Add minimum test case for verifying exported function registration on…

…ly happens once.

cpp/src/gandiva/CMakeLists.txt

@@ -240,6 +240,7 @@ add_gandiva_test(internals-test
                  tree_expr_test.cc
                  encrypt_utils_test.cc
                  expr_decomposer_test.cc
+                 exported_funcs_registry_test.cc
                  expression_registry_test.cc
                  selection_vector_test.cc
                  lru_cache_test.cc

cpp/src/gandiva/exported_funcs.h

@@ -18,6 +18,7 @@
 #pragma once
 
 #include <vector>
+#include "gandiva/visibility.h"
 
 namespace gandiva {
 
@@ -61,6 +62,5 @@ class ExportedHashFunctions : public ExportedFuncsBase {
   void AddMappings(Engine* engine) const override;
 };
 
-void RegisterExportedFuncs();
-
+GANDIVA_EXPORT void RegisterExportedFuncs();
 }  // namespace gandiva

cpp/src/gandiva/exported_funcs_registry.h

@@ -21,14 +21,15 @@
 #include <vector>
 
 #include <gandiva/engine.h>
+#include <gandiva/visibility.h>
 
 namespace gandiva {
 
 class ExportedFuncsBase;
 
 /// Registry for classes that export functions which can be accessed by
 /// LLVM/IR code.
-class ExportedFuncsRegistry {
+class GANDIVA_EXPORT ExportedFuncsRegistry {
  public:
   using list_type = std::vector<std::shared_ptr<ExportedFuncsBase>>;
 
@@ -42,6 +43,8 @@ class ExportedFuncsRegistry {
 
  private:
   static list_type& registered();
+
+  FRIEND_TEST(ExportedFuncsRegistry, RegistrationOnlyOnce);
 };
 
 #define REGISTER_EXPORTED_FUNCS(classname)               \

cpp/src/gandiva/exported_funcs_registry_test.cc

@@ -0,0 +1,28 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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.
+
+#include "gandiva/exported_funcs_registry.h"
+#include <gtest/gtest.h>
+#include "gandiva/exported_funcs.h"
+
+namespace gandiva {
+TEST(ExportedFuncsRegistry, RegistrationOnlyOnce) {
+  gandiva::RegisterExportedFuncs();
+  auto const& registered_list = ExportedFuncsRegistry::registered();
+  EXPECT_EQ(registered_list.size(), 6);
+}
+}  // namespace gandiva