Re: dd and closed stderr

[Eric Blake]

Jim Meyering <jim <at> meyering.net> writes:

> Regardless of POSIX, what if an application requires that output and
> attempts to parse it?  In that case, a successful exit status is defintely
> at odds with empty stderr (which could arise also due to ENOSPC).
> 
> So I'd say it's a bug.

Here's a patch, including a testsuite addition (along with a cleanup to allow 
clean compilation on cygwin).  OK to apply?

>From 8cea0f3d5628ea3e4f74db0a66486cae5d92122a Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Fri, 28 Aug 2009 08:40:06 -0600
Subject: [PATCH 1/2] dd: detect closed stderr

* src/dd.c (maybe_close_stdout): Always flush stderr.
* tests/dd/stderr: New test, borrowing from misc/close-stdout.
* tests/Makefile.am (TESTS): Run it.
* NEWS: Mention this.
---
 NEWS              |    3 +++
 src/dd.c          |    3 +++
 tests/Makefile.am |    1 +
 tests/dd/stderr   |   47 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 54 insertions(+), 0 deletions(-)
 create mode 100755 tests/dd/stderr

diff --git a/NEWS b/NEWS
index c125b31..581620f 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,9 @@ GNU coreutils NEWS                                    -*- 
outline -*-
   due to their running on a kernel older than what was implied by headers
   and libraries tested at configure time.

+  dd now returns non-zero status if it encountered a write error while
+  printing a summary to stderr.
+

 * Noteworthy changes in release 7.5 (2009-08-20) [stable]

diff --git a/src/dd.c b/src/dd.c
index dc15cfd..c016d3d 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -25,6 +25,7 @@
 #include <getopt.h>

 #include "system.h"
+#include "close-stream.h"
 #include "error.h"
 #include "fd-reopen.h"
 #include "gethrxtime.h"
@@ -450,6 +451,8 @@ maybe_close_stdout (void)
 {
   if (close_stdout_required)
     close_stdout ();
+  else if (close_stream (stderr) != 0)
+    _exit (exit_failure);
 }

 void
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6ad6133..c88dd9c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -305,6 +305,7 @@ TESTS =                                             \
   dd/skip-seek                                 \
   dd/skip-seek2                                        \
   dd/skip-seek-past-file                       \
+  dd/stderr                                    \
   dd/unblock-sync                              \
   df/total-verify                              \
   du/2g                                                \
diff --git a/tests/dd/stderr b/tests/dd/stderr
new file mode 100755
index 0000000..46ffe48
--- /dev/null
+++ b/tests/dd/stderr
@@ -0,0 +1,47 @@
+#!/bin/sh
+# Ensure dd recognizes failure to write to stderr.
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  dd --version
+fi
+
+. $srcdir/test-lib.sh
+
+p="$abs_top_builddir"
+
+fail=0
+
+# Ensure this exits successfully, even though stderr is closed,
+# because it generates no stderr output.
+dd --help >/dev/null 2>&- || fail=1
+
+# If 2>&- works, ensure this fails, because stderr is closed and it
+# *does* generate output.  2>&- apparently does not work in HP-UX 11.23.
+# This test is ineffective unless /dev/stderr also works.
+if "$p/src/test" -w /dev/stderr 2>/dev/null &&
+   "$p/src/test" ! -w /dev/stderr 2>&-; then
+  echo | dd 2>&- && fail=1
+fi
+
+# Likewise for /dev/full, if /dev/full works.
+if test -w /dev/full && test -c /dev/full; then
+  echo | dd 2>/dev/full && fail=1
+fi
+
+Exit $fail
-- 
1.6.3.2


>From be4960b62893292b0b06abb129fca9c4c9e7f496 Mon Sep 17 00:00:00 2001
From: Eric Blake <address@hidden>
Date: Tue, 25 Aug 2009 23:40:40 -0600
Subject: [PATCH 2/2] build: avoid unused variable warnings on cygwin

* src/copy.c (clone_file, copy_attr_by_fd, copy_attr_by_name): Add
ATTRIBUTE_UNUSED.
* src/remove.c (dirent_inode_sort_may_be_useful): Likewise.
---
 src/copy.c   |   14 +++++++++-----
 src/remove.c |    5 ++++-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/copy.c b/src/copy.c
index 238764a..8176994 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -140,7 +140,7 @@ utimens_symlink (char const *file, struct timespec const 
*timespec)
 /* Perform the O(1) btrfs clone operation, if possible.
    Upon success, return 0.  Otherwise, return -1 and set errno.  */
 static inline int
-clone_file (int dest_fd, int src_fd)
+clone_file (int dest_fd ATTRIBUTE_UNUSED, int src_fd ATTRIBUTE_UNUSED)
 {
 #ifdef __linux__
 # undef BTRFS_IOCTL_MAGIC
@@ -251,15 +251,19 @@ copy_attr_by_name (char const *src_path, char const 
*dst_path,
 #else /* USE_XATTR */

 static bool
-copy_attr_by_fd (char const *src_path, int src_fd,
-                 char const *dst_path, int dst_fd, const struct cp_options *x)
+copy_attr_by_fd (char const *src_path ATTRIBUTE_UNUSED,
+                 int src_fd ATTRIBUTE_UNUSED,
+                 char const *dst_path ATTRIBUTE_UNUSED,
+                 int dst_fd ATTRIBUTE_UNUSED,
+                 const struct cp_options *x ATTRIBUTE_UNUSED)
 {
   return true;
 }

 static bool
-copy_attr_by_name (char const *src_path, char const *dst_path,
-                   const struct cp_options *x)
+copy_attr_by_name (char const *src_path ATTRIBUTE_UNUSED,
+                   char const *dst_path ATTRIBUTE_UNUSED,
+                   const struct cp_options *x ATTRIBUTE_UNUSED)
 {
   return true;
 }
diff --git a/src/remove.c b/src/remove.c
index 6c8613b..2c4a178 100644
--- a/src/remove.c
+++ b/src/remove.c
@@ -1311,7 +1311,10 @@ dirent_inode_sort_may_be_useful (int dir_fd)
     }
 }
 # else /* !HAVE_STRUCT_STATFS_F_TYPE */
-static bool dirent_inode_sort_may_be_useful (int dir_fd) { return true; }
+static bool dirent_inode_sort_may_be_useful (int dir_fd ATTRIBUTE_UNUSED)
+{
+  return true;
+}
 # endif /* !HAVE_STRUCT_STATFS_F_TYPE */
 #endif /* HAVE_STRUCT_DIRENT_D_TYPE */

-- 
1.6.3.2