Fix off-by-one error in dds_strretcode (#270)

Signed-off-by: Erik Boasson <eb@ilities.com>

src/ddsrt/tests/CMakeLists.txt

@@ -24,6 +24,7 @@ list(APPEND sources
   "string.c"
   "log.c"
   "random.c"
+  "retcode.c"
   "strlcpy.c"
   "socket.c"
   "select.c")

src/ddsrt/tests/retcode.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright(c) 2006 to 2018 ADLINK Technology Limited and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Eclipse Distribution License
+ * v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+ */
+#include <string.h>
+
+#include "CUnit/Theory.h"
+#include "dds/ddsrt/retcode.h"
+
+CU_TheoryDataPoints(ddsrt_retcode, unknown) = {
+  CU_DataPoints(dds_return_t,
+                DDS_RETCODE_NOT_ALLOWED_BY_SECURITY-1,
+                -(DDS_RETCODE_NOT_ALLOWED_BY_SECURITY-1),
+                DDS_XRETCODE_BASE,
+                -DDS_XRETCODE_BASE,
+                DDS_RETCODE_NOT_FOUND-1,
+                -(DDS_RETCODE_NOT_FOUND-1),
+                INT32_MAX,
+                -INT32_MAX,
+                INT32_MIN)
+};
+
+CU_Theory((dds_return_t ret), ddsrt_retcode, unknown)
+{
+  CU_ASSERT_STRING_EQUAL(dds_strretcode(ret), "Unknown return code");
+}
+
+CU_TheoryDataPoints(ddsrt_retcode, spotchecks) = {
+  CU_DataPoints(dds_return_t,
+                DDS_RETCODE_OK,
+                -DDS_RETCODE_OK,
+                DDS_RETCODE_NOT_ALLOWED_BY_SECURITY,
+                -DDS_RETCODE_NOT_ALLOWED_BY_SECURITY,
+                DDS_RETCODE_IN_PROGRESS,
+                -DDS_RETCODE_IN_PROGRESS,
+                DDS_RETCODE_NOT_FOUND,
+                -DDS_RETCODE_NOT_FOUND),
+  CU_DataPoints(const char *,
+                "Success",
+                "Success",
+                "Not Allowed By Security",
+                "Not Allowed By Security",
+                "Operation in progress",
+                "Operation in progress",
+                "Not found",
+                "Not found")
+};
+
+CU_Theory((dds_return_t ret, const char *exp), ddsrt_retcode, spotchecks)
+{
+  CU_ASSERT_STRING_EQUAL(dds_strretcode(ret), exp);
+}