tests: Test that we can include all headers with an old MAX_VERSION

In principle we could script this so that each max-version.c is compiled
26 times, once per possible MAX_VERSION, but I haven't implemented
that here: just pinning to the oldest possible version is sufficient to
reproduce #2796.

These aren't included in the installed-tests, since they don't really
do anything at runtime (the important thing is that they compile
without warnings).

Reproduces: #2796
Signed-off-by: Simon McVittie <smcv@collabora.com>

gmodule/tests/max-version.c

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2022 Collabora Ltd.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This 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.
+ *
+ * This 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 this library; if not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef GLIB_VERSION_MAX_ALLOWED
+/* This is the oldest version macro available */
+#define GLIB_VERSION_MIN_REQUIRED GLIB_VERSION_2_26
+#define GLIB_VERSION_MAX_ALLOWED GLIB_VERSION_2_26
+#endif
+
+#include <glib.h>
+
+#include <gmodule.h>
+
+static void
+nothing (void)
+{
+  /* This doesn't really do anything: the real "test" is at compile time.
+   * Just make sure the GModule library gets linked. */
+  g_debug ("GModule supported: %s", g_module_supported () ? "yes" : "no");
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/max-version/tested-at-compile-time", nothing);
+  return g_test_run ();
+}

gmodule/tests/meson.build

@@ -1,4 +1,5 @@
 gmodule_tests = {
+  'max-version' : {'install': false},
   'module-test-library' : {
     'export_dynamic' : true,
     'source': 'module-test.c',