Fix memory leak in Parser from unowned root_field allocation

[Copilot]

BuildMessageSchema allocated a ROSField with new but never freed it. Each Parser construction leaked ~50 bytes. Repeatedly creating Parsers in a loop caused unbounded memory growth (9MB → 29MB over 50k iterations in the reported case).

Changes

• Added std::unique_ptr<ROSField> root_field to MessageSchema to own the root field
• Changed BuildMessageSchema to use std::make_unique instead of raw new

The field tree already stored a raw pointer to this field; now the schema owns the allocation and ensures cleanup.

// Before (leaked)
auto root_field = new ROSField(schema->root_msg->type(), topic_name);
schema->field_tree.root()->setValue(root_field);

// After (owned)
schema->root_field = std::make_unique<ROSField>(schema->root_msg->type(), topic_name);
schema->field_tree.root()->setValue(schema->root_field.get());

Original prompt

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This section details on the original issue you should resolve

<issue_title>Possible Memory Leak in Parser object</issue_title>
<issue_description>Ubuntu 24.04.1 LTS
Version: 1.0.2-1noble.20250814.084246

Memory accumulates when creating Parser objects in a loop, even though the Parser goes out of scope at end of loop.

#include <fstream>
#include <iostream>
#include <string>
#include <memory>
#include <chrono>
#include <thread>
#include <rclcpp/serialized_message.hpp>
#include <rosx_introspection/ros_parser.hpp>
#include <rosx_introspection/ros_utils/ros2_helpers.hpp>

void print_memory_usage() {
  std::ifstream statm("/proc/self/statm");
  long size, resident;
  statm >> size >> resident;
  long page_size_kb = sysconf(_SC_PAGESIZE) / 1024;
  std::cout << "Virtual Memory: " << size * page_size_kb << " KB\n";
  std::cout << "Resident Memory: " << resident * page_size_kb << " KB\n";
}

int main() {
    using namespace RosMsgParser;

    const std::string topic = "dummy_topic";
    const std::string type = "std_msgs/String";
    size_t counter = 0;
    std::vector<uint8_t> buffer(1024, 0);
    // No leak
    // Parser parser(topic, ROSType(type), GetMessageDefinition(type));
    while (true) {
      std::string out;
      ROS2_Deserializer deserializer;
      {
        // leak
        Parser parser(topic, ROSType(type), GetMessageDefinition(type));
        Span<const uint8_t> span(buffer.data(), buffer.size());
        parser.deserializeIntoJson(span, &out, &deserializer, 0, true);
      }
      counter++;
      if (counter % 10000 == 0) {
        print_memory_usage();
      }
    }
    return 0;
}

Parser creation inside loop:

Virtual Memory: 12212 KB
Resident Memory: 9088 KB
Virtual Memory: 17236 KB
Resident Memory: 14080 KB
Virtual Memory: 22260 KB
Resident Memory: 19072 KB
Virtual Memory: 27352 KB
Resident Memory: 24192 KB
Virtual Memory: 32376 KB
Resident Memory: 29056 KB

Parser creation outside loop:

Virtual Memory: 7168 KB
Resident Memory: 4096 KB
Virtual Memory: 7264 KB
Resident Memory: 4096 KB
Virtual Memory: 7264 KB
Resident Memory: 4096 KB
Virtual Memory: 7264 KB
Resident Memory: 4096 KB
Virtual Memory: 7264 KB
Resident Memory: 4096 KB

From what I can decipher from valgrind the issue might be in BuildMessageSchema. I noticed very high memory usage in my generic bridge after it had been running in simulation for a day.</issue_description>

Comments on the Issue (you are @copilot in this section)

@facontidavide Thanks a lot, I will investigate

• Fixes Possible Memory Leak in Parser object #24

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