cleanup: use null_lex_str where appropriate

sql/sp_head.cc

@@ -582,8 +582,6 @@ sp_head::sp_head()
    m_next_cached_sp(0),
    m_cont_level(0)
 {
-  const LEX_STRING str_reset= { NULL, 0 };
-
   m_first_instance= this;
   m_first_free_instance= this;
   m_last_cached_sp= this;
@@ -594,7 +592,7 @@ sp_head::sp_head()
     be rewritten soon. Remove the else part and replace 'if' with
     an assert when this is done.
   */
-  m_db= m_name= m_qname= str_reset;
+  m_db= m_name= m_qname= null_lex_str;
 
   DBUG_ENTER("sp_head::sp_head");
 

sql/sql_lex.cc

@@ -515,8 +515,7 @@ void lex_start(THD *thd)
   lex->check_exists= FALSE;
   lex->verbose= 0;
 
-  lex->name.str= 0;
+  lex->name= null_lex_str;
-  lex->name.length= 0;
   lex->event_parse_data= NULL;
   lex->profile_options= PROFILE_NONE;
   lex->nest_level=0 ;

sql/sql_lex.h

@@ -135,6 +135,9 @@ struct sys_var_with_base
 
 #ifdef MYSQL_SERVER
 
+extern const LEX_STRING null_lex_str;
+extern const LEX_STRING empty_lex_str;
+
 enum enum_sp_suid_behaviour
 {
   SP_IS_DEFAULT_SUID= 0,
@@ -242,8 +245,7 @@ struct LEX_MASTER_INFO
     heartbeat_period= 0;
     ssl= ssl_verify_server_cert= heartbeat_opt=
       repl_ignore_server_ids_opt= LEX_MI_UNCHANGED;
-    gtid_pos_str.length= 0;
+    gtid_pos_str= null_lex_str;
-    gtid_pos_str.str= NULL;
     use_gtid_opt= LEX_GTID_UNCHANGED;
   }
 };
@@ -1021,9 +1023,6 @@ struct st_sp_chistics
   enum enum_sp_data_access daccess;
 };
 
-extern const LEX_STRING null_lex_str;
-extern const LEX_STRING empty_lex_str;
-
 struct st_trg_chistics
 {
   enum trg_action_time_type action_time;
@@ -1035,9 +1034,6 @@ extern sys_var *trg_new_row_fake_var;
 enum xa_option_words {XA_NONE, XA_JOIN, XA_RESUME, XA_ONE_PHASE,
                       XA_SUSPEND, XA_FOR_MIGRATE};
 
-extern const LEX_STRING null_lex_str;
-extern const LEX_STRING empty_lex_str;
-
 class Sroutine_hash_entry;
 
 /*

sql/sql_parse.cc

@@ -1748,8 +1748,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     else
 #endif
     {
-      thd->lex->relay_log_connection_name.str= (char*) "";
+      thd->lex->relay_log_connection_name= empty_lex_str;
-      thd->lex->relay_log_connection_name.length= 0;
       if (reload_acl_and_cache(thd, options, (TABLE_LIST*) 0, &not_used))
         break;
     }
@@ -6721,7 +6720,7 @@ void create_select_for_variable(const char *var_name)
 {
   THD *thd;
   LEX *lex;
-  LEX_STRING tmp, null_lex_string;
+  LEX_STRING tmp;
   Item *var;
   char buff[MAX_SYS_VAR_LENGTH*2+4+8], *end;
   DBUG_ENTER("create_select_for_variable");
@@ -6732,12 +6731,11 @@ void create_select_for_variable(const char *var_name)
   lex->sql_command= SQLCOM_SELECT;
   tmp.str= (char*) var_name;
   tmp.length=strlen(var_name);
-  bzero((char*) &null_lex_string.str, sizeof(null_lex_string));
   /*
     We set the name of Item to @@session.var_name because that then is used
     as the column name in the output.
   */
-  if ((var= get_system_var(thd, OPT_SESSION, tmp, null_lex_string)))
+  if ((var= get_system_var(thd, OPT_SESSION, tmp, null_lex_str)))
   {
     end= strxmov(buff, "@@session.", var_name, NullS);
     var->set_name(buff, end-buff, system_charset_info);
@@ -8762,8 +8760,7 @@ LEX_USER *create_definer(THD *thd, LEX_STRING *user_name, LEX_STRING *host_name)
 
   definer->user= *user_name;
   definer->host= *host_name;
-  definer->password.str= NULL;
+  definer->password= null_lex_str;
-  definer->password.length= 0;
 
   return definer;
 }

sql/sql_yacc.yy

@@ -2374,8 +2374,7 @@ create:
             lex->query_tables->open_strategy= TABLE_LIST::OPEN_STUB;
             lex->create_info.options= ($1 | $2 | $4);
             lex->create_info.default_table_charset= NULL;
-            lex->name.str= 0;
+            lex->name= null_lex_str;
-            lex->name.length= 0;
             lex->create_last_non_select_table= lex->last_table();
           }
           create_body
@@ -7029,8 +7028,7 @@ string_list:
 alter:
           ALTER
           {
-            Lex->name.str= 0;
+            Lex->name= null_lex_str;
-            Lex->name.length= 0;
             Lex->sql_command= SQLCOM_ALTER_TABLE;
             Lex->duplicates= DUP_ERROR; 
             Lex->col_list.empty();
@@ -7247,7 +7245,7 @@ opt_ev_sql_stmt:
         ;
 
 ident_or_empty:
-          /* empty */ { $$.str= 0; $$.length= 0; }
+          /* empty */ { $$= null_lex_str; }
         | ident { $$= $1; }
         ;
 
@@ -12892,8 +12890,7 @@ flush_option:
         | LOGS_SYM
           {
             Lex->type|= REFRESH_LOG;
-            Lex->relay_log_connection_name.str= (char*) "";
+            Lex->relay_log_connection_name= empty_lex_str;
-            Lex->relay_log_connection_name.length= 0;
           }
         | STATUS_SYM
           { Lex->type|= REFRESH_STATUS; }