`LockAnnotation lock(::cs_main)` is a guarantee to the compiler thread analysis that `::cs_main` is locked (when it couldn't be determined otherwise).

Despite being annotated with the locking guarantee ...

https://github.com/bitcoin/bitcoin/blob/65526fc8666fef35ef908dbc225f706bef642c7e/src/interfaces/chain.cpp#L134-L138

... `getTipLocator()` reads `chainActive` (via `::ChainActive()`) without holding `cs_main`.

This can be verified by adding the following `AssertLockHeld(cs_main)`:

```
$ git diff
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index 59623284d..9fc693a0f 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -134,6 +134,7 @@ class LockImpl : public Chain::Lock
     CBlockLocator getTipLocator() override
     {
         LockAnnotation lock(::cs_main);
+        AssertLockHeld(::cs_main);
         return ::ChainActive().GetLocator();
     }
     Optional<int> findLocatorFork(const CBlockLocator& locator) override
$ make check
../build-aux/test-driver: line 107: 12881 Aborted                 "$@" > $log_file 2>&1
FAIL: qt/test/test_bitcoin-qt
```
{
    {
        LOCK(cs_wallet);
        
        std::string strAddress = EncodeDestination(address);
        for (const std::pair<const std::string, std::string> &item : mapAddressBook[address].destdata)
        {
            WalletBatch(*database).EraseDestData(strAddress, item.first);
        }
        mapAddressBook.erase(address);
    }
    NotifyAddressBookChanged(this, address, "", ::IsMine(*this, address) != ISMINE_NO, "", CT_DELETED);
    WalletBatch(*database).ErasePurpose(EncodeDestination(address));
    return WalletBatch(*database).EraseName(EncodeDestination(address));
}
const std::string& CWallet::GetLabelName(const CScript& scriptPubKey) const