fix(jdbc): read updateCount under the statement lock

libsql-jdbc/src/main/java/com/github/magnusp/libsql/jdbc/LibsqlPreparedStatement.java

@@ -57,7 +57,7 @@
         this.sql = sql;
         this.returnsResultSet = returnsResultSet(sql);
         this.parameterCount = SqlTokenizer.placeholderCount(sql);
         this.parameterMetaData = new ParameterMetaDataView(this, parameterCount);
     }
 
     private void setParam(int parameterIndex, Value value) throws SQLException {
@@ -100,7 +100,7 @@
             throw new SQLException("Query returns results");
         }
         execute();
-        return (int) updateCount;
+        return snapshotUpdateCount();
     }
 
     private static boolean returnsResultSet(String sql) {

libsql-jdbc/src/main/java/com/github/magnusp/libsql/jdbc/LibsqlStatement.java

@@ -135,7 +135,18 @@ protected void assignResultSet(
     @Override
     public int executeUpdate(String sql) throws SQLException {
         execute(sql);
-        return (int) updateCount;
+        return snapshotUpdateCount();
+    }
+
+    /**
+     * Reads the update count under {@link #stateLock}, the lock every write to the field holds.
+     * The execute paths that return a count use this instead of reading the field directly, so the
+     * value they hand back has the same happens-before edge as {@link #getUpdateCount()}.
+     */
+    protected int snapshotUpdateCount() {
+        synchronized (stateLock) {
+            return (int) updateCount;
+        }
     }
 
     @Override