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.

1 files changed, 13 insertions, 10 deletions

diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 54eefa22a59..fb011f05f08 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -587,8 +587,8 @@ public:
   st_lex *parent_lex;
   enum olap_type olap;
   /* FROM clause - points to the beginning of the TABLE_LIST::next_local list. */
-  SQL_LIST	      table_list;
-  SQL_LIST	      group_list; /* GROUP BY clause. */
+  SQL_I_List<TABLE_LIST>  table_list;
+  SQL_I_List<ORDER>       group_list; /* GROUP BY clause. */
   List<Item>          item_list;  /* list of fields & expressions */
   List<String>        interval_list;
   bool	              is_item_list_lookup;
@@ -610,8 +610,8 @@ public:
   TABLE_LIST *leaf_tables;
   const char *type;               /* type of select for EXPLAIN          */
 
-  SQL_LIST order_list;                /* ORDER clause */
-  SQL_LIST *gorder_list;
+  SQL_I_List<ORDER> order_list;   /* ORDER clause */
+  SQL_I_List<ORDER> *gorder_list;
   Item *select_limit, *offset_limit;  /* LIMIT clause parameters */
   // Arrays of pointers to top elements of all_fields list
   Item **ref_pointer_array;
@@ -774,7 +774,7 @@ public:
   {
     order_list.elements= 0;
     order_list.first= 0;
-    order_list.next= (uchar**) &order_list.first;
+    order_list.next= &order_list.first;
   }
   /*
     This method created for reiniting LEX in mysql_admin_table() and can be
@@ -953,6 +953,8 @@ enum xa_option_words {XA_NONE, XA_JOIN, XA_RESUME, XA_ONE_PHASE,
                       XA_SUSPEND, XA_FOR_MIGRATE};
 
 
+struct Sroutine_hash_entry;
+
 /*
   Class representing list of all tables used by statement.
   It also contains information about stored functions used by statement
@@ -993,9 +995,9 @@ public:
     We use these two members for restoring of 'sroutines_list' to the state
     in which it was right after query parsing.
   */
-  SQL_LIST sroutines_list;
-  uchar    **sroutines_list_own_last;
-  uint     sroutines_list_own_elements;
+  SQL_I_List<Sroutine_hash_entry> sroutines_list;
+  Sroutine_hash_entry **sroutines_list_own_last;
+  uint sroutines_list_own_elements;
 
   /*
     These constructor and destructor serve for creation/destruction
@@ -1599,7 +1601,8 @@ typedef struct st_lex : public Query_tables_list
   */
   List<Name_resolution_context> context_stack;
 
-  SQL_LIST	      proc_list, auxiliary_table_list, save_list;
+  SQL_I_List<ORDER> proc_list;
+  SQL_I_List<TABLE_LIST> auxiliary_table_list, save_list;
   Create_field	      *last_field;
   Item_sum *in_sum_func;
   udf_func udf;
@@ -1721,7 +1724,7 @@ typedef struct st_lex : public Query_tables_list
     fields to TABLE object at table open (altough for latter pointer to table
     being opened is probably enough).
   */
-  SQL_LIST trg_table_fields;
+  SQL_I_List<Item_trigger_field> trg_table_fields;
 
   /*
     stmt_definition_begin is intended to point to the next word after