os: drop the Wait function and the options to Process.Wait

They are portability problems and the options are almost always zero in practice anyway.

R=golang-dev, dsymonds, r, bradfitz
CC=golang-dev
https://golang.org/cl/5688046

doc/go1.html

@@ -8,7 +8,7 @@
 
 
 <!-- Center the tables, and disable the 1995-era 3D borders -->
-<style>
+<style type="text/css">
 table { margin-left: auto; margin-right: auto; border-style: none; }
 hr { border-style: none; border-top: 1px solid black; }
 </style>
@@ -1460,9 +1460,20 @@ use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or
 <a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>.
 </p>
 
+
+<p>
+The <a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> method has
+dropped its option argument and the associated constants are gone
+from the package.
+Also, the function <code>Wait</code> is gone; only the method of
+the <code>Process</code> type persists.
+</p>
+
 <p>
 <em>Updating</em>:
-Affected code will be caught by the compiler and must be updated by hand.
+Gofix will rewrite calls to <code>os.Wait</code> with an explicit zero
+argument, dropping the argument.
+All other changes will be caught by the compiler and must be updated by hand.
 </p>
 
 <h4 id="os_fileinfo">The os.FileInfo type</h4>
@@ -1915,7 +1926,7 @@ so that exported function definitions can use types defined there.
 This has the effect of compiling the preamble multiple times, so a
 package using <code>//export</code> must not put function definitions
 or variable initializations in the C preamble.
-</p
+</p>
 
 <h2 id="releases">Packaged releases</h2>
 

doc/go1.tmpl

@@ -4,7 +4,7 @@
 {{donotedit}}
 
 <!-- Center the tables, and disable the 1995-era 3D borders -->
-<style>
+<style type="text/css">
 table { margin-left: auto; margin-right: auto; border-style: none; }
 hr { border-style: none; border-top: 1px solid black; }
 </style>
@@ -1363,9 +1363,20 @@ use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or
 <a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>.
 </p>
 
+
+<p>
+The <a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> method has
+dropped its option argument and the associated constants are gone
+from the package.
+Also, the function <code>Wait</code> is gone; only the method of
+the <code>Process</code> type persists.
+</p>
+
 <p>
 <em>Updating</em>:
-Affected code will be caught by the compiler and must be updated by hand.
+Gofix will rewrite calls to <code>os.Wait</code> with an explicit zero
+argument, dropping the argument.
+All other changes will be caught by the compiler and must be updated by hand.
 </p>
 
 <h4 id="os_fileinfo">The os.FileInfo type</h4>
@@ -1787,7 +1798,7 @@ so that exported function definitions can use types defined there.
 This has the effect of compiling the preamble multiple times, so a
 package using <code>//export</code> must not put function definitions
 or variable initializations in the C preamble.
-</p
+</p>
 
 <h2 id="releases">Packaged releases</h2>
 

src/cmd/cgo/util.go

@@ -56,7 +56,7 @@ func run(stdin []byte, argv []string) (stdout, stderr []byte, ok bool) {
 	<-c
 	<-c
 
-	w, err := p.Wait(0)
+	w, err := p.Wait()
 	if err != nil {
 		fatalf("%s", err)
 	}

src/cmd/fix/oswait.go

@@ -0,0 +1,56 @@
+// 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/ast"
+)
+
+func init() {
+	register(oswaitFix)
+}
+
+var oswaitFix = fix{
+	"oswait",
+	"2012-02-20",
+	oswait,
+	`Delete options from os.Wait. If the option is the literal 0, rewrite the call.
+
+http://codereview.appspot.com/5688046
+`,
+}
+
+func oswait(f *ast.File) bool {
+	if !imports(f, "os") {
+		return false
+	}
+
+	fixed := false
+
+	walk(f, func(n interface{}) {
+		call, ok := n.(*ast.CallExpr)
+		if !ok {
+			return
+		}
+		if !isPkgDot(call.Fun, "os", "Wait") {
+			return
+		}
+		args := call.Args
+		const warning = "call to Process.Wait must be fixed manually"
+		if len(args) != 1 {
+			// Shouldn't happen, but check.
+			warn(call.Pos(), warning)
+			return
+		}
+		if basicLit, ok := args[0].(*ast.BasicLit); !ok || basicLit.Value != "0" {
+			warn(call.Pos(), warning)
+			return
+		}
+		call.Args = nil
+		fixed = true
+	})
+
+	return fixed
+}

src/cmd/fix/oswait_test.go

@@ -0,0 +1,41 @@
+// 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
+
+func init() {
+	addTestCases(oswaitTests, oswait)
+}
+
+var oswaitTests = []testCase{
+	{
+		Name: "oswait.0",
+		In: `package main
+
+import (
+	"os"
+)
+
+func f() {
+	os.Wait()
+	os.Wait(0)
+	os.Wait(1)
+	os.Wait(A | B)
+}
+`,
+		Out: `package main
+
+import (
+	"os"
+)
+
+func f() {
+	os.Wait()
+	os.Wait()
+	os.Wait(1)
+	os.Wait(A | B)
+}
+`,
+	},
+}

src/cmd/godoc/main.go

@@ -103,7 +103,7 @@ func exec(rw http.ResponseWriter, args []string) (status int) {
 
 	var buf bytes.Buffer
 	io.Copy(&buf, r)
-	wait, err := p.Wait(0)
+	wait, err := p.Wait()
 	if err != nil {
 		os.Stderr.Write(buf.Bytes())
 		log.Printf("os.Wait(%d, 0): %v", p.Pid, err)

