runtime: allow arbitrary return type in SetFinalizer.

	finalize chan, to free OS X semaphore inside Lock.
os: finalize File, to close fd.

Fixes issue 503.

R=ken2
CC=golang-dev
http://codereview.appspot.com/204065

1 files changed, 5 insertions, 2 deletions

diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
index b92384e2c..83b022aa0 100644
--- a/src/pkg/os/file.go
+++ b/src/pkg/os/file.go
@@ -7,6 +7,7 @@
 package os
 
 import (
+	"runtime"
 	"syscall"
 )
 
@@ -36,7 +37,9 @@ func NewFile(fd int, name string) *File {
 	if fd < 0 {
 		return nil
 	}
-	return &File{fd, name, nil, 0}
+	f := &File{fd, name, nil, 0}
+	runtime.SetFinalizer(f, (*File).Close)
+	return f
 }
 
 // Stdin, Stdout, and Stderr are open Files pointing to the standard input,
@@ -86,7 +89,7 @@ func Open(name string, flag int, perm int) (file *File, err Error) {
 // Close closes the File, rendering it unusable for I/O.
 // It returns an Error, if any.
 func (file *File) Close() Error {
-	if file == nil {
+	if file == nil || file.fd < 0 {
 		return EINVAL
 	}
 	var err Error