MDEV-26541 Make UBSAN builds work with spider again.

When built with ubsan and trying to load the spider plugin, the hidden
visibility of mysqld compiling flag causes ha_spider.so to be missing
the symbol ha_partition. This commit fixes that, as well as some
memcpy null pointer issues when built with ubsan.
Signed-off-by: Yuchen Pei <yuchen.pei@mariadb.com>

sql/CMakeLists.txt

@@ -197,6 +197,15 @@ FOREACH(se aria partition perfschema sql_sequence wsrep)
   ENDIF()
 ENDFOREACH()
 
+IF(VISIBILITY_HIDDEN_FLAG AND TARGET partition AND WITH_UBSAN)
+  # the spider plugin needs some partition symbols from inside mysqld
+  # when built with ubsan, in which case we need to remove
+  # -fvisibility=hidden from partition
+  GET_TARGET_PROPERTY(f partition COMPILE_FLAGS)
+  STRING(REPLACE "${VISIBILITY_HIDDEN_FLAG}" "" f ${f})
+  SET_TARGET_PROPERTIES(partition PROPERTIES COMPILE_FLAGS "${f}")
+ENDIF()
+
 IF(WIN32)
   SET(MYSQLD_SOURCE main.cc nt_servc.cc message.rc)
   TARGET_LINK_LIBRARIES(sql psapi)

storage/spider/mysql-test/spider/bugfix/r/mdev_26541.result

+#
+# MDEV-26541 Undefined symbol: _ZTI12ha_partition when attempting to use ha_spider.so in UBSAN builds
+#
+INSTALL PLUGIN spider SONAME 'ha_spider.so';
+DROP FUNCTION spider_flush_table_mon_cache;
+DROP FUNCTION spider_copy_tables;
+DROP FUNCTION spider_ping_table;
+DROP FUNCTION spider_bg_direct_sql;
+DROP FUNCTION spider_direct_sql;
+UNINSTALL PLUGIN spider_alloc_mem;
+UNINSTALL PLUGIN spider;
+DROP TABLE IF EXISTS mysql.spider_xa;
+DROP TABLE IF EXISTS mysql.spider_xa_member;
+DROP TABLE IF EXISTS mysql.spider_xa_failed_log;
+DROP TABLE IF EXISTS mysql.spider_tables;
+DROP TABLE IF EXISTS mysql.spider_link_mon_servers;
+DROP TABLE IF EXISTS mysql.spider_link_failed_log;
+DROP TABLE IF EXISTS mysql.spider_table_position_for_recovery;
+DROP TABLE IF EXISTS mysql.spider_table_sts;
+DROP TABLE IF EXISTS mysql.spider_table_crd;

storage/spider/mysql-test/spider/bugfix/t/mdev_26541.test

+--echo #
+--echo # MDEV-26541 Undefined symbol: _ZTI12ha_partition when attempting to use ha_spider.so in UBSAN builds
+--echo #
+
+if (`select not(count(*)) from information_schema.system_variables where variable_name='have_sanitizer' and global_value="UBSAN"`)
+{
+--skip test needs to be run with UBSAN
+}
+
+# init spider
+
+INSTALL PLUGIN spider SONAME 'ha_spider.so';
+
+let $PLUGIN_NAME= spider_flush_table_mon_cache;
+let $PLUGIN_EXIST=
+  `SELECT COUNT(*) FROM mysql.func WHERE name = '$PLUGIN_NAME'`;
+while (!$PLUGIN_EXIST)
+{
+  let $PLUGIN_EXIST=
+    `SELECT COUNT(*) FROM mysql.func WHERE name = '$PLUGIN_NAME'`;
+}
+
+# deinit spider
+
+DROP FUNCTION spider_flush_table_mon_cache;
+DROP FUNCTION spider_copy_tables;
+DROP FUNCTION spider_ping_table;
+DROP FUNCTION spider_bg_direct_sql;
+DROP FUNCTION spider_direct_sql;
+UNINSTALL PLUGIN spider_alloc_mem;
+UNINSTALL PLUGIN spider;
+DROP TABLE IF EXISTS mysql.spider_xa;
+DROP TABLE IF EXISTS mysql.spider_xa_member;
+DROP TABLE IF EXISTS mysql.spider_xa_failed_log;
+DROP TABLE IF EXISTS mysql.spider_tables;
+DROP TABLE IF EXISTS mysql.spider_link_mon_servers;
+DROP TABLE IF EXISTS mysql.spider_link_failed_log;
+DROP TABLE IF EXISTS mysql.spider_table_position_for_recovery;
+DROP TABLE IF EXISTS mysql.spider_table_sts;
+DROP TABLE IF EXISTS mysql.spider_table_crd;

storage/spider/spd_conn.cc

@@ -518,18 +518,25 @@ SPIDER_CONN *spider_create_conn(
     conn->tgt_host = tmp_host;
     memcpy(conn->tgt_host, share->tgt_hosts[link_idx],
       share->tgt_hosts_lengths[link_idx]);
+
     conn->tgt_username_length = share->tgt_usernames_lengths[link_idx];
     conn->tgt_username = tmp_username;
-    memcpy(conn->tgt_username, share->tgt_usernames[link_idx],
-      share->tgt_usernames_lengths[link_idx]);
+    if (conn->tgt_username_length)
+      memcpy(conn->tgt_username, share->tgt_usernames[link_idx],
+             share->tgt_usernames_lengths[link_idx]);
+
     conn->tgt_password_length = share->tgt_passwords_lengths[link_idx];
     conn->tgt_password = tmp_password;
-    memcpy(conn->tgt_password, share->tgt_passwords[link_idx],
-      share->tgt_passwords_lengths[link_idx]);
+    if (conn->tgt_password_length)
+      memcpy(conn->tgt_password, share->tgt_passwords[link_idx],
+             share->tgt_passwords_lengths[link_idx]);
+
     conn->tgt_socket_length = share->tgt_sockets_lengths[link_idx];
     conn->tgt_socket = tmp_socket;
-    memcpy(conn->tgt_socket, share->tgt_sockets[link_idx],
-      share->tgt_sockets_lengths[link_idx]);
+    if (conn->tgt_socket_length)
+      memcpy(conn->tgt_socket, share->tgt_sockets[link_idx],
+             share->tgt_sockets_lengths[link_idx]);
+
     conn->tgt_wrapper_length = share->tgt_wrappers_lengths[link_idx];
     conn->tgt_wrapper = tmp_wrapper;
     memcpy(conn->tgt_wrapper, share->tgt_wrappers[link_idx],