binlog.binlog_update_returning_into_mixed fails testing UPDATE ... RETURNING ... INTO (MDEV-39563) on MSAN builder

binlog.binlog_update_returning_into_mixed fails in buildbot on release branches 10.11, 11.4 and 11.8, on the UPDATE ... RETURNING ... INTO statement (MDEV-39563).

Build Run Info

Failure text

Identical across all matched occurrences. The buildbot failure cross-reference only captures the query context leading up to the failure, not the actual error/crash message:

#

# MDEV-39563 Implement UPDATE ... RETURNING ... INTO

#

CREATE TABLE t1 (a INT, b VARCHAR(10));

INSERT INTO t1 VALUES (10,'b10');

UPDATE t1 SET a=a+1 RETURNING a INTO @a;

Analysis

All 4 matching occurrences in the window (across 10.11, 11.4 and 11.8) occur on a single builder, amd64-msan-clang-22, pointing at this specific MSAN test/build path rather than a broad per-branch regression. The parent feature ticket MDEV-39563 (status: In Testing) covers UPDATE ... RETURNING ... INTO generally; two other open tickets against that feature (MDEV-41265, MDEV-41260) cover different scenarios (stored-procedure ROW/variable targets), not this plain user-variable (@a) case, so this is not a duplicate. Since no error/crash text was captured, the actual symptom (SQL error, assert, or sanitizer finding) needs to be reproduced directly against an amd64 MSAN build to confirm.

Created via the mtr-failure-bug skill.