Bug#42733: Type-punning warnings when compiling MySQL --

            strict aliasing violations.

One somewhat major source of strict-aliasing violations and
related warnings is the SQL_LIST structure. For example,
consider its member function `link_in_list` which takes
a pointer to pointer of type T (any type) as a pointer to
pointer to unsigned char. Dereferencing this pointer, which
is done to reset the next field, violates strict-aliasing
rules and might cause problems for surrounding code that
uses the next field of the object being added to the list.

The solution is to use templates to parametrize the SQL_LIST
structure in order to deference the pointers with compatible
types. As a side bonus, it becomes possible to remove quite
a few casts related to acessing data members of SQL_LIST.

sql/handler.h:
  Use the appropriate template type argument.
sql/item.cc:
  Remove now-unnecessary cast.
sql/item_subselect.cc:
  Remove now-unnecessary casts.
sql/item_sum.cc:
  Use the appropriate template type argument.
  Remove now-unnecessary cast.
sql/mysql_priv.h:
  Move SQL_LIST structure to sql_list.h
  Use the appropriate template type argument.
sql/sp.cc:
  Remove now-unnecessary casts.
sql/sql_delete.cc:
  Use the appropriate template type argument.
  Remove now-unnecessary casts.
sql/sql_derived.cc:
  Remove now-unnecessary casts.
sql/sql_lex.cc:
  Remove now-unnecessary casts.
sql/sql_lex.h:
  SQL_LIST now takes a template type argument which must
  match the type of the elements of the list. Use forward
  declaration when the type is not available, it is used
  in pointers anyway.
sql/sql_list.h:
  Rename SQL_LIST to SQL_I_List. The template parameter is
  the type of object that is stored in the list.
sql/sql_olap.cc:
  Remove now-unnecessary casts.
sql/sql_parse.cc:
  Remove now-unnecessary casts.
sql/sql_prepare.cc:
  Remove now-unnecessary casts.
sql/sql_select.cc:
  Remove now-unnecessary casts.
sql/sql_show.cc:
  Remove now-unnecessary casts.
sql/sql_table.cc:
  Remove now-unnecessary casts.
sql/sql_trigger.cc:
  Remove now-unnecessary casts.
sql/sql_union.cc:
  Remove now-unnecessary casts.
sql/sql_update.cc:
  Remove now-unnecessary casts.
sql/sql_view.cc:
  Remove now-unnecessary casts.
sql/sql_yacc.yy:
  Remove now-unnecessary casts.
storage/myisammrg/ha_myisammrg.cc:
  Remove now-unnecessary casts.

1 files changed, 2 insertions, 45 deletions

diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index 44694c59447..88f3763ef50 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -641,49 +641,6 @@ enum enum_check_fields
   CHECK_FIELD_ERROR_FOR_NULL
 };
 
-                                  
-/** Struct to handle simple linked lists. */
-typedef struct st_sql_list {
-  uint elements;
-  uchar *first;
-  uchar **next;
-
-  st_sql_list() {}                              /* Remove gcc warning */
-  inline void empty()
-  {
-    elements=0;
-    first=0;
-    next= &first;
-  }
-  inline void link_in_list(uchar *element,uchar **next_ptr)
-  {
-    elements++;
-    (*next)=element;
-    next= next_ptr;
-    *next=0;
-  }
-  inline void save_and_clear(struct st_sql_list *save)
-  {
-    *save= *this;
-    empty();
-  }
-  inline void push_front(struct st_sql_list *save)
-  {
-    *save->next= first;				/* link current list last */
-    first= save->first;
-    elements+= save->elements;
-  }
-  inline void push_back(struct st_sql_list *save)
-  {
-    if (save->first)
-    {
-      *next= save->first;
-      next= save->next;
-      elements+= save->elements;
-    }
-  }
-} SQL_LIST;
-
 #if defined(MYSQL_DYNAMIC_PLUGIN) && defined(_WIN32)
 extern "C" THD *_current_thd_noinline();
 #define _current_thd() _current_thd_noinline()
@@ -1262,7 +1219,7 @@ int check_that_all_fields_are_given_values(THD *thd, TABLE *entry,
 void prepare_triggers_for_insert_stmt(TABLE *table);
 int mysql_prepare_delete(THD *thd, TABLE_LIST *table_list, Item **conds);
 bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
-                  SQL_LIST *order, ha_rows rows, ulonglong options,
+                  SQL_I_List<ORDER> *order, ha_rows rows, ulonglong options,
                   bool reset_auto_increment);
 bool mysql_truncate(THD *thd, TABLE_LIST *table_list, bool dont_send_ok);
 bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create);
@@ -1462,7 +1419,7 @@ Create_field * new_create_field(THD *thd, char *field_name, enum_field_types typ
 				List<String> *interval_list, CHARSET_INFO *cs,
 				uint uint_geom_type);
 void store_position_for_column(const char *name);
-bool add_to_list(THD *thd, SQL_LIST &list,Item *group,bool asc);
+bool add_to_list(THD *thd, SQL_I_List<ORDER> &list, Item *group,bool asc);
 bool push_new_name_resolution_context(THD *thd,
                                       TABLE_LIST *left_op,
                                       TABLE_LIST *right_op);