ros2GH-14 Add documentation about building the ros1 plugin on Mac

README.md

@@ -27,7 +27,7 @@ $ colcon build --merge-install
 
 The `--merge-install` flag is optional but ensures a cleaner environment which is helpful for development.
 
-#### Executing tests
+### Executing tests
 
 The tests can be run using the following commands:
 
@@ -43,8 +43,9 @@ The first command executes the test and the second command displays the errors (
 It is possible to read old bagfiles with `ros2`.
 This requires translating ROS 1 messages into ROS 2 messages similar to the `ros1_bridge`.
 If your rosbags contain custom message formats which can be translated into ROS 2 messages, the plugins need to be built from source.
+In any case, the plugin needs to have ROS 1 installed on the system, so it is currently unavailable on Windows.
 
-#### Building the plugins
+### Building the plugins
 
 You need to have the `ros1_bridge` built (see <https://index.ros.org/p/ros1_bridge/github-ros2-ros1_bridge/#bouncy>).
 
@@ -58,7 +59,7 @@ This will automatically match all ROS 1 messages to their ROS 2 counterpart usin
 
 **N.B:** The ROS 1 installation must be sourced first to avoid problems with the `class_loader`.
 
-#### Using the plugins
+### Using the plugins
 
 In order to use the plugins, again, the ROS 1 installation must be sourced **before** sourcing the ROS 2 installation.
 
@@ -77,3 +78,27 @@ ros2 bag play -s rosbag_v2 <path_to_bagfile>
 ```
 
 Currently, split bagfiles are unsupported.
+
+### Building the plugin on macOS
+
+Since building the plugin requires ROS 1, which is only officially supported on Debian/Ubuntu, this plugin is also only officially supported on Linux.
+However, if one has a working ROS1 installation on macOS, following the instructions above it should be possible to build and use the plugin on macOS as well.
+
+##### Troubleshooting
+When building the ROS1 plugin on macOS the following error may occur:
+```
+In file included from <path_to_ros>/install_isolated/include/roslz4/lz4s.h:38:
+
+<path_to_lz4>/lz4.h:437:12: error: an attribute list cannot appear here
+LZ4LIB_API LZ4_DEPRECATED("use LZ4_compress_default() instead") int LZ4_compress               (const char* source, char* dest, int sourceSize);
+           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+/opt/local/include/lz4.h:423:37: note: expanded from macro 'LZ4_DEPRECATED'
+#    define LZ4_DEPRECATED(message) [[deprecated(message)]]
+                                    ^~~~~~~~~~~~~~~~~~~~~~~
+```
+This can be fixed by defining `LZ4_DISABLE_DEPRECATE_WARNINGS` before including `lz4` in `roslz4/lz4s.h`:
+```
+#define LZ4_DISABLE_DEPRECATE_WARNINGS
+
+#include <lz4.h>
+```