Per v4.4 plan: 'no shipped driver daemon opts in yet'. Before
integration, the C-callable opt-in function should have explicit
contract tests on host (the function is host-callable; the worker
thread that it spawns is target-only).
Three new unit tests in rust_impl/error.rs:
- register_returns_false_without_env_var: confirms
pci_register_error_handler returns false when
REDBEAR_DRIVER_ERROR_FD is unset (the daemon was not passed a
sidecar fd by its parent). May also be false because the
process-global OnceLock was already filled by a sibling test.
- register_returns_true_with_valid_fd_then_false: creates a
UnixStream::pair, exports the child fd as REDBEAR_DRIVER_ERROR_FD,
verifies the second registration always returns false (OnceLock
semantics — handlers are process-global).
- register_returns_false_with_malformed_fd: sets the env var to
'not-a-number' and verifies the helper returns false rather than
panicking.
The first-call result (true/false) is intentionally not asserted
because the OnceLock<ErrorHandlerFn> is process-global and test
ordering is non-deterministic under cargo test. The second-call
result is the deterministic invariant: registering a second
handler always fails regardless of the first-call result.
Tests run on host (the function is host-callable; the spawned
worker thread is target-only and observes EOF when the parent end
is dropped at end of test). Target build also clean.
No production code changed.
vasilito
1aa26ba251