[doc] Add a note about where lock annotations should go.

Author: amitiuttarwar

doc/developer-notes.md

@@ -785,6 +785,11 @@ Threads and synchronization
   get compile-time warnings about potential race conditions in code. Combine annotations in function declarations with
   run-time asserts in function definitions:
 
+  - In functions that are declared separately from where they are defined, the
+    thread safety annotations should be added exclusively to the function
+    declaration. Annotations on the definition could lead to false positives
+    (lack of compile failure) at call sites between the two.
+
 ```C++
 // txmempool.h
 class CTxMemPool

src/test/txvalidationcache_tests.cpp

@@ -13,7 +13,10 @@
 
 #include <boost/test/unit_test.hpp>
 
-bool CheckInputScripts(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck>* pvChecks) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
+                       const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore,
+                       bool cacheFullScriptStore, PrecomputedTransactionData& txdata,
+                       std::vector<CScriptCheck>* pvChecks) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
 BOOST_AUTO_TEST_SUITE(txvalidationcache_tests)
 

src/validation.cpp

@@ -198,7 +198,11 @@ CBlockIndex* BlockManager::FindForkInGlobalIndex(const CChain& chain, const CBlo
 
 std::unique_ptr<CBlockTreeDB> pblocktree;
 
-bool CheckInputScripts(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck>* pvChecks = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
+                       const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore,
+                       bool cacheFullScriptStore, PrecomputedTransactionData& txdata,
+                       std::vector<CScriptCheck>* pvChecks = nullptr)
+                       EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 static FILE* OpenUndoFile(const FlatFilePos &pos, bool fReadOnly = false);
 static FlatFileSeq BlockFileSeq();
 static FlatFileSeq UndoFileSeq();
@@ -1450,7 +1454,10 @@ void InitScriptExecutionCache() {
  *
  * Non-static (and re-declared) in src/test/txvalidationcache_tests.cpp
  */
-bool CheckInputScripts(const CTransaction& tx, TxValidationState& state, const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck>* pvChecks)
+bool CheckInputScripts(const CTransaction& tx, TxValidationState& state,
+                       const CCoinsViewCache& inputs, unsigned int flags, bool cacheSigStore,
+                       bool cacheFullScriptStore, PrecomputedTransactionData& txdata,
+                       std::vector<CScriptCheck>* pvChecks)
 {
     if (tx.IsCoinBase()) return true;