logging_callback in pendulum_log.cpp fails to output to fstream

[y-okumura-isp]

Bug report

I'm working on ros2/realtime_support#94.
We want to change some rttest APIs such as timespec_to_long to timspec_to_uint64.
As these functions are used in pendulum_control, now I'm changing and testing pendulum_control.
In this work, I found the result of timespec_to_long should be printed but actually not.

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • trunk
• Version or commit hash:
  • b17664c (tag: 0.9.3)
• DDS implementation:
  • FastRTPS
• Client library (if applicable):
  • NA

Steps to reproduce issue

./build/pendulum_control/pendulum_logger > stdout.csv &
./build/pendulum_control/pendulum_demo -i 10000

See pendulum_logger_results.csv or stdout or stderr, but I couldn't see output of following line.
https://github.com/ros2/demos/blob/master/pendulum_control/src/pendulum_logger.cpp#L62

The code tries to output to fstream (may be pendulum_logger_result.csv),
but pendulum_logger_result.csv is following, only one line.

iteration timestamp latency minor_pagefaults minor_pagefaults

Expected behavior

We get log in pendulum_logger_results.csv.

Actual behavior

No log in pendulum_logger_results.csv.

Additional information

I think the problem comes from the capture of logging_callback lambda.
The variable fstream is opened outside lambda but not captured.
And fstream is defined in logging_callback lambda without file specification.
According to http://www.cplusplus.com/reference/fstream/ofstream/ofstream/, fstream may be the internal file stream buffer and not associated with file.

  // pendulum_logger.cpp L43-67
  fstream.open(filename, std::ios_base::app);
  size_t i = 0;
  auto logging_callback =
    [&i](const pendulum_msgs::msg::RttestResults::SharedPtr msg) {
      // snip
      std::ofstream fstream;
      // snip
      fstream << i << ...;
  };
  
  auto subscription = logger_node->create_subscription<pendulum_msgs::msg::RttestResults>(
    "pendulum_statistics", qos, logging_callback);

I fixed as bellow,

  auto logging_callback =
    [&i, &fstream](const pendulum_msgs::msg::RttestResults::SharedPtr msg) {
      // std::ofstream fstream;  // delete this lins
      fstream << i << ...;

and get output in pendulum_logger_results.csv.

iteration timestamp latency minor_pagefaults minor_pagefaults
0 16255610679777739 53398 0 0
1 16255610680782905 53605 0 0
2 16255610681776418 54227 0 0
3 16255610682780484 53133 0 0
4 16255610683779059 53202 0 0

If it's OK, I'll send PR.

[clalancette]

Honestly, that looks like debugging code. And since it is hasn't been enabled in a long time, I think I would just delete that whole block (most of the information is printed by the printf above anyway).

[clalancette]

Fixed by #477, so closing.