From 591f36004682e1adf977cb5d9f12c98b560924d7 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Mon, 6 Oct 2014 15:49:19 -0400
Subject: os: make Process.Signal 'process finished' error consistent on Unix

While we're here, fix the implementation of Release on both
Unix and Windows: Release is supposed to make Signal an error.

While we're here, make sure we never Signal pid 0.
(Don't try this at home.)

Fixes issue 7658.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews, iant
https://codereview.appspot.com/152240043
---
 src/os/exec_unix.go    | 14 +++++++++++---
 src/os/exec_windows.go |  3 +++
 2 files changed, 14 insertions(+), 3 deletions(-)

(limited to 'src/os')

diff --git a/src/os/exec_unix.go b/src/os/exec_unix.go
index 1b1e3350b..ed97f85e2 100644
--- a/src/os/exec_unix.go
+++ b/src/os/exec_unix.go
@@ -34,18 +34,26 @@ func (p *Process) wait() (ps *ProcessState, err error) {
 	return ps, nil
 }
 
+var errFinished = errors.New("os: process already finished")
+
 func (p *Process) signal(sig Signal) error {
-	if p.done() {
-		return errors.New("os: process already finished")
-	}
 	if p.Pid == -1 {
 		return errors.New("os: process already released")
 	}
+	if p.Pid == 0 {
+		return errors.New("os: process not initialized")
+	}
+	if p.done() {
+		return errFinished
+	}
 	s, ok := sig.(syscall.Signal)
 	if !ok {
 		return errors.New("os: unsupported signal type")
 	}
 	if e := syscall.Kill(p.Pid, s); e != nil {
+		if e == syscall.ESRCH {
+			return errFinished
+		}
 		return e
 	}
 	return nil
diff --git a/src/os/exec_windows.go b/src/os/exec_windows.go
index c4f3d4f85..393393b23 100644
--- a/src/os/exec_windows.go
+++ b/src/os/exec_windows.go
@@ -53,6 +53,9 @@ func terminateProcess(pid, exitcode int) error {
 }
 
 func (p *Process) signal(sig Signal) error {
+	if p.handle == uintptr(syscall.InvalidHandle) {
+		return syscall.EINVAL
+	}
 	if p.done() {
 		return errors.New("os: process already finished")
 	}
-- 
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