Support different types in the parameter store

The test framework stores size_t and int32_t values in the parameter store
by converting them all to int. This is ok in practice, since we assume int
covers int32_t and we don't have test data larger than 2GB. But it's
confusing and error-prone. So make the parameter store a union, which allows
size_t values not to be potentially truncated and makes the code a little
clearer.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

tests/include/test/arguments.h

@@ -0,0 +1,43 @@
+/**
+ * \file arguments.h
+ *
+ * \brief Manipulation of test arguments.
+ *
+ * Much of the code is in host_test.function, to be migrated here later.
+ */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#ifndef TEST_ARGUMENTS_H
+#define TEST_ARGUMENTS_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef union {
+    size_t len;
+    int32_t s32;
+} mbedtls_test_argument_t;
+
+#endif /* TEST_ARGUMENTS_H */