @@
+// Copyright 2009 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.
+
+// func Sqrt(x float64) float64
+TEXT ·Sqrt(SB),7,$0
+	SQRTSD x+0(FP), X0
+	MOVSD X0, r+8(FP)
+	RET
diff --git a/src/pkg/go/build/pkgtest/sqrt_arm.s b/src/pkg/go/build/pkgtest/sqrt_arm.s
new file mode 100644
index 000000000..befbb8a89
--- /dev/null
+++ b/src/pkg/go/build/pkgtest/sqrt_arm.s
@@ -0,0 +1,10 @@
+// Copyright 2011 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.
+
+// func Sqrt(x float64) float64	
+TEXT ·Sqrt(SB),7,$0
+	MOVD   x+0(FP),F0
+	SQRTD  F0,F0
+	MOVD  F0,r+8(FP)
+	RET
diff --git a/src/pkg/go/build/syslist_test.go b/src/pkg/go/build/syslist_test.go
new file mode 100644
index 000000000..eb0e5dcb6
--- /dev/null
+++ b/src/pkg/go/build/syslist_test.go
@@ -0,0 +1,62 @@
+// Copyright 2011 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 build
+
+import (
+	"runtime"
+	"testing"
+)
+
+var (
+	thisOS    = runtime.GOOS
+	thisArch  = runtime.GOARCH
+	otherOS   = anotherOS()
+	otherArch = anotherArch()
+)
+
+func anotherOS() string {
+	if thisOS != "darwin" {
+		return "darwin"
+	}
+	return "linux"
+}
+
+func anotherArch() string {
+	if thisArch != "amd64" {
+		return "amd64"
+	}
+	return "386"
+}
+
+type GoodFileTest struct {
+	name   string
+	result bool
+}
+
+var tests = []GoodFileTest{
+	{"file.go", true},
+	{"file.c", true},
+	{"file_foo.go", true},
+	{"file_" + thisArch + ".go", true},
+	{"file_" + otherArch + ".go", false},
+	{"file_" + thisOS + ".go", true},
+	{"file_" + otherOS + ".go", false},
+	{"file_" + thisOS + "_" + thisArch + ".go", true},
+	{"file_" + otherOS + "_" + thisArch + ".go", false},
+	{"file_" + thisOS + "_" + otherArch + ".go", false},
+	{"file_" + otherOS + "_" + otherArch + ".go", false},
+	{"file_foo_" + thisArch + ".go", true},
+	{"file_foo_" + otherArch + ".go", false},
+	{"file_" + thisOS + ".c", true},
+	{"file_" + otherOS + ".c", false},
+}
+
+func TestGoodOSArch(t *testing.T) {
+	for _, test := range tests {
+		if goodOSArch(test.name) != test.result {
+			t.Fatalf("goodOSArch(%q) != %v", test.name, test.result)
+		}
+	}
+}