Merge #21202: [validation] Two small clang lock annotation improvements

25c57d640992255ed67964a44b17afbfd4bed0cf [doc] Add a note about where lock annotations should go. (Amiti Uttarwar)
ad5f01b96045f304b6cf9100879592b835c49c40 [validation] Move the lock annotation from function definition to declaration (Amiti Uttarwar)

Pull request description:

  Based on reviewing #21188

  the first commit switches the lock annotations on `CheckInputScripts` to be on the function declaration instead of on the function definition. this ensures that all call sites are checked, not just ones that come after the definition.

  the second commit adds a note to the developer-notes section to clarify where the annotations should be applied.

ACKs for top commit:
  MarcoFalke:
    ACK 25c57d640992255ed67964a44b17afbfd4bed0cf 🥘
  promag:
    Code review ACK 25c57d640992255ed67964a44b17afbfd4bed0cf.

Tree-SHA512: 61b6ef856bf6c6016d535fbdd19daf57b9e59fe54a1f30d47282a071b9b9d60b2466b044ee57929e0320cb1bdef52e7a1687cacaa27031bbc43d058ffffe22ba

3 files changed, 18 insertions, 3 deletions

diff --git a/doc/developer-notes.md b/doc/developer-notes.md
index 011c38321c..8f2d7af089 100644
--- a/doc/developer-notes.md
+++ b/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
diff --git a/src/test/txvalidationcache_tests.cpp b/src/test/txvalidationcache_tests.cpp
index 288f807abd..3244b58082 100644
--- a/src/test/txvalidationcache_tests.cpp
+++ b/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);
+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)
 
diff --git a/src/validation.cpp b/src/validation.cpp
index 1b8fb1fd45..0b2ca4b422 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -199,7 +199,11 @@ 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);
+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();
@@ -1481,7 +1485,10 @@ 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) 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)
 {
     if (tx.IsCoinBase()) return true;