Merge bitcoin/bitcoin#34470: Bump leveldb subtree and remove UB workaround in CI

fad7d86d8d ci: Remove unused workaround after leveldb subtree bump (MarcoFalke)
2f2952c5f2 Squashed 'src/leveldb/' changes from cad64b151d..ab6c84e6f3 (MarcoFalke)

Pull request description:

  Bump leveldb subtree and remove UB workaround in CI. This also fixes a GCC-16 warning.

ACKs for top commit:
  l0rinc:
    code review ACK fad7d86d8d
  fanquake:
    ACK fad7d86d8d

Tree-SHA512: dccd53ca638f1acbd72187032d858453e1cc58b156a52e24356c075ac85be0db47d7b73965131b5fbc7b188cbc34cbfd72a8286e860c3b28258daaf5437546f2

ci/test/03_test_script.sh

@@ -44,32 +44,6 @@ echo "=== BEGIN env ==="
 env
 echo "=== END env ==="
 
-# Don't apply patches in the iwyu job, because it relies on the `git diff`
-# command to detect IWYU errors. It is safe to skip this patch in the iwyu job
-# because it doesn't run a UB detector.
-if [[ "${RUN_IWYU}" != true ]]; then
-  # compact->outputs[i].file_size is uninitialized memory, so reading it is UB.
-  # The statistic bytes_written is only used for logging, which is disabled in
-  # CI, so as a temporary minimal fix to work around UB and CI failures, leave
-  # bytes_written unmodified.
-  # See https://github.com/bitcoin/bitcoin/pull/28359#issuecomment-1698694748
-  # Tee patch to stdout to make it clear CI is testing modified code.
-  tee >(patch -p1) <<'EOF'
---- a/src/leveldb/db/db_impl.cc
-+++ b/src/leveldb/db/db_impl.cc
-@@ -1028,9 +1028,6 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
-       stats.bytes_read += compact->compaction->input(which, i)->file_size;
-     }
-   }
--  for (size_t i = 0; i < compact->outputs.size(); i++) {
--    stats.bytes_written += compact->outputs[i].file_size;
--  }
-
-   mutex_.Lock();
-   stats_[compact->compaction->level() + 1].Add(stats);
-EOF
-fi
-
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
   export DIR_FUZZ_IN=${DIR_QA_ASSETS}/fuzz_corpora/
   if [ ! -d "$DIR_FUZZ_IN" ]; then

src/leveldb/db/db_impl.cc

@@ -803,6 +803,7 @@ Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
     pending_outputs_.insert(file_number);
     CompactionState::Output out;
     out.number = file_number;
+    out.file_size = 0;
     out.smallest.Clear();
     out.largest.Clear();
     compact->outputs.push_back(out);