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

The new tst-localedef-hardlinks verifies that when compiling
two locales (with default output directory) one with
--no-hard-links and one without the option, results in the
expected behaviour.  When --no-hard-links is used the link
counts on LC_CTYPE is 1, indicating that even thoug the two
locale are identical (though different named source files and
output direcotry) the localedef did not carry out the hard
link optimization.  Then when --no-hard-links is omitted the
localedef hard link optimization is correctly carried out and
for 2 compiled locales the link count for LC_CTYPE is 2.

Reviewed-by: DJ Delorie <dj@redhat.com>

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)

localedata/tst-localedef-hardlinks.c

@@ -0,0 +1,135 @@
+/* Test --no-hard-links option to localedef.
+   Copyright (C) 2020 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
+   <https://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.  This test expects that localedef removes the existing
+   files before installing new copies of the files, and we do not
+   cleanup between localedef runs.  We can't cleanup between each pair
+   of runs since localedef must see the existing locale in order to
+   determine that space could be saved by using a hardlink.  */
+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.  Note the argv[0] NULL
+   will be filled in at runtime by run_localedef.  */
+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>

localedata/tst-localedef-hardlinks.root/postclean.req

@@ -0,0 +1,2 @@
+# We do not want test locales to remain installed for future tests so
+# we request that the testroot be cleaned after the test is complete.

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.

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.

localedata/tst-localedef-hardlinks.root/tst-localedef-hardlinks.script

@@ -0,0 +1,9 @@
+# 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.
+
+# The container install ensures we have the compiled locale dirctory
+# present for localedef to write to by default.