pub const DEPTH_SYSTEM_DEFAULT: u32 = 0;Expand description
The depth sentinel — “the caller did not state a queue depth”.
issue 0829. Upstream spells it RMW_QOS_POLICY_DEPTH_SYSTEM_DEFAULT = 0
(rmw/include/rmw/types.h); depth is size_t there and uint16_t in our
C ABI, but 0 is 0 in both. The value was already free on every backend:
Cyclone REJECTS KEEP_LAST with depth 0 outright
(validate_history_qospolicy, ddsi_plist.c:2603-2604), the XRCE client
already reads it as “unstated” and drops the field from the wire
(create_entities_bin.c:148), and both read_entity_qos
(nros-rmw-cyclonedds/src/qos.cpp:138) and report_qos_downgrade
(nros-rmw-cffi/src/lib.rs:1903) already treat a 0 read-back as “no
answer” rather than as an answer.