localedef: Add tests-container test for --no-hard-links.

diff --git a/localedata/Makefile b/localedata/Makefile
index e89bacc1aa..ccfcb0049f 100644
--- a/localedata/Makefile
+++ b/localedata/Makefile
@@ -167,6 +167,8 @@  tests-special += $(objpfx)mtrace-tst-leaks.out
 endif
 endif
 endif
+tests-container = \
+			tst-localedef-hardlinks
 
 # Files to install.
 ifeq ($(INSTALL_UNCOMPRESSED),yes)
diff --git a/localedata/tst-localedef-hardlinks.c b/localedata/tst-localedef-hardlinks.c
new file mode 100644
index 0000000000..672a03ad45
--- /dev/null
+++ b/localedata/tst-localedef-hardlinks.c
@@ -0,0 +1,130 @@ 
+/* Test --no-hard-links option to localedef.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* The test is designed to run in a container and execute localedef
+   once without --no-hard-links, verify that there are 2 hard links to
+   LC_CTYPE, and then run again *with* --no-hard-links and verify there
+   are no hard links and link counts remain at 1.  The expectation here
+   is that LC_CTYPE is identical for both locales because they are same
+   empty locale but with a different name.  We use tests-container in
+   this test because the hard link optimziation is only carried out for
+   the default locale installation directory, and to write to that we
+   need write access to that directory, enabled by 'su' via
+   tests-container framework.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xunistd.h>
+#include <support/capture_subprocess.h>
+
+/* Each test compiles a locale to output, and has an expected link count for
+   LC_CTYPE.  */
+struct test_data
+{
+  /* Arguments to localedef for this step.  */
+  const char * argv[16];
+  /* Expected output file generated by running localedef.  */
+  const char *output;
+  /* Expected st_nlink count for the output.  */
+  int st_nlink;
+};
+
+/* Check for link count.  */
+void
+check_link (struct test_data step)
+{
+  struct stat64 locale;
+  char *output;
+
+  output = xasprintf ("%s/%s", support_complocaledir_prefix, step.output);
+  xstat (output, &locale);
+  free (output);
+  TEST_COMPARE (locale.st_nlink, step.st_nlink);
+}
+
+static void
+run_localedef (void *step)
+{
+  const char *prog = xasprintf ("%s/localedef", support_bindir_prefix);
+  struct test_data *one = (struct test_data *) step;
+
+  one->argv[0] = prog;
+  execv (prog, (char * const *) one->argv);
+  FAIL_EXIT1 ("execv: %m");
+}
+
+#define TEST1DIR "test1_locale.dir"
+#define TEST2DIR "test2_locale.dir"
+
+/* The whole test has 4 steps described below.  */
+static struct test_data step[4] = {
+  { .argv = { NULL, "--no-archive", "-i", "/test1_locale", TEST1DIR, NULL },
+    .output = TEST1DIR "/LC_CTYPE",
+    .st_nlink = 1 },
+  { .argv = { NULL, "--no-archive", "-i", "/test2_locale", TEST2DIR, NULL },
+    .output = TEST2DIR "/LC_CTYPE",
+    .st_nlink = 2 },
+  { .argv = { NULL, "--no-archive", "--no-hard-links", "-i", "/test1_locale",
+	      TEST1DIR, NULL },
+    .output = TEST1DIR "/LC_CTYPE",
+    .st_nlink = 1 },
+  { .argv = { NULL, "--no-archive", "--no-hard-links", "-i", "/test2_locale",
+	      TEST1DIR, NULL },
+    .output = TEST2DIR "/LC_CTYPE",
+    .st_nlink = 1 },
+};
+
+static int
+do_test (void)
+{
+  struct support_capture_subprocess result;
+
+  printf ("INFO: $complocaledir is %s\n", support_complocaledir_prefix);
+  /* Compile the first locale.  */
+  result = support_capture_subprocess (run_localedef, (void *) &step[0]);
+  support_capture_subprocess_check (&result, "execv", 1, sc_allow_stderr);
+  check_link (step[0]);
+
+  /* This time around we should have link counts of 2 for the second
+     linked locale since categories are identical.  */
+  result = support_capture_subprocess (run_localedef, (void *) &step[1]);
+  support_capture_subprocess_check (&result, "execv", 1, sc_allow_stderr);
+  check_link (step[1]);
+
+  /* Again with --no-hard-links (link count is always one).  */
+  result = support_capture_subprocess (run_localedef, (void *) &step[2]);
+  support_capture_subprocess_check (&result, "execv", 1, sc_allow_stderr);
+  check_link (step[2]);
+
+  /* Again with --no-hard-links, and the link count must remain 1.  */
+  result = support_capture_subprocess (run_localedef, (void *) &step[3]);
+  support_capture_subprocess_check (&result, "execv", 1, sc_allow_stderr);
+  check_link (step[3]);
+
+  /* Tested without and with --no-hard-links and link counts were
+     consistent.  */
+  return EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
diff --git a/localedata/tst-localedef-hardlinks.root/postclean.req b/localedata/tst-localedef-hardlinks.root/postclean.req
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/localedata/tst-localedef-hardlinks.root/test1_locale b/localedata/tst-localedef-hardlinks.root/test1_locale
new file mode 100644
index 0000000000..79f4c3aec4
--- /dev/null
+++ b/localedata/tst-localedef-hardlinks.root/test1_locale
@@ -0,0 +1,3 @@ 
+comment_char %
+escape_char /
+% Empty test locale.  Must be identical to the other test locale.
diff --git a/localedata/tst-localedef-hardlinks.root/test2_locale b/localedata/tst-localedef-hardlinks.root/test2_locale
new file mode 100644
index 0000000000..79f4c3aec4
--- /dev/null
+++ b/localedata/tst-localedef-hardlinks.root/test2_locale
@@ -0,0 +1,3 @@ 
+comment_char %
+escape_char /
+% Empty test locale.  Must be identical to the other test locale.
diff --git a/localedata/tst-localedef-hardlinks.root/tst-localedef-hardlinks.script b/localedata/tst-localedef-hardlinks.root/tst-localedef-hardlinks.script
new file mode 100644
index 0000000000..7c737aceb0
--- /dev/null
+++ b/localedata/tst-localedef-hardlinks.root/tst-localedef-hardlinks.script
@@ -0,0 +1,10 @@ 
+# Need root to write to $complocaledir when running localedef.
+su
+
+# The container install ensures we have uncompressed charmaps so we don't
+# need gzip, and we don't need to copy in the uncompressed charmap from
+# the source tree.
+
+# We need to create all the parent directories to install the locales
+# into.
+mkdirp 0755 $complocaledir/