[PATCH 6/6] iconv: Replace test-iconvconfig xtest with a container test

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

The old xtests-special target compared a generated cache against
$(inst_gconvdir)/gconv-modules.cache, so it required a prior make install
and only ran under make xcheck.  It also access the system gconv
configuration, which might not be in the expected place depending of how
the system configures glibc.

Run iconvconfig over the installed gconv modules inside a test-container
instead and check that cache generation succeeds and is deterministic.
---
 iconv/Makefile                                |  13 +-
 iconv/tst-iconvconfig-cache.c                 | 192 ++++++++++++++++++
 .../tst-iconvconfig-cache.root/postclean.req  |   0
 iconv/tst-iconvconfig-cache.root/preclean.req |   0
 4 files changed, 194 insertions(+), 11 deletions(-)
 create mode 100644 iconv/tst-iconvconfig-cache.c
 create mode 100644 iconv/tst-iconvconfig-cache.root/postclean.req
 create mode 100644 iconv/tst-iconvconfig-cache.root/preclean.req

diff --git a/iconv/Makefile b/iconv/Makefile
index 69555cbe579..02980457b38 100644
--- a/iconv/Makefile
+++ b/iconv/Makefile
@@ -78,8 +78,9 @@ cpp-srcs-left := $(iconv_prog-modules) $(iconvconfig-modules)
 lib := iconvprogs
 include $(patsubst %,$(..)libof-iterator.mk,$(cpp-srcs-left))
 
+tests-container += tst-iconvconfig-cache
+
 ifeq ($(run-built-tests),yes)
-xtests-special += $(objpfx)test-iconvconfig.out
 tests-special += \
 	$(objpfx)tst-iconv_prog-buffer-large.out \
 	$(objpfx)tst-iconv_prog-buffer-tiny.out \
@@ -129,16 +130,6 @@ $(inst_bindir)/iconv: $(objpfx)iconv_prog $(+force)
 $(objpfx)iconv_prog: $(iconv_prog-modules:%=$(objpfx)%.o)
 $(objpfx)iconvconfig: $(iconvconfig-modules:%=$(objpfx)%.o)
 
