Changing field::field_name and Item::name to LEX_CSTRING

Benefits of this patch:
- Removed a lot of calls to strlen(), especially for field_string
- Strings generated by parser are now const strings, less chance of
  accidently changing a string
- Removed a lot of calls with LEX_STRING as parameter (changed to pointer)
- More uniform code
- Item::name_length was not kept up to date. Now fixed
- Several bugs found and fixed (Access to null pointers,
  access of freed memory, wrong arguments to printf like functions)
- Removed a lot of casts from (const char*) to (char*)

Changes:
- This caused some ABI changes
  - lex_string_set now uses LEX_CSTRING
  - Some fucntions are now taking const char* instead of char*
- Create_field::change and after changed to LEX_CSTRING
- handler::connect_string, comment and engine_name() changed to LEX_CSTRING
- Checked printf() related calls to find bugs. Found and fixed several
  errors in old code.
- A lot of changes from LEX_STRING to LEX_CSTRING, especially related to
  parsing and events.
- Some changes from LEX_STRING and LEX_STRING & to LEX_CSTRING*
- Some changes for char* to const char*
- Added printf argument checking for my_snprintf()
- Introduced null_clex_str, star_clex_string, temp_lex_str to simplify
  code
- Added item_empty_name and item_used_name to be able to distingush between
  items that was given an empty name and items that was not given a name
  This is used in sql_yacc.yy to know when to give an item a name.
- select table_name."*' is not anymore same as table_name.*
- removed not used function Item::rename()
- Added comparision of item->name_length before some calls to
  my_strcasecmp() to speed up comparison
- Moved Item_sp_variable::make_field() from item.h to item.cc
- Some minimal code changes to avoid copying to const char *
- Fixed wrong error message in wsrep_mysql_parse()
- Fixed wrong code in find_field_in_natural_join() where real_item() was
  set when it shouldn't
- ER_ERROR_ON_RENAME was used with extra arguments.
- Removed some (wrong) ER_OUTOFMEMORY, as alloc_root will already
  give the error.

TODO:
- Check possible unsafe casts in plugin/auth_examples/qa_auth_interface.c
- Change code to not modify LEX_CSTRING for database name
  (as part of lower_case_table_names)

1 files changed, 9 insertions, 6 deletions

diff --git a/sql/events.h b/sql/events.h
index 368aa9a05d5..4b4505b6a02 100644
--- a/sql/events.h
+++ b/sql/events.h
@@ -36,7 +36,7 @@ extern PSI_stage_info stage_waiting_on_empty_queue;
 extern PSI_stage_info stage_waiting_for_next_activation;
 extern PSI_stage_info stage_waiting_for_scheduler_to_stop;
 
-#include "sql_string.h"                         /* LEX_STRING */
+#include "sql_string.h"                         /* LEX_CSTRING */
 #include "my_time.h"                            /* interval_type */
 
 class Event_db_repository;
@@ -48,7 +48,8 @@ class THD;
 typedef class Item COND;
 
 int
-sortcmp_lex_string(LEX_STRING s, LEX_STRING t, CHARSET_INFO *cs);
+sortcmp_lex_string(const LEX_CSTRING *s, const LEX_CSTRING *t,
+                   const CHARSET_INFO *cs);
 
 /**
   @brief A facade to the functionality of the Event Scheduler.
@@ -109,16 +110,18 @@ public:
 
   static bool
   update_event(THD *thd, Event_parse_data *parse_data,
-               LEX_STRING *new_dbname, LEX_STRING *new_name);
+               LEX_CSTRING *new_dbname, LEX_CSTRING *new_name);
 
   static bool
-  drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists);
+  drop_event(THD *thd, const LEX_CSTRING *dbname, const LEX_CSTRING *name,
+             bool if_exists);
 
   static void
-  drop_schema_events(THD *thd, char *db);
+  drop_schema_events(THD *thd, const char *db);
 
   static bool
-  show_create_event(THD *thd, LEX_STRING dbname, LEX_STRING name);
+  show_create_event(THD *thd, const LEX_CSTRING *dbname,
+                    const LEX_CSTRING *name);
 
   /* Needed for both SHOW CREATE EVENT and INFORMATION_SCHEMA */
   static int