There no compatibility issues with, except for one small change in the creation of "topic" entities. The "create topic" and "find topic" operations now create a new entity (thus with a unique handle), matching the DDS specification. Previously these would simply return the existing one when the topic was already known. This only substantially affects programs that:
- call these operations in a loop for a single topic (this will now leak memory);
- deliberately delete a topic after calling these operations multiple times for that topic with the aim of recreating it with a different QoS (because the topic now remains in existence, this now results in a subsequent dds_create_topic failing with an incompatible QoS error);
- call these operations multiple times for a single topic and compare topic handles of readers/writers (because the handles are now no longer guaranteed to be the same).
Simply calling these functions a few times at start-up without depending on the topic handle being the same will simply mean a slight increase in memory usage. Once one deletes the participant, all these topics will be deleted and no memory will be leaked.
The three cases above are deemed sufficiently rare that the change in behaviour is warranted within a single major version. Indeed, one could even argue this is merely a bug fix.