Fix data-loss with --batch.

* admin/merge-gnulib (GNULIB_MODULES): Add close-stream.
* lib/close-stream.c, lib/close-stream.h, lib/fpending.c
* lib/fpending.h, m4/close-stream.m4, m4/fpending.m4:
New files, from gnulib.
* lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate.
* src/emacs.c: Include <close-stream.h>.
(close_output_streams): New function.
(main): Pass it to atexit, so that Emacs closes stdout and stderr
and handles errors appropriately.
(Fkill_emacs): Don't worry about flushing, as close_output_stream
does that now.

Fixes: debbugs:9574

5 files changed, 158 insertions, 1 deletions

diff --git a/lib/close-stream.c b/lib/close-stream.c
new file mode 100644
index 00000000000..04fa5ece09d
--- /dev/null
+++ b/lib/close-stream.c
@@ -0,0 +1,78 @@
+/* Close a stream, with nicer error checking than fclose's.
+
+   Copyright (C) 1998-2002, 2004, 2006-2012 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/>.  */
+
+#include <config.h>
+
+#include "close-stream.h"
+
+#include <errno.h>
+#include <stdbool.h>
+
+#include "fpending.h"
+
+#if USE_UNLOCKED_IO
+# include "unlocked-io.h"
+#endif
+
+/* Close STREAM.  Return 0 if successful, EOF (setting errno)
+   otherwise.  A failure might set errno to 0 if the error number
+   cannot be determined.
+
+   A failure with errno set to EPIPE may or may not indicate an error
+   situation worth signaling to the user.  See the documentation of the
+   close_stdout_set_ignore_EPIPE function for details.
+
+   If a program writes *anything* to STREAM, that program should close
+   STREAM and make sure that it succeeds before exiting.  Otherwise,
+   suppose that you go to the extreme of checking the return status
+   of every function that does an explicit write to STREAM.  The last
+   printf can succeed in writing to the internal stream buffer, and yet
+   the fclose(STREAM) could still fail (due e.g., to a disk full error)
+   when it tries to write out that buffered data.  Thus, you would be
+   left with an incomplete output file and the offending program would
+   exit successfully.  Even calling fflush is not always sufficient,
+   since some file systems (NFS and CODA) buffer written/flushed data
+   until an actual close call.
+
+   Besides, it's wasteful to check the return value from every call
+   that writes to STREAM -- just let the internal stream state record
+   the failure.  That's what the ferror test is checking below.  */
+
+int
+close_stream (FILE *stream)
+{
+  const bool some_pending = (__fpending (stream) != 0);
+  const bool prev_fail = (ferror (stream) != 0);
+  const bool fclose_fail = (fclose (stream) != 0);
+
+  /* Return an error indication if there was a previous failure or if
+     fclose failed, with one exception: ignore an fclose failure if
+     there was no previous error, no data remains to be flushed, and
+     fclose failed with EBADF.  That can happen when a program like cp
+     is invoked like this 'cp a b >&-' (i.e., with standard output
+     closed) and doesn't generate any output (hence no previous error
+     and nothing to be flushed).  */
+
+  if (prev_fail || (fclose_fail && (some_pending || errno != EBADF)))
+    {
+      if (! fclose_fail)
+        errno = 0;
+      return EOF;
+    }
+
+  return 0;
+}
diff --git a/lib/close-stream.h b/lib/close-stream.h
new file mode 100644
index 00000000000..be3d4196b06
--- /dev/null
+++ b/lib/close-stream.h
@@ -0,0 +1,2 @@
+#include <stdio.h>
+int close_stream (FILE *stream);
diff --git a/lib/fpending.c b/lib/fpending.c
new file mode 100644
index 00000000000..2591d534377
--- /dev/null
+++ b/lib/fpending.c
@@ -0,0 +1,30 @@
+/* fpending.c -- return the number of pending output bytes on a stream
+   Copyright (C) 2000, 2004, 2006-2007, 2009-2012 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/>.  */
+
+/* Written by Jim Meyering. */
+
+#include <config.h>
+
+#include "fpending.h"
+
+/* Return the number of pending (aka buffered, unflushed)
+   bytes on the stream, FP, that is open for writing.  */
+size_t
+__fpending (FILE *fp)
+{
+  return PENDING_OUTPUT_N_BYTES;
+}
diff --git a/lib/fpending.h b/lib/fpending.h
new file mode 100644
index 00000000000..0365287ba76
--- /dev/null
+++ b/lib/fpending.h
@@ -0,0 +1,30 @@
+/* Declare __fpending.
+
+   Copyright (C) 2000, 2003, 2005-2006, 2009-2012 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/>.
+
+   Written by Jim Meyering.  */
+
+#include <stddef.h>
+#include <stdio.h>
+
+#if HAVE_DECL___FPENDING
+# if HAVE_STDIO_EXT_H
+#  include <stdio_ext.h>
+# endif
+#else
+size_t __fpending (FILE *);
+#endif
diff --git a/lib/gnulib.mk b/lib/gnulib.mk
index 23749331a83..324e5cb78fd 100644
--- a/lib/gnulib.mk
+++ b/lib/gnulib.mk
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=errno --avoid=fcntl --avoid=fcntl-h --avoid=fstat --avoid=msvc-inval --avoid=msvc-nothrow --avoid=raise --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo filemode getloadavg getopt-gnu gettime gettimeofday ignore-value intprops largefile lstat manywarnings mktime pselect pthread_sigmask readlink socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub utimens warnings
+# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=errno --avoid=fcntl --avoid=fcntl-h --avoid=fstat --avoid=msvc-inval --avoid=msvc-nothrow --avoid=raise --avoid=select --avoid=sigprocmask --avoid=sys_types --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt c-ctype c-strcase careadlinkat close-stream crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo filemode getloadavg getopt-gnu gettime gettimeofday ignore-value intprops largefile lstat manywarnings mktime pselect pthread_sigmask readlink socklen stat-time stdalign stdarg stdbool stdio strftime strtoimax strtoumax symlink sys_stat sys_time time timer-time timespec-add timespec-sub utimens warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -84,6 +84,14 @@ EXTRA_DIST += careadlinkat.h
 
 ## end   gnulib module careadlinkat
 
+## begin gnulib module close-stream
+
+libgnu_a_SOURCES += close-stream.c
+
+EXTRA_DIST += close-stream.h
+
+## end   gnulib module close-stream
+
 ## begin gnulib module crypto/md5
 
 libgnu_a_SOURCES += md5.c
@@ -183,6 +191,15 @@ EXTRA_DIST += filemode.h
 
 ## end   gnulib module filemode
 
+## begin gnulib module fpending
+
+
+EXTRA_DIST += fpending.c fpending.h
+
+EXTRA_libgnu_a_SOURCES += fpending.c
+
+## end   gnulib module fpending
+
 ## begin gnulib module getloadavg