Merge bitcoin/bitcoin#32647: build: add -Wthread-safety-pointer

83bfe14 build: add -Wthread-safety-pointer (fanquake)
240a4fb Squashed 'src/leveldb/' changes from 113db4962b..aba469ad6a (fanquake)

Pull request description:

  This will become available in Clang 21:

  > ThreadSafetyAnalysis now supports -Wthread-safety-pointer, which
  > enables warning on passing or returning pointers to guarded variables
  > as function arguments or return value respectively. Note that
  > ThreadSafetyAnalysis still does not perform alias analysis. The
  > feature will be default-enabled with -Wthread-safety in a future release.

  See https://github.com/llvm/llvm-project/blob/main/clang/docs/ReleaseNotes.rst.

  Also updates the leveldb subtree to pull: bitcoin-core/leveldb-subtree#54.

ACKs for top commit:
  davidgumberg:
    Tested ACK  bitcoin/bitcoin@83bfe14
  maflcko:
    lgtm ACK 83bfe14
  theuni:
    utACK 83bfe14

Tree-SHA512: 9bc80bd04a9cebed8aca20bc23a17e52a6a89a1fb042993322f43dbf7bd93de509c091ebb69255063833b098ab11a64285eccf61e17b9f94f974c734a20ad8da

Author: fanquake

CMakeLists.txt

@@ -443,6 +443,7 @@ else()
   try_append_cxx_flags("-Wvla" TARGET warn_interface SKIP_LINK)
   try_append_cxx_flags("-Wshadow-field" TARGET warn_interface SKIP_LINK)
   try_append_cxx_flags("-Wthread-safety" TARGET warn_interface SKIP_LINK)
+  try_append_cxx_flags("-Wthread-safety-pointer" TARGET warn_interface SKIP_LINK)
   try_append_cxx_flags("-Wloop-analysis" TARGET warn_interface SKIP_LINK)
   try_append_cxx_flags("-Wredundant-decls" TARGET warn_interface SKIP_LINK)
   try_append_cxx_flags("-Wunused-member-function" TARGET warn_interface SKIP_LINK)

src/leveldb/util/cache.cc

@@ -171,8 +171,8 @@ class LRUCache {
  private:
   void LRU_Remove(LRUHandle* e);
   void LRU_Append(LRUHandle* list, LRUHandle* e);
-  void Ref(LRUHandle* e);
-  void Unref(LRUHandle* e);
+  void Ref(LRUHandle* e) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  void Unref(LRUHandle* e) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
   bool FinishErase(LRUHandle* e) EXCLUSIVE_LOCKS_REQUIRED(mutex_);
 
   // Initialized before use.