This leaves as the big gaping holes:
* Cyclone DDS does not allow creating a waitset or a guard condition
outside a participant, and this forces the creation of an additional
participant. It can be fixed in the RMW layer, or it can be dealt
with in Cyclone DDS, but the trouble with the latter is that there are
solid reasons for not allowing it, even if it is easy to support it
today. (E.g., a remote procedure call interface ...)
* Cyclone DDS does not currently support multiple domains
simultaneously, and so this RMW implementation ignores the domain_id
parameter in create_node, instead creating all nodes/participants
(including the special participant mentioned above) in the default
domain, which can be controlled via CYCLONEDDS_URI.
* Deserialization only handles native format (it doesn't do any byte
swapping). This is pure laziness, adding it is trivial.
* Deserialization assumes the input is valid and will do terrible things
if it isn't. Again, pure laziness, it's just adding some bounds
checks and other validation code.
* There are some "oddities" with the way service requests and replies
are serialized and what it uses as a "GUID". (It actually uses an
almost-certainly-unique 64-bit number, the Cyclone DDS instance id,
instead of a real GUID.) I'm pretty sure the format is wildly
different from that in other RMW implementations, and so services
presumably will not function cross-implementation.
* The name mangling seems to be compatibl-ish with the FastRTPS
implementation and in some cases using the ros2 CLI for querying the
system works cross-implementation, but not always. The one in this
implementation is reverse-engineered, so trouble may be lurking
somewhere. As a related point: the "no_demangle" option is currently
ignored ... it causes a compiler warning.
