Add force link macro

* It could help us get rid of --whole-archieve.
* Add comments

paddle/utils/ForceLink.h

@@ -0,0 +1,46 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+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. */
+
+#pragma once
+
+/// Declare a force link file ID. It can be enabled by
+/// `PADDLE_ENABLE_FORCE_LINK_FILE`. It is
+///
+/// Example:
+///
+/// In some_file.cpp
+/// @code{cpp}
+/// static paddle::InitFunction init([]{...});
+/// PADDLE_REGISTER_FORCE_LINK_FILE(some_file)
+/// @endcode{cpp}
+///
+/// In main.cpp
+/// @code{cpp}
+/// PADDLE_ENABLE_FORCE_LINK_FILE(some_file);
+///
+/// int main() {
+///   ...
+/// }
+/// @endcode{cpp}
+///
+/// Then the InitFunction in some_file.cpp can be invoked.
+#define PADDLE_REGISTER_FORCE_LINK_FILE(ID) \
+  int __paddle_register_force_link_file_##ID##_method__() { return 0; }
+
+/// Enable a force link file. The file with ID's static variables could
+/// be all initialized.
+#define PADDLE_ENABLE_FORCE_LINK_FILE(ID)                         \
+  extern int __paddle_register_force_link_file_##ID##_method__(); \
+  static int __paddle_register_force_link_file_##ID##_handler__ = \
+      __paddle_register_force_link_file_##ID##_method__();

paddle/utils/tests/CMakeLists.txt

@@ -15,3 +15,11 @@ if(NOT APPLE)
         COMMAND ${PROJ_ROOT}/paddle/utils/tests/test_CustomStackTracePrint.sh
         WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 endif()
+
+add_library(test_class_registrar_lib STATIC
+  test_ClassRegistrarLib.cpp
+  test_ClassRegistrarGlobals.cpp)
+
+add_simple_unittest(test_ClassRegistrar)
+target_link_libraries(test_ClassRegistrar
+  test_class_registrar_lib)

paddle/utils/tests/test_ClassRegistrar.cpp

@@ -0,0 +1,27 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+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. */
+
+#include <gtest/gtest.h>
+#include <paddle/utils/ForceLink.h>
+#include "test_ClassRegistrarLib.h"
+// Enable link test_ClassRegistrarLib.cpp
+PADDLE_ENABLE_FORCE_LINK_FILE(test_registrar);
+
+TEST(ClassRegistrar, test) {
+  std::vector<std::string> types;
+  gTestRegistrar_.forEachType(
+      [&types](const std::string& tp) { types.push_back(tp); });
+  ASSERT_EQ(1, types.size());
+  ASSERT_EQ("test", types[0]);
+}

paddle/utils/tests/test_ClassRegistrarGlobals.cpp

@@ -0,0 +1,16 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+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. */
+
+#include "test_ClassRegistrarLib.h"
+paddle::ClassRegistrar<BaseClass> gTestRegistrar_;

paddle/utils/tests/test_ClassRegistrarLib.cpp

@@ -0,0 +1,31 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+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. */
+
+#include "test_ClassRegistrarLib.h"
+#include <paddle/utils/ForceLink.h>
+BaseClass::~BaseClass() {}
+
+class TestRegistrar : public BaseClass {
+public:
+  TestRegistrar() {}
+
+  virtual ~TestRegistrar() {}
+};
+
+static paddle::InitFunction init([] {
+  gTestRegistrar_.registerClass(
+      "test", []() -> BaseClass* { return new TestRegistrar(); });
+});
+
+PADDLE_REGISTER_FORCE_LINK_FILE(test_registrar);

paddle/utils/tests/test_ClassRegistrarLib.h

@@ -0,0 +1,23 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+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. */
+
+#pragma once
+#include "paddle/utils/ClassRegistrar.h"
+
+class BaseClass {
+public:
+  virtual ~BaseClass();
+};
+
+extern paddle::ClassRegistrar<BaseClass> gTestRegistrar_;