Possible memory leak (after dis-, then reconnect of Agent)

[gavanderhoorn]

As mentioned in the Known issues & limitations section of the README (here), MotoROS2 currently appears to suffer from a small memory leak.

Testing shows the following values for used and free memory after several consecutive connect and disconnect cycles with a Galactic micro-ROS Agent:

Initialization complete. Memory available: (962992) bytes. Memory in use: (85584) bytes
Initialization complete. Memory available: (962992) bytes. Memory in use: (85584) bytes
Initialization complete. Memory available: (962552) bytes. Memory in use: (86024) bytes
Initialization complete. Memory available: (962280) bytes. Memory in use: (86296) bytes
Initialization complete. Memory available: (962280) bytes. Memory in use: (86296) bytes
Initialization complete. Memory available: (962280) bytes. Memory in use: (86296) bytes
Initialization complete. Memory available: (962256) bytes. Memory in use: (86320) bytes
Initialization complete. Memory available: (962224) bytes. Memory in use: (86352) bytes

As a table:

#	Free	Delta	In use	Delta
0	962992		85584
1	962992	0	85584	0
2	962552	-440	86024	440
3	962280	-272	86296	272
4	962280	0	86296	0
5	962280	0	86296	0
6	962256	-24	86320	24
7	962224	-32	86352	32

No changes to the config file between reboots dis-and-re-connects.

It's unclear what causes this at this point.

[gavanderhoorn]

Summary of earlier findings/comments:

• we could be handling message/service/action memory incorrectly. The micro-ROS documentation specifically states:

  If the init function is called twice for the same message without calling fini in between previously allocated memory will be leaked

  There's *_create()/*_destroy() and micro_ros_utilities_create_message_memory(..)/micro_ros_utilities_destroy_message_memory(..) in micro_ros_utils. Calling *_create() and then *_init() on sequence fields might also leak memory.

• our libmicroros might be missing some fixes upstream already has: we're using https://github.com/micro-ROS/rmw_microxrcedds/commit/a2a74846971697e4afc8a70b59c9a8352d74195b in our Humble builds, but according to the commit history, a couple commits later https://github.com/micro-ROS/rmw_microxrcedds/pull/280 gets merged (as https://github.com/micro-ROS/rmw_microxrcedds/commit/6df0003fe6d36fbcab77b5a663acba738e265890). From the description, it sounds like this could have something to do with the memory leak we're seeing.