Merge bitcoin/bitcoin#28359: ci: Asan with -ftrivial-auto-var-init=pattern

fa07ac48d8 ci: Asan with -ftrivial-auto-var-init=pattern (MarcoFalke)

Pull request description:

  This makes memory bugs deterministic. `-ftrivial-auto-var-init=pattern` is incompatible with other memory sanitizers (like valgrind and msan), but that is irrelevant here, because the address sanitizer in this fuzz CI config is already incompatible with them.

  `-ftrivial-auto-var-init=pattern` goes well with `-fsanitize=bool` and `-fsanitize=enum`, but those are already enabled via `-fsanitize=undefined`. See https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#available-checks

ACKs for top commit:
  fanquake:
    ACK fa07ac48d8 - going to get back to fixing up the cxxflags usage in CI, but not a blocker here:

Tree-SHA512: 2ea6c5128a9cd262bdd1b1475c7e1be23ce2c520fad05f6c2aace6c29e203573323c0564d272e25da35ad5ff46fde488a5eae1ed14d3349e793d14a5e2533fb1

ci/test/00_setup_env_native_asan.sh

@@ -22,4 +22,5 @@ export NO_DEPENDS=1
 export GOAL="install"
 export BITCOIN_CONFIG="--enable-c++20 --enable-usdt --enable-zmq --with-incompatible-bdb --with-gui=qt5 \
 CPPFLAGS='-DARENA_DEBUG -DDEBUG_LOCKORDER' \
---with-sanitizers=address,float-divide-by-zero,integer,undefined CC=clang-16 CXX=clang++-16"
+--with-sanitizers=address,float-divide-by-zero,integer,undefined \
+CC='clang-16 -ftrivial-auto-var-init=pattern' CXX='clang++-16 -ftrivial-auto-var-init=pattern'"

ci/test/06_script_b.sh

@@ -29,6 +29,29 @@ df -h
 # Tests that run natively guess the host
 export HOST=${HOST:-$("$BASE_ROOT_DIR/depends/config.guess")}
 
+(
+  # 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
+  echo 'diff --git a/src/leveldb/db/db_impl.cc b/src/leveldb/db/db_impl.cc
+index 65e31724bc..f61b471953 100644
+--- 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);' | patch -p1
+  git diff
+)
+
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
   export DIR_FUZZ_IN=${DIR_QA_ASSETS}/fuzz_seed_corpus/
   if [ ! -d "$DIR_FUZZ_IN" ]; then