os/exec: recombine goroutinePipes and userPipes

This change undoes CL 401894, because on further consideration
it turns out not to be needed.

This also makes (*Cmd).closeDescriptors a free function, since it does
not actually use the receiver in any way and is not needed to satisfy
any interfaces.

For #50436.

Change-Id: I7915265b0e6398ed5a34fae0c12873ab08a14194
Reviewed-on: https://go-review.googlesource.com/c/go/+/437175
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>

1 files changed, 15 insertions, 25 deletions

diff --git a/src/os/exec/exec.go b/src/os/exec/exec.go
index 074c429657..8e6f709a2f 100644
--- a/src/os/exec/exec.go
+++ b/src/os/exec/exec.go
@@ -226,17 +226,11 @@ type Cmd struct {
 	// are inherited by the child process.
 	childIOFiles []io.Closer
 
-	// goroutinePipes holds closers for the parent's end of any pipes
+	// parentIOPipes holds closers for the parent's end of any pipes
 	// connected to the child's stdin, stdout, and/or stderr streams
-	// that are pumped (and ultimately closed) by goroutines controlled by
-	// the Cmd itself (not supplied by or returned to the caller).
-	goroutinePipes []io.Closer
-
-	// userPipes holds closers for the parent's end of any pipes
-	// connected to the child's stdin, stdout and/or stderr streams
-	// that were opened and returned by the Cmd's Pipe methods.
-	// These should be closed when Wait completes.
-	userPipes []io.Closer
+	// that were opened by the Cmd itself (not supplied by the caller).
+	// These should be closed after Wait sees the command exit.
+	parentIOPipes []io.Closer
 
 	// goroutine holds a set of closures to execute to copy data
 	// to and/or from the command's I/O pipes.
@@ -380,7 +374,7 @@ func (c *Cmd) childStdin() (*os.File, error) {
 	}
 
 	c.childIOFiles = append(c.childIOFiles, pr)
-	c.goroutinePipes = append(c.goroutinePipes, pw)
+	c.parentIOPipes = append(c.parentIOPipes, pw)
 	c.goroutine = append(c.goroutine, func() error {
 		_, err := io.Copy(pw, c.Stdin)
 		if skipStdinCopyError(err) {
@@ -429,7 +423,7 @@ func (c *Cmd) writerDescriptor(w io.Writer) (*os.File, error) {
 	}
 
 	c.childIOFiles = append(c.childIOFiles, pw)
-	c.goroutinePipes = append(c.goroutinePipes, pr)
+	c.parentIOPipes = append(c.parentIOPipes, pr)
 	c.goroutine = append(c.goroutine, func() error {
 		_, err := io.Copy(w, pr)
 		pr.Close() // in case io.Copy stopped due to write error
@@ -438,7 +432,7 @@ func (c *Cmd) writerDescriptor(w io.Writer) (*os.File, error) {
 	return pw, nil
 }
 
-func (c *Cmd) closeDescriptors(closers []io.Closer) {
+func closeDescriptors(closers []io.Closer) {
 	for _, fd := range closers {
 		fd.Close()
 	}
@@ -505,14 +499,12 @@ func (c *Cmd) Start() error {
 
 	started := false
 	defer func() {
-		c.closeDescriptors(c.childIOFiles)
+		closeDescriptors(c.childIOFiles)
 		c.childIOFiles = nil
 
 		if !started {
-			c.closeDescriptors(c.goroutinePipes)
-			c.goroutinePipes = nil
-			c.closeDescriptors(c.userPipes)
-			c.userPipes = nil
+			closeDescriptors(c.parentIOPipes)
+			c.parentIOPipes = nil
 		}
 	}()
 
@@ -709,10 +701,8 @@ func (c *Cmd) Wait() error {
 			err = copyErr
 		}
 	}
-	c.goroutinePipes = nil // Already closed by their respective goroutines.
-
-	c.closeDescriptors(c.userPipes)
-	c.userPipes = nil
+	closeDescriptors(c.parentIOPipes)
+	c.parentIOPipes = nil
 
 	return err
 }
@@ -777,7 +767,7 @@ func (c *Cmd) StdinPipe() (io.WriteCloser, error) {
 	c.Stdin = pr
 	c.childIOFiles = append(c.childIOFiles, pr)
 	wc := &closeOnce{File: pw}
-	c.userPipes = append(c.userPipes, wc)
+	c.parentIOPipes = append(c.parentIOPipes, wc)
 	return wc, nil
 }
 
@@ -818,7 +808,7 @@ func (c *Cmd) StdoutPipe() (io.ReadCloser, error) {
 	}
 	c.Stdout = pw
 	c.childIOFiles = append(c.childIOFiles, pw)
-	c.userPipes = append(c.userPipes, pr)
+	c.parentIOPipes = append(c.parentIOPipes, pr)
 	return pr, nil
 }
 
@@ -843,7 +833,7 @@ func (c *Cmd) StderrPipe() (io.ReadCloser, error) {
 	}
 	c.Stderr = pw
 	c.childIOFiles = append(c.childIOFiles, pw)
-	c.userPipes = append(c.userPipes, pr)
+	c.parentIOPipes = append(c.parentIOPipes, pr)
 	return pr, nil
 }