mirror of
https://github.com/scylladb/scylladb.git
synced 2026-06-03 21:47:10 +00:00
a517fcf970
this change is inspired by following warning from clang-tidy
```
Warning: /home/runner/work/scylladb/scylladb/service/storage_proxy.cc:884:13: warning: 'tr_state' used after it was moved [bugprone-use-after-move]
884 | if (tr_state) {
| ^
/home/runner/work/scylladb/scylladb/service/storage_proxy.cc:872:139: note: move occurred here
872 | auto f = get_schema_for_read(proposal.update.schema_version(), src_addr, *timeout).then([&sp = _sp, &sys_ks = _sys_ks, tr_state = std::move(tr_state),
| ^
```
this is not a false positive. as `tr_state` is a captured by move for
constructing a variable in the captured list of a lambda which is in
turn passed to the expression evaluated to `f`.
even the expression itself is not evaluated yet when we reference
`tr_state` to check if it is empty after preparing the expression,
`tr_state` is already moved away into the captured variable. so
at that moment, the statement of `f = f.finally(...)` is never
evaluated, because `tr_state` is always empty by then.
so before this change, the trace message is never recorded.
in this change, we address this issue by capturing `tr_state` by
copying it. as `tr_state` is backed by a `lw_shared_ptr`, the overhead is
neglectable.
after this change, the tracing message is recorded.
the change introduced this issue was 548767f91e.
please note, we could coroutinize this function to improve its
readability, but since this is a fix and should be backported,
let's start with a minimal fix, and worry about the readability
in a follow-up change.
Refs 548767f91e
Fixes #18725
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes scylladb/scylladb#18702