os: reset dirinfo when seeking on Darwin

The first Readdirnames calls opendir and caches the result.
The behavior of that cached opendir result isn't specified on a seek
of the underlying fd. Free the opendir result on a seek so that
we'll allocate a new one the next time around.

Also fix wasm behavior in this regard, so that a seek to the
file start resets the Readdirnames position, regardless of platform.

p.s. I hate the Readdirnames API.

Fixes #35767.

Change-Id: Ieffb61b3c5cdd42591f69ab13f932003966f2297
Reviewed-on: https://go-review.googlesource.com/c/go/+/209961
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/os/dir_darwin.go b/src/os/dir_darwin.go
index 2f9ba78d680517ca315668a7c9110c4bbed2d743..a274dd126808eba7c18faf5198a40b28bcf2b547 100644 (file)
--- a/src/os/dir_darwin.go
+++ b/src/os/dir_darwin.go
@@ -24,6 +24,16 @@ func (d *dirInfo) close() {
        d.dir = 0
 }
 
+func (f *File) seekInvalidate() {
+       if f.dirinfo == nil {
+               return
+       }
+       // Free cached dirinfo, so we allocate a new one if we
+       // access this file as a directory again. See #35767.
+       f.dirinfo.close()
+       f.dirinfo = nil
+}
+
 func (f *File) readdirnames(n int) (names []string, err error) {
        if f.dirinfo == nil {
                dir, call, errno := f.pfd.OpenDir()

diff --git a/src/os/dir_unix.go b/src/os/dir_unix.go
index e0c4989756b1a0ec983d21e19241a7f2e143b439..2856a2dc0ff427556bc8b3dc2769b0cfa208d60f 100644 (file)
--- a/src/os/dir_unix.go
+++ b/src/os/dir_unix.go
@@ -26,6 +26,8 @@ const (
 
 func (d *dirInfo) close() {}
 
+func (f *File) seekInvalidate() {}
+
 func (f *File) readdirnames(n int) (names []string, err error) {
        // If this file has no dirinfo, create one.
        if f.dirinfo == nil {

diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index 31c43eb61eba97ae61c58c1f861e794b4fa0eea6..6945937fd61d0f00983fca423c6a3dc50234192c 100644 (file)
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -295,6 +295,7 @@ func (f *File) pwrite(b []byte, off int64) (n int, err error) {
 // relative to the current offset, and 2 means relative to the end.
 // It returns the new offset and an error, if any.
 func (f *File) seek(offset int64, whence int) (ret int64, err error) {
+       f.seekInvalidate()
        ret, err = f.pfd.Seek(offset, whence)
        runtime.KeepAlive(f)
        return ret, err

diff --git a/src/syscall/fs_js.go b/src/syscall/fs_js.go
index f7079e9d091d336154efd6514c7fe4f9e02cd477..16d9f58b8c4a48789ea3392107f391274a43885e 100644 (file)
--- a/src/syscall/fs_js.go
+++ b/src/syscall/fs_js.go
@@ -34,6 +34,7 @@ var (
 type jsFile struct {
        path    string
        entries []string
+       dirIdx  int // entries[:dirIdx] have already been returned in ReadDirent
        pos     int64
        seeked  bool
 }
@@ -141,8 +142,8 @@ func ReadDirent(fd int, buf []byte) (int, error) {
        }
 
        n := 0
-       for len(f.entries) > 0 {
-               entry := f.entries[0]
+       for f.dirIdx < len(f.entries) {
+               entry := f.entries[f.dirIdx]
                l := 2 + len(entry)
                if l > len(buf) {
                        break
@@ -152,7 +153,7 @@ func ReadDirent(fd int, buf []byte) (int, error) {
                copy(buf[2:], entry)
                buf = buf[l:]
                n += l
-               f.entries = f.entries[1:]
+               f.dirIdx++
        }
 
        return n, nil
@@ -470,6 +471,7 @@ func Seek(fd int, offset int64, whence int) (int64, error) {
        }
 
        f.seeked = true
+       f.dirIdx = 0 // Reset directory read position. See issue 35767.
        f.pos = newPos
        return newPos, nil
 }

diff --git a/test/fixedbugs/issue35767.go b/test/fixedbugs/issue35767.go
new file mode 100644 (file)
index 0000000..b930faa
--- /dev/null
+++ b/test/fixedbugs/issue35767.go
@@ -0,0 +1,51 @@
+// run
+
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+       "log"
+       "os"
+)
+
+func main() {
+       wd, err := os.Getwd()
+       if err != nil {
+               log.Fatal(err)
+       }
+       f, err := os.Open(wd)
+       if err != nil {
+               log.Fatal(err)
+       }
+       dirnames1, err := f.Readdirnames(0)
+       if err != nil {
+               log.Fatal(err)
+       }
+
+       ret, err := f.Seek(0, 0)
+       if err != nil {
+               log.Fatal(err)
+       }
+       if ret != 0 {
+               log.Fatalf("seek result not zero: %d", ret)
+       }
+
+       dirnames2, err := f.Readdirnames(0)
+       if err != nil {
+               log.Fatal(err)
+               return
+       }
+
+       if len(dirnames1) != len(dirnames2) {
+               log.Fatalf("listings have different lengths: %d and %d\n", len(dirnames1), len(dirnames2))
+       }
+       for i, n1 := range dirnames1 {
+               n2 := dirnames2[i]
+               if n1 != n2 {
+                       log.Fatalf("different name i=%d n1=%s n2=%s\n", i, n1, n2)
+               }
+       }
+}