tests: Add test for sys/ptrtag

tests/sys_ptrtag/Makefile

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+include ../Makefile.tests_common
+
+include $(RIOTBASE)/Makefile.include

tests/sys_ptrtag/main.c

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+/*
+ * Copyright (C) 2020 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     tests
+ * @{
+ *
+ * @file
+ * @brief       Test application for the pointer tagging helpers
+ *
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ *
+ * @}
+ */
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "kernel_defines.h"
+#include "ptrtag.h"
+#include "test_utils/expect.h"
+
+typedef struct PTRTAG {
+    uint8_t a;
+} custom_type_t;
+
+/* To rule out that custom type gets aligned by 4 bytes only by chance, we
+ * allocate two subsequently. At least one would be unaligned, if the
+ * alignment requirement is not increased to at least 4
+ */
+static custom_type_t a;
+static custom_type_t b;
+uint8_t PTRTAG c;
+uint8_t PTRTAG d;
+
+int main(void)
+{
+    puts(
+        "Test Application for sys/ptrtag\n"
+        "=====================================\n"
+    );
+
+    void *ptrs[] = {&a, &b, &c, &d};
+    for (uint8_t tag = 0; tag < 4; tag++) {
+        for (size_t i = 0; i < ARRAY_SIZE(ptrs); i++) {
+            void *ptr = ptrs[i];
+            void *tagged = ptrtag(ptr, tag);
+            expect(ptrtag_ptr(tagged) == ptr);
+            expect(ptrtag_tag(tagged) == tag);
+        }
+    }
+
+    puts("TEST PASSED");
+
+    return 0;
+}

tests/sys_ptrtag/tests/01-run.py

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+#!/usr/bin/env python3
+
+#  Copyright (C) 2020 Otto-von-Guericke-Universität Magdeburg
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+# @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+
+import sys
+from testrunner import run
+
+
+def testfunc(child):
+    child.expect("TEST PASSED")
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))