CONCPP-167 Changing of auto_increment_increment with crashed the driver

This could happen only if rewriteBatchedStatements on - only in this
case auto_increment_increment was tracked. If that actually happened, the bug in
the session tracking processing caused unhandled exception that aborted the program.

The test has been added.

Author: lawrinn

src/protocol/capi/QueryProtocol.cpp

@@ -1532,6 +1532,8 @@ namespace capi
         case StateChange::SESSION_TRACK_SYSTEM_VARIABLES:
           if (str.compare("auto_increment_increment") == 0)
           {
+            mysql_session_track_get_next(connection, static_cast<enum capi::enum_session_state_type>(type), &value, &len);
+            str.assign(value, len);
             autoIncrementIncrement= std::stoi(str);
             results->setAutoIncrement(autoIncrementIncrement);
           }

test/unit/classes/connection.cpp

@@ -3553,6 +3553,29 @@ void connection::concpp163()
 }
 
 
+/* CONCPP-167 Changing of the session's auto_increment_increment causes unhandled exception */
+void connection::concpp167()
+{
+  sql::ConnectOptionsMap opts;
+
+  /* The connector asks the server to track the changes of the auto_increment_increment system
+     variable if the rewriteBatchedStatements option is on. Thus testing both kinds of connections */
+  for (auto rewriteBatchedStatements : {"false", "true"}) {
+    opts["rewriteBatchedStatements"]= rewriteBatchedStatements;
+
+    Connection c(getConnection(&opts));
+    Statement s(c->createStatement());
+
+    s->execute("SET SESSION auto_increment_increment=3");
+
+    /* The connection has to be usable, and the new value in effect */
+    ResultSet r(s->executeQuery("SELECT @@session.auto_increment_increment"));
+    ASSERT(r->next());
+    ASSERT_EQUALS(3, r->getInt(1));
+  }
+}
+
+
 void connection::setUp()
 {
   super::setUp();

test/unit/classes/connectiontest.h

@@ -95,6 +95,7 @@ class connection : public unit_fixture
     TEST_CASE(concpp105_conn_concurrency);
     TEST_CASE(concpp112_connection_attributes);
     TEST_CASE(concpp163);
+    TEST_CASE(concpp167);
   }
 
   /**
@@ -293,6 +294,9 @@ class connection : public unit_fixture
   /* allowMultiQueries option, and other client capabilities controlled by connection options */
   void concpp163();
 
+  /* Changing of the session's auto_increment_increment */
+  void concpp167();
+
   void setUp();
 };