fix infinite loop in Readdirnames: bufp > nbuf can happen

after EOF has been hit, because nbuf is now 0 or -1.

discard old comment.

R=r
DELTA=3  (0 added, 0 deleted, 3 changed)
OCL=27463
CL=27465

src/lib/os/dir_amd64_darwin.go

@@ -31,7 +31,7 @@ func readdirnames(file *File, count int) (names []string, err *os.Error) {
 	names = make([]string, 0, size);	// Empty with room to grow.
 	for count != 0 {
 		// Refill the buffer if necessary
-		if d.bufp == d.nbuf {
+		if d.bufp >= d.nbuf {
 			var errno int64;
 			// Final argument is (basep *int64) and the syscall doesn't take nil.
 			d.nbuf, errno = syscall.Getdirentries(file.fd, &d.buf[0], int64(len(d.buf)), new(int64));

src/lib/os/dir_amd64_linux.go

@@ -40,7 +40,7 @@ func readdirnames(file *File, count int) (names []string, err *os.Error) {
 	names = make([]string, 0, size);	// Empty with room to grow.
 	for count != 0 {
 		// Refill the buffer if necessary
-		if d.bufp == d.nbuf {
+		if d.bufp >= d.nbuf {
 			var errno int64;
 			dbuf := (*syscall.Dirent)(unsafe.Pointer(&d.buf[0]));
 			d.nbuf, errno = syscall.Getdents(file.fd, dbuf, int64(len(d.buf)));

src/lib/os/file.go

@@ -12,7 +12,7 @@ import (
 )
 
 // Auxiliary information if the File describes a directory
-type dirInfo struct {	// TODO(r): 6g bug means this can't be private
+type dirInfo struct {
 	buf	[]byte;	// buffer for directory I/O
 	nbuf	int64;	// length of buf; return value from Getdirentries
 	bufp	int64;	// location of next record in buf.