buf fix: make FD.Read, FD.Write work for empty buffers

R=r
DELTA=8  (6 added, 0 deleted, 2 changed)
OCL=19273
CL=19275

diff --git a/src/lib/os/os_file.go b/src/lib/os/os_file.go
index ee4deef72a7c55b18c60ebd4188507ce8a7e48a0..2667a1e21296c7078c453ee4bd8029fcae72d1c8 100644 (file)
--- a/src/lib/os/os_file.go
+++ b/src/lib/os/os_file.go
@@ -57,7 +57,10 @@ func (fd *FD) Read(b *[]byte) (ret int, err *Error) {
        if fd == nil {
                return -1, EINVAL
        }
-       r, e := syscall.read(fd.fd, &b[0], int64(len(b)));
+       var r, e int64;
+       if len(b) > 0 {  // because we access b[0]
+               r, e = syscall.read(fd.fd, &b[0], int64(len(b)));
+       }
        return int(r), ErrnoToError(e)
 }
 
@@ -65,7 +68,10 @@ func (fd *FD) Write(b *[]byte) (ret int, err *Error) {
        if fd == nil {
                return -1, EINVAL
        }
-       r, e := syscall.write(fd.fd, &b[0], int64(len(b)));
+       var r, e int64;
+       if len(b) > 0 {  // because we access b[0]
+               r, e = syscall.write(fd.fd, &b[0], int64(len(b)));
+       }
        return int(r), ErrnoToError(e)
 }