Compilation performance is rather slow

Bug report

I find the compile times for simple ROS logic to be quite high. We have a system with around 100 topics set up with a CI toolchain etc. As build times increased I did some digging around and one of the issue is the compilation performance of ros function calls (eg create_subscription)

Required Info:

• Operating System:
  • Ubuntu 20.04
• Installation type:
  • apt install ros-galactic-dekstop
• Version or commit hash:
  • ros-galactic-desktop/focal,now 0.9.3-2focal.20220430.204723 amd64
• DDS implementation:
  • default
• Client library (if applicable):
  • rclcpp

Steps to reproduce issue

Minimal example that creates some subscriptions:

#include <geometry_msgs/msg/pose_array.hpp>
#include <geometry_msgs/msg/quaternion_stamped.hpp>
#include <geometry_msgs/msg/twist.hpp>
#include <rclcpp/node.hpp>

void test() {
  rclcpp::Node node("test");
  node.create_subscription<geometry_msgs::msg::Twist>("test1", rclcpp::QoS(1), [](geometry_msgs::msg::Twist::ConstSharedPtr) {});
  node.create_subscription<geometry_msgs::msg::PoseArray>("test2", rclcpp::QoS(1), [](geometry_msgs::msg::PoseArray::ConstSharedPtr) {});
  node.create_subscription<geometry_msgs::msg::QuaternionStamped>("test3", rclcpp::QoS(1), [](geometry_msgs::msg::QuaternionStamped::ConstSharedPtr) {});
}

compile:
time /usr/bin/c++ -isystem /opt/ros/galactic/include -Wall -Wextra -std=gnu++17 -c test.cc

Expected behavior

I don't now? Up to 2s max?

Actual behavior

On my system (intel i7@1.9Ghz x8, 16G, SSD, gcc 9.4.0):

• gcc takes about 8 seconds.
• (clang about 4.5 seconds, significantly faster but I can not make the switch at this moment...)

The above example results in an object file that's 11M and contains about 17.000 symbols, so I think all the in-header and template definitions are exploding a bit.

Is there a work around that someone knows of, or is it possible to make a leaner header file?

Start by reproducing the reported case in test.cc with the provided g++ command and compare its timing with clang. Read the rclcpp client-library path exercised by Node::create_subscription and inspect the generated object size and symbols. Done means identifying a supported cause or workaround and measuring a concrete compilation improvement.