lib: add fileutils file with stream error checking facility

The close_stream() is copied from GNU lib. Inspiration to do this
is talk by Jim Meyering - Goodbye World! The perils of relying on
output streams in C.

Reference: http://www.irill.org/events/ghm-gnu-hackers-meeting/videos/jim-meyering-goodbye-world-the-perils-of-relying-on-output-streams-in-c
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

include/fileutils.h

@@ -0,0 +1,7 @@
+#ifndef PROCPS_NG_FILEUTILS
+#define PROCPS_NG_FILEUTILS
+
+int close_stream(FILE * stream);
+void close_stdout(void);
+
+#endif

lib/.gitignore

@@ -1,2 +1,3 @@
 .dirstamp
+test_fileutils
 test_strutils

lib/Makefile.am

@@ -2,6 +2,7 @@ AM_CPPFLAGS = -include $(top_builddir)/config.h -I$(top_srcdir)/include
 
 AM_CPPFLAGS += -DTEST_PROGRAM
 
-noinst_PROGRAMS = test_strutils
+noinst_PROGRAMS = test_strutils test_fileutils
 
 test_strutils_SOURCES = strutils.c
+test_fileutils_SOURCES = fileutils.c

lib/fileutils.c

@@ -0,0 +1,43 @@
+#include <errno.h>
+#include <error.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "nls.h"
+
+int close_stream(FILE * stream)
+{
+	const int some_pending = (__fpending(stream) != 0);
+	const int prev_fail = (ferror(stream) != 0);
+	const int fclose_fail = (fclose(stream) != 0);
+	if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) {
+		if (!fclose_fail)
+			errno = 0;
+		return EOF;
+	}
+	return 0;
+}
+
+/* Use atexit(); */
+void close_stdout(void)
+{
+	if (close_stream(stdout) != 0 && !(errno == EPIPE)) {
+		char const *write_error = _("write error");
+		error(0, errno, "%s", write_error);
+		_exit(EXIT_FAILURE);
+	}
+
+	if (close_stream(stderr) != 0)
+		_exit(EXIT_FAILURE);
+}
+
+#ifdef TEST_PROGRAM
+#include <stdio.h>
+int main(int argc, char *argv[])
+{
+	atexit(close_stdout);
+	printf("Hello, World!\n");
+	return EXIT_SUCCESS;
+}
+#endif				/* TEST_PROGRAM */

testsuite/Makefile.am

@@ -34,6 +34,7 @@ EXTRA_DIST = \
 	global-conf.exp \
     free.test/free.exp \
     kill.test/kill.exp \
+    lib.test/fileutils.exp \
     lib.test/strutils.exp \
     pgrep.test/pgrep.exp \
     pkill.test/pkill.exp \

testsuite/lib.test/fileutils.exp

@@ -0,0 +1,19 @@
+#
+# Testsuite for lib/fileutils program
+#
+
+set noarg "${topdir}lib/test_fileutils"
+
+set test "without argument"
+spawn $noarg
+expect_pass "$test" "Hello, World!"
+
+set badfd "${topdir}testsuite/lib.test/fileutils_badfd.sh"
+set test "test bad file descriptor"
+spawn $badfd
+expect_pass "$test" "test_fileutils: write error: Bad file descriptor"
+
+set full "${topdir}testsuite/lib.test/fileutils_full.sh"
+set test "test no space left on device"
+spawn $full
+expect_pass "$test" "test_fileutils: write error: No space left on device"

testsuite/lib.test/fileutils_badfd.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+BASEDIR=$(dirname ${0})
+${BASEDIR}/../../lib/test_fileutils >&-

testsuite/lib.test/fileutils_full.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+BASEDIR=$(dirname ${0})
+${BASEDIR}/../../lib/test_fileutils > /dev/full