os: make the system info a value not a pointer on unix

fix a couple of other minor related details.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5690071

src/pkg/os/exec_plan9.go

@@ -66,7 +66,7 @@ func (p *Process) Kill() error {
 }
 
 // Wait waits for the Process to exit or stop, and then returns a
-// Waitmsg describing its status and an error, if any.
+// ProcessState describing its status and an error, if any.
 func (p *Process) Wait() (ps *ProcessState, err error) {
 	var waitmsg syscall.Waitmsg
 
@@ -89,7 +89,7 @@ func (p *Process) Wait() (ps *ProcessState, err error) {
 
 	ps = &ProcessState{
 		pid:    waitmsg.Pid,
-		status: waitmsg,
+		status: &waitmsg,
 	}
 	return ps, nil
 }
@@ -110,8 +110,8 @@ func findProcess(pid int) (p *Process, err error) {
 
 // ProcessState stores information about process as reported by Wait.
 type ProcessState struct {
-	pid    int             // The process's id.
-	status syscall.Waitmsg // System-dependent status info.
+	pid    int              // The process's id.
+	status *syscall.Waitmsg // System-dependent status info.
 }
 
 // Pid returns the process id of the exited process.
@@ -134,14 +134,14 @@ func (p *ProcessState) Success() bool {
 // the process.  Convert it to the appropriate underlying
 // type, such as *syscall.Waitmsg on Plan 9, to access its contents.
 func (p *ProcessState) Sys() interface{} {
-	return &p.status
+	return p.status
 }
 
 // SysUsage returns system-dependent resource usage information about
 // the exited process.  Convert it to the appropriate underlying
-// type, such as *syscall.Waitmsg on Unix, to access its contents.
+// type, such as *syscall.Waitmsg on Plan 9, to access its contents.
 func (p *ProcessState) SysUsage() interface{} {
-	return &p.status
+	return p.status
 }
 
 // UserTime returns the user CPU time of the exited process and its children.

src/pkg/os/exec_posix.go

@@ -44,8 +44,8 @@ func (p *Process) Kill() error {
 
 // ProcessState stores information about process as reported by Wait.
 type ProcessState struct {
-	pid    int                 // The process's id.
-	status *syscall.WaitStatus // System-dependent status info.
+	pid    int                // The process's id.
+	status syscall.WaitStatus // System-dependent status info.
 	rusage *syscall.Rusage
 }
 
@@ -67,7 +67,7 @@ func (p *ProcessState) Success() bool {
 
 // Sys returns system-dependent exit information about
 // the process.  Convert it to the appropriate underlying
-// type, such as *syscall.WaitStatus on Unix, to access its contents.
+// type, such as syscall.WaitStatus on Unix, to access its contents.
 func (p *ProcessState) Sys() interface{} {
 	return p.status
 }
@@ -110,7 +110,7 @@ func (p *ProcessState) String() string {
 	if p == nil {
 		return "<nil>"
 	}
-	status := p.Sys().(*syscall.WaitStatus)
+	status := p.Sys().(syscall.WaitStatus)
 	res := ""
 	switch {
 	case status.Exited():

src/pkg/os/exec_unix.go

@@ -30,7 +30,7 @@ func (p *Process) Wait() (ps *ProcessState, err error) {
 	}
 	ps = &ProcessState{
 		pid:    pid1,
-		status: &status,
+		status: status,
 		rusage: &rusage,
 	}
 	return ps, nil

src/pkg/os/exec_windows.go

@@ -30,7 +30,7 @@ func (p *Process) Wait() (ps *ProcessState, err error) {
 		return nil, NewSyscallError("GetExitCodeProcess", e)
 	}
 	p.done = true
-	return &ProcessState{p.Pid, &syscall.WaitStatus{Status: s, ExitCode: ec}, new(syscall.Rusage)}, nil
+	return &ProcessState{p.Pid, syscall.WaitStatus{Status: s, ExitCode: ec}, new(syscall.Rusage)}, nil
 }
 
 // Signal sends a signal to the Process.