Where is RCLCPP_INFO definition and how it works

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Hello there,

I am trying to understand how LOG system works on ROS2. When I try to find the definition of RCLCPP_INFO from galactic source and found nothing but one under build directory as below: ../../../ros2_galactic_src/build/rclcpp/include/rclcpp/logging.hpp

As I know, filese under build are all temp files created or copied from other places. So my question here is where is the origial definition of RCLCPP_INFO( Actually, a series of this kind APIs)？

In addtion, If I am right, the undergound of the log systems is log4cxx library. If so, where is the place to load this library?

Thanks Rongcai Ling