src/pkg/os/exec/exec.go

@@ -291,7 +291,7 @@ func (c *Cmd) Wait() error {
 		return errors.New("exec: Wait was already called")
 	}
 	c.finished = true
-	msg, err := c.Process.Wait(0)
+	msg, err := c.Process.Wait()
 	c.Waitmsg = msg
 
 	var copyError error

src/pkg/os/exec_plan9.go

@@ -70,9 +70,8 @@ type Waitmsg struct {
 }
 
 // Wait waits for the Process to exit or stop, and then returns a
-// Waitmsg describing its status and an error, if any. The options
+// Waitmsg describing its status and an error, if any.
-// (WNOHANG etc.) affect the behavior of the Wait call.
+func (p *Process) Wait() (w *Waitmsg, err error) {
-func (p *Process) Wait(options int) (w *Waitmsg, err error) {
 	var waitmsg syscall.Waitmsg
 
 	if p.Pid == -1 {
@@ -95,20 +94,6 @@ func (p *Process) Wait(options int) (w *Waitmsg, err error) {
 	return &Waitmsg{waitmsg}, nil
 }
 
-// Wait waits for process pid to exit or stop, and then returns a
-// Waitmsg describing its status and an error, if any. The options
-// (WNOHANG etc.) affect the behavior of the Wait call.
-// Wait is equivalent to calling FindProcess and then Wait
-// and Release on the result.
-func Wait(pid int, options int) (w *Waitmsg, err error) {
-	p, e := FindProcess(pid)
-	if e != nil {
-		return nil, e
-	}
-	defer p.Release()
-	return p.Wait(options)
-}
-
 // Release releases any resources associated with the Process.
 func (p *Process) Release() error {
 	// NOOP for Plan 9.

src/pkg/os/exec_posix.go

@@ -56,20 +56,6 @@ type Waitmsg struct {
 	Rusage             *syscall.Rusage // System-dependent resource usage info.
 }
 
-// Wait waits for process pid to exit or stop, and then returns a
-// Waitmsg describing its status and an error, if any. The options
-// (WNOHANG etc.) affect the behavior of the Wait call.
-// Wait is equivalent to calling FindProcess and then Wait
-// and Release on the result.
-func Wait(pid int, options int) (w *Waitmsg, err error) {
-	p, e := FindProcess(pid)
-	if e != nil {
-		return nil, e
-	}
-	defer p.Release()
-	return p.Wait(options)
-}
-
 // Convert i to decimal string.
 func itod(i int) string {
 	if i == 0 {

src/pkg/os/exec_unix.go

@@ -12,43 +12,23 @@ import (
 	"syscall"
 )
 
-// Options for Wait.
-const (
-	WNOHANG   = syscall.WNOHANG   // Don't wait if no process has exited.
-	WSTOPPED  = syscall.WSTOPPED  // If set, status of stopped subprocesses is also reported.
-	WUNTRACED = syscall.WUNTRACED // Usually an alias for WSTOPPED.
-	WRUSAGE   = 1 << 20           // Record resource usage.
-)
-
-// WRUSAGE must not be too high a bit, to avoid clashing with Linux's
-// WCLONE, WALL, and WNOTHREAD flags, which sit in the top few bits of
-// the options
-
 // Wait waits for the Process to exit or stop, and then returns a
-// Waitmsg describing its status and an error, if any. The options
+// Waitmsg describing its status and an error, if any.
-// (WNOHANG etc.) affect the behavior of the Wait call.
+func (p *Process) Wait() (w *Waitmsg, err error) {
-func (p *Process) Wait(options int) (w *Waitmsg, err error) {
 	if p.Pid == -1 {
 		return nil, syscall.EINVAL
 	}
 	var status syscall.WaitStatus
-	var rusage *syscall.Rusage
+	pid1, e := syscall.Wait4(p.Pid, &status, 0, nil)
-	if options&WRUSAGE != 0 {
-		rusage = new(syscall.Rusage)
-		options ^= WRUSAGE
-	}
-	pid1, e := syscall.Wait4(p.Pid, &status, options, rusage)
 	if e != nil {
 		return nil, NewSyscallError("wait", e)
 	}
-	// With WNOHANG pid is 0 if child has not exited.
+	if pid1 != 0 {
-	if pid1 != 0 && options&WSTOPPED == 0 {
 		p.done = true
 	}
 	w = new(Waitmsg)
 	w.Pid = pid1
 	w.WaitStatus = status
-	w.Rusage = rusage
 	return w, nil
 }
 

src/pkg/os/exec_windows.go

@@ -13,7 +13,7 @@ import (
 
 // Wait waits for the Process to exit or stop, and then returns a
 // Waitmsg describing its status and an error, if any.
-func (p *Process) Wait(options int) (w *Waitmsg, err error) {
+func (p *Process) Wait() (w *Waitmsg, err error) {
 	s, e := syscall.WaitForSingleObject(syscall.Handle(p.handle), syscall.INFINITE)
 	switch s {
 	case syscall.WAIT_OBJECT_0:

src/pkg/os/os_test.go

@@ -541,7 +541,7 @@ func exec(t *testing.T, dir, cmd string, args []string, expect string) {
 		t.Errorf("exec %q returned %q wanted %q",
 			strings.Join(append([]string{cmd}, args...), " "), output, expect)
 	}
-	p.Wait(0)
+	p.Wait()
 }
 
 func TestStartProcess(t *testing.T) {
@@ -853,7 +853,7 @@ func run(t *testing.T, cmd []string) string {
 
 	var b bytes.Buffer
 	io.Copy(&b, r)
-	_, err = p.Wait(0)
+	_, err = p.Wait()
 	if err != nil {
 		t.Fatalf("run hostname Wait: %v", err)
 	}