image_transport::CameraPublisher::getNumSubscribers

[mhubii]

image_transport::CameraPublisher::getNumSubscribers does not return the correct number of subscribers in foxy distributed binaries. Building this repo's foxy branch from source mitigates this issue. Minimal example:

#include <rclcpp/rclcpp.hpp>
#include <image_transport/image_transport.hpp>

void cb(const sensor_msgs::msg::Image::ConstSharedPtr) { return; }

int main(int argc, char** argv) {
    rclcpp::init(argc, argv);
    auto node = std::make_shared<rclcpp::Node>("tmp_node");

    std::string topic = "image";
    auto pub = image_transport::create_camera_publisher(node->shared_from_this().get(), topic);
    auto sub = image_transport::create_subscription(node->shared_from_this().get(), topic, cb, "raw");

    while (rclcpp::ok()) {
        RCLCPP_INFO(node->get_logger(), "N subscriptions: %d", pub.getNumSubscribers());
        rclcpp::spin_some(node);
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
    rclcpp::shutdown();
}

ie this will print N subscriptions: 0.

Full example: https://github.com/mhubii/image_transport_bug

[mhubii]

downstream issues are for example ros-perception/image_pipeline#739

[gbiggs]

So this bug is fixed in source but not in the released binaries? Having a new binary release would solve your problem?

[mhubii]

I suppose. But I also haven't checked in a while whether this is still a bug

[gbiggs]

I'll close this issue, then. If you encounter the bug again, please comment here and I'll reopen it and we can try to fix the problem.

[mhubii]

I don't think closing without checking makes sense, especially since there is repository with detailed and quick instructions on how to test https://github.com/mhubii/image_transport_bug

[gbiggs]

OK, I'll re-open it. But this is reported as working in source, and I'm doing a new binary release right now to get that version into the repositories. Please feel free to test and report once the next foxy sync happens if the bug is still present in the new binaries

[mhubii]

hey @gbiggs , I checked and the error seems gone!