-$(objpfx)test-iconvconfig.out: $(objpfx)iconvconfig
-	(set -e; \
-	 tmp=$(objpfx)gconv-modules.cache.$$$$; \
-	 rm -f $$tmp; \
-	 $(run-program-prefix) $(objpfx)iconvconfig \
-		--output=$$tmp --nostdlib $(inst_gconvdir); \
-	 cmp $$tmp $(inst_gconvdir)/gconv-modules.cache; \
-	 rm -f $$tmp) > $@; \
-	$(evaluate-test)
-
 $(objpfx)tst-iconv_prog.out: tst-iconv_prog.sh $(objpfx)iconv_prog \
   $(gen-locales)
 	$(BASH) $< $(common-objdir) '$(test-wrapper-env)' \
diff --git a/iconv/tst-iconvconfig-cache.c b/iconv/tst-iconvconfig-cache.c
new file mode 100644
index 00000000000..e0d87e6654e
--- /dev/null
+++ b/iconv/tst-iconvconfig-cache.c
@@ -0,0 +1,192 @@
+/* Test that iconvconfig produces a valid, reproducible module cache.
+   Copyright (C) 2026 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/>.  */
+
+#include <fcntl.h>
+#include <iconv.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <support/capture_subprocess.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+
+#define GCONV_CACHE_MAGIC 0x20010324
+
+static char *iconvconfig;
+static char *gconvdir;
+
+static void
+run_iconvconfig (const char *out)
+{
+  char *arg_output = xasprintf ("--output=%s", out);
+  char *const argv[] =
+    {
+      iconvconfig, arg_output, (char *) "--nostdlib", gconvdir, NULL
+    };
+  struct support_capture_subprocess proc
+    = support_capture_subprogram (iconvconfig, argv, NULL);
+  support_capture_subprocess_check (&proc, "iconvconfig", 0, sc_allow_none);
+  support_capture_subprocess_free (&proc);
+  free (arg_output);
+}
+
+struct cache_file_t
+{
+  char *data;
+  size_t length;
+};
+
+static struct cache_file_t
+read_cache_file (const char *path)
+{
+  struct stat64 st;
+  xstat64 (path, &st);
+  char *buffer = xmalloc (st.st_size);
+  int fd = xopen (path, O_RDONLY, 0);
+  xread (fd, buffer, st.st_size);
+  xclose (fd);
+  return (struct cache_file_t) { buffer, st.st_size };
+}
+
+static void
+free_cache_file (struct cache_file_t *cache_file)
+{
+  free (cache_file->data);
+}
+
+static void
+write_cache_file (const char *path, const char *data, size_t length)
+{
+  int fd = xopen (path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+  xwrite (fd, data, length);
+  xclose (fd);
+}
+
+static void
+move_cache_file (const char *from, const char *to)
+{
+  if (access (from, F_OK) != 0)
+    FAIL_EXIT1 ("access(%s): %m", from);
+  if (rename (from, to) != 0)
+    FAIL_EXIT1 ("rename(%s, %s): %m", from, to);
+}
+
+static void
+check_valid_cache (const struct cache_file_t *cache_file)
+{
+  TEST_VERIFY_EXIT (cache_file->length >= sizeof (uint32_t));
+  uint32_t magic;
+  memcpy (&magic, cache_file->data, sizeof (magic));
+  TEST_COMPARE (magic, GCONV_CACHE_MAGIC);
+}
+
+/* Install the generated cache CAHCE_FILE at the canonical gconv cache path
+   and confirm that the runtime loads it and resolves a module-backed
+   conversion.  The gconv-modules text configuration is moved aside, so the
+   conversion can only succeed if it is satisfied from the cache.  A corrupt
+   cache would make the loader fall back to the missing text configuration
+   and the conversion would fail.  */
+static void
+check_loadable_cache (const struct cache_file_t *cache_file)
+{
+  char *cache = xasprintf ("%s/gconv-modules.cache", gconvdir);
+  char *conf = xasprintf ("%s/gconv-modules", gconvdir);
+  char *confd = xasprintf ("%s/gconv-modules.d", gconvdir);
+  char *conf_bak = xasprintf ("%s.disabled", conf);
+  char *confd_bak = xasprintf ("%s.disabled", confd);
+
+  write_cache_file (cache, cache_file->data, cache_file->length);
+
+  /* The runtime bypasses the cache when GCONV_PATH is set.  */
+  unsetenv ("GCONV_PATH");
+
+  move_cache_file (conf, conf_bak);
+  move_cache_file (confd, confd_bak);
+
+  /* Force a module resolution, which here can only come from the cache.  */
+  iconv_t cd = iconv_open ("EUC-JP", "UTF-8");
+  TEST_VERIFY (cd != (iconv_t) -1);
+
+  {
+    /* ASCII is a subset of EUC-JP, so 'A' converts to itself.  */
+    char in[] = "A";
+    char out[8];
+    char *inp = in;
+    char *outp = out;
+    size_t inleft = 1;
+    size_t outleft = sizeof (out);
+    TEST_VERIFY (iconv (cd, &inp, &inleft, &outp, &outleft) != (size_t) -1);
+    TEST_COMPARE (outp - out, 1);
+    TEST_COMPARE (out[0], 'A');
+    TEST_COMPARE (iconv_close (cd), 0);
+  }
+
+  /* Restore the configuration for any later use of the container.  */
+  TEST_COMPARE (rename (conf_bak, conf), 0);
+  TEST_COMPARE (rename (confd_bak, confd), 0);
+
+  free (cache);
+  free (conf);
+  free (confd);
+  free (conf_bak);
+  free (confd_bak);
+}
+
+static int
+do_test (void)
+{
+  iconvconfig = xasprintf ("%s/iconvconfig", support_sbindir_prefix);
+  gconvdir = xasprintf ("%s/gconv", support_libdir_prefix);
+
+  char *cache1;
+  xclose (create_temp_file ("iconvconfig-cache1-", &cache1));
+  char *cache2;
+  xclose (create_temp_file ("iconvconfig-cache2-", &cache2));
+
+  run_iconvconfig (cache1);
+  run_iconvconfig (cache2);
+
+  struct cache_file_t cache_file1 = read_cache_file (cache1);
+  struct cache_file_t cache_file2 = read_cache_file (cache2);
+
+  /* Check if the cache generation is deterministic.  */
+  TEST_VERIFY (cache_file1.length > 0);
+  TEST_COMPARE (cache_file1.length, cache_file2.length);
+  TEST_COMPARE_BLOB (cache_file1.data, cache_file1.length,
+		     cache_file1.data, cache_file1.length);
+
+  /* And well-formed.  */
+  check_valid_cache (&cache_file1);
+
+  /* And the runtime must be able to load it and convert through it.  */
+  check_loadable_cache (&cache_file2);
+
+  free_cache_file (&cache_file1);
+  free_cache_file (&cache_file2);
+  free (iconvconfig);
+  free (gconvdir);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/iconv/tst-iconvconfig-cache.root/postclean.req b/iconv/tst-iconvconfig-cache.root/postclean.req
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/iconv/tst-iconvconfig-cache.root/preclean.req b/iconv/tst-iconvconfig-cache.root/preclean.req
new file mode 100644
index 00000000000..e69de29bb2d
-- 
2.43.0