.. _program_listing_file_include_rcutils_visibility_control_macros.h:

Program Listing for File visibility_control_macros.h
====================================================

|exhale_lsh| :ref:`Return to documentation for file <file_include_rcutils_visibility_control_macros.h>` (``include/rcutils/visibility_control_macros.h``)

.. |exhale_lsh| unicode:: U+021B0 .. UPWARDS ARROW WITH TIP LEFTWARDS

.. code-block:: cpp

   // Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   //
   // 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 RCUTILS__VISIBILITY_CONTROL_MACROS_H_
   #define RCUTILS__VISIBILITY_CONTROL_MACROS_H_
   
   // Defines macros to express whether a symbol is localed, imported, or exported
   //
   // Those macros are compatible with GCC, clang, and Microsoft Visual C++. They
   // can be used to enforce which symbols of a library are publicly accessible.
   //
   // RCUTILS_IMPORT, RCUTILS_EXPORT, and RCUTILS_LOCAL are respectively declaring
   // an imported, exported, or local symbol.
   // RCUTILS_LOCAL can be used directly. However, RCUTILS_IMPORT, and
   // RCUTILS_EXPORT may not be used directly. Every project need to provide
   // an additional header called `visibility_macros.h` containing:
   //
   // #ifdef <project>_BUILDING_DLL
   // # define <project>_PUBLIC RCUTILS_EXPORT
   // #else
   // # define <project>_PUBLIC RCUTILS_IMPORT
   // #endif // !<project>_BUILDING_DLL
   // #define <project>_LOCAL RCUTILS_LOCAL
   //
   // ...where "<project>" has been replaced by the project name, such as
   // "MY_PROJECT".
   // Your project CMakeLists.txt should also contain the following statement:
   //
   // target_compile_definitions(<your library> PRIVATE "<project>_BUILDING_DLL")
   //
   // A public (exported) class should then be tagged as <project>_PUBLIC, whereas
   // a non-public class should be tagged with <project>_LOCAL.
   //
   // See GCC documentation: https://gcc.gnu.org/wiki/Visibility
   
   #if defined(_MSC_VER) || defined(__CYGWIN__)
   // Use the Windows syntax when compiling with Microsoft Visual C++.
   //
   // GCC on Windows also support this syntax. When compiling with cygwin,
   // prefer using dllimport/dllexport are the semantic of those flags is closer
   // to msvc++ behavior. See GCC documentation:
   // https://gcc.gnu.org/onlinedocs/gcc/Microsoft-Windows-Function-Attributes.html
   # define RCUTILS_IMPORT __declspec(dllimport)
   # define RCUTILS_EXPORT __declspec(dllexport)
   # define RCUTILS_LOCAL
   #else  // defined(_MSC_VER) || defined(__CYGWIN__)
   // On Linux, use the GCC syntax. This syntax is understood by other compilers
   // such as clang, icpc, and xlc++.
   # define RCUTILS_IMPORT __attribute__ ((visibility("default")))
   # define RCUTILS_EXPORT __attribute__ ((visibility("default")))
   # define RCUTILS_LOCAL  __attribute__ ((visibility("hidden")))
   #endif  // !defined(_MSC_VER) && !defined(__CYGWIN__)
   
   #endif  // RCUTILS__VISIBILITY_CONTROL_MACROS_H_