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)

2 files changed, 11 insertions, 12 deletions

diff --git a/storage/oqgraph/ha_oqgraph.cc b/storage/oqgraph/ha_oqgraph.cc
index 2380ab8157e..4b858d468f5 100644
--- a/storage/oqgraph/ha_oqgraph.cc
+++ b/storage/oqgraph/ha_oqgraph.cc
@@ -297,7 +297,7 @@ int ha_oqgraph::oqgraph_check_table_structure (TABLE *table_arg)
 
   Field **field= table_arg->field;
   for (i= 0; *field && skel[i].colname; i++, field++) {
-    DBUG_PRINT( "oq-debug", ("Column %d: name='%s', expected '%s'; type=%d, expected %d.", i, (*field)->field_name, skel[i].colname, (*field)->type(), skel[i].coltype));
+    DBUG_PRINT( "oq-debug", ("Column %d: name='%s', expected '%s'; type=%d, expected %d.", i, (*field)->field_name.str, skel[i].colname, (*field)->type(), skel[i].coltype));
     bool badColumn = false;
     bool isLatchColumn = strcmp(skel[i].colname, "latch")==0;
     bool isStringLatch = true;
@@ -346,7 +346,7 @@ int ha_oqgraph::oqgraph_check_table_structure (TABLE *table_arg)
       push_warning_printf( current_thd, Sql_condition::WARN_LEVEL_WARN, HA_WRONG_CREATE_OPTION, "Column %d must be NULL.", i);
     }
     /* Check the column name */
-    if (!badColumn) if (strcmp(skel[i].colname,(*field)->field_name)) {
+    if (!badColumn) if (strcmp(skel[i].colname,(*field)->field_name.str)) {
       badColumn = true;
       push_warning_printf( current_thd, Sql_condition::WARN_LEVEL_WARN, HA_WRONG_CREATE_OPTION, "Column %d must be named '%s'.", i, skel[i].colname);
     }
@@ -577,11 +577,10 @@ int ha_oqgraph::open(const char *name, int mode, uint test_if_locked)
   size_t tlen= strlen(options->table_name);
   size_t plen= (int)(p - name) + tlen + 1;
 
-  share->path.str= (char*)alloc_root(&share->mem_root, plen + 1); // MDEV-5996 space for trailing zero
-  // it seems there was a misunderstanding of why there is a separate length field in the String object
-  strmov(strnmov(share->path.str, name, (int)(p - name) + 1), options->table_name);
-
-  share->path.str[plen] = 0; // MDEV-5996 Make sure the pointer is zero terminated.  I really think this needs refactoring, soon...
+  share->path.str= (char*)alloc_root(&share->mem_root, plen + 1);
+  strmov(strnmov((char*) share->path.str, name, (int)(p - name) + 1),
+         options->table_name);
+  DBUG_ASSERT(strlen(share->path.str) == plen);
   share->normalized_path.str= share->path.str;
   share->path.length= share->normalized_path.length= plen;
 
@@ -655,7 +654,7 @@ int ha_oqgraph::open(const char *name, int mode, uint test_if_locked)
 
   for (Field **field= edges->field; *field; ++field)
   {
-    if (strcmp(options->origid, (*field)->field_name))
+    if (strcmp(options->origid, (*field)->field_name.str))
       continue;
     if ((*field)->cmp_type() != INT_RESULT ||
         !((*field)->flags & NOT_NULL_FLAG))
@@ -680,7 +679,7 @@ int ha_oqgraph::open(const char *name, int mode, uint test_if_locked)
 
   for (Field **field= edges->field; *field; ++field)
   {
-    if (strcmp(options->destid, (*field)->field_name))
+    if (strcmp(options->destid, (*field)->field_name.str))
       continue;
     if ((*field)->type() != origid->type() ||
         !((*field)->flags & NOT_NULL_FLAG))
@@ -703,7 +702,7 @@ int ha_oqgraph::open(const char *name, int mode, uint test_if_locked)
   }
 
   // Make sure origid column != destid column
-  if (strcmp( origid->field_name, destid->field_name)==0) {
+  if (strcmp( origid->field_name.str, destid->field_name.str)==0) {
     fprint_error("Invalid OQGRAPH backing store ('%s.destid' attribute set to same column as origid attribute)", p+1, options->table_name);
     closefrm(edges);
     free_table_share(share);
@@ -712,7 +711,7 @@ int ha_oqgraph::open(const char *name, int mode, uint test_if_locked)
 
   for (Field **field= edges->field; options->weight && *field; ++field)
   {
-    if (strcmp(options->weight, (*field)->field_name))
+    if (strcmp(options->weight, (*field)->field_name.str))
       continue;
     if ((*field)->result_type() != REAL_RESULT ||
         !((*field)->flags & NOT_NULL_FLAG))
diff --git a/storage/oqgraph/ha_oqgraph.h b/storage/oqgraph/ha_oqgraph.h
index ad0cdd61256..f06db8bbf14 100644
--- a/storage/oqgraph/ha_oqgraph.h
+++ b/storage/oqgraph/ha_oqgraph.h
@@ -118,7 +118,7 @@ public:
   virtual const char *table_type() const { return hton_name(ht)->str; }
 #endif
 
-  my_bool register_query_cache_table(THD *thd, char *table_key,
+  my_bool register_query_cache_table(THD *thd, const char *table_key,
                                      uint key_length,
                                      qc_engine_callback
                                      *engine_callback,