MDEV-12179: Per-engine mysql.gtid_slave_pos table

Intermediate commit.

Fix compilation failure with different my_atomic implementation.

The my_atomic_loadptr* takes void ** as first argument, so variables
updated with it needs to be void * (it is not legal C to cast
some_type ** to void **).

4 files changed, 20 insertions, 12 deletions

diff --git a/sql/rpl_gtid.cc b/sql/rpl_gtid.cc
index a4a774a0200..b1b65119d0b 100644
--- a/sql/rpl_gtid.cc
+++ b/sql/rpl_gtid.cc
@@ -258,7 +258,7 @@ rpl_slave_state::rpl_slave_state()
 
 rpl_slave_state::~rpl_slave_state()
 {
-  free_gtid_pos_tables(gtid_pos_tables);
+  free_gtid_pos_tables((struct gtid_pos_table *)gtid_pos_tables);
   truncate_hash();
   my_hash_free(&hash);
   delete_dynamic(&gtid_sort_array);
@@ -484,7 +484,8 @@ rpl_slave_state::select_gtid_pos_table(THD *thd, LEX_STRING *out_tablename)
     See comments on rpl_slave_state::gtid_pos_tables for rules around proper
     access to the list.
   */
-  list= my_atomic_loadptr_explicit(&gtid_pos_tables, MY_MEMORY_ORDER_ACQUIRE);
+  list= (struct gtid_pos_table *)
+    my_atomic_loadptr_explicit(&gtid_pos_tables, MY_MEMORY_ORDER_ACQUIRE);
 
   Ha_trx_info *ha_info;
   uint count = 0;
@@ -545,8 +546,8 @@ rpl_slave_state::select_gtid_pos_table(THD *thd, LEX_STRING *out_tablename)
     already active in the transaction, or if there is no current transaction
     engines available, we return the default gtid_slave_pos table.
   */
-  default_entry= my_atomic_loadptr_explicit(&default_gtid_pos_table,
-                                            MY_MEMORY_ORDER_ACQUIRE);
+  default_entry= (struct gtid_pos_table *)
+    my_atomic_loadptr_explicit(&default_gtid_pos_table, MY_MEMORY_ORDER_ACQUIRE);
   *out_tablename= default_entry->table_name;
   /* Record in status that we failed to find a suitable gtid_pos table. */
   if (count > 0)
@@ -1268,7 +1269,7 @@ rpl_slave_state::set_gtid_pos_tables_list(rpl_slave_state::gtid_pos_table *new_l
   gtid_pos_table *old_list;
 
   mysql_mutex_assert_owner(&LOCK_slave_state);
-  old_list= gtid_pos_tables;
+  old_list= (struct gtid_pos_table *)gtid_pos_tables;
   my_atomic_storeptr_explicit(&gtid_pos_tables, new_list, MY_MEMORY_ORDER_RELEASE);
   my_atomic_storeptr_explicit(&default_gtid_pos_table, default_entry,
                               MY_MEMORY_ORDER_RELEASE);
@@ -1280,7 +1281,7 @@ void
 rpl_slave_state::add_gtid_pos_table(rpl_slave_state::gtid_pos_table *entry)
 {
   mysql_mutex_assert_owner(&LOCK_slave_state);
-  entry->next= gtid_pos_tables;
+  entry->next= (struct gtid_pos_table *)gtid_pos_tables;
   my_atomic_storeptr_explicit(&gtid_pos_tables, entry, MY_MEMORY_ORDER_RELEASE);
 }
 
diff --git a/sql/rpl_gtid.h b/sql/rpl_gtid.h
index 4ff1ca563b8..452f3676704 100644
--- a/sql/rpl_gtid.h
+++ b/sql/rpl_gtid.h
@@ -206,10 +206,13 @@ struct rpl_slave_state
     The list can be read without lock by an SQL driver thread or worker thread
     by reading the gtid_pos_tables pointer atomically with acquire semantics,
     to ensure that it will see the correct next pointer of a new head element.
+
+    The type is struct gtid_pos_table *, but needs to be void * to allow using
+    my_atomic operations without violating C strict aliasing semantics.
   */
-  struct gtid_pos_table *gtid_pos_tables;
+  void * volatile gtid_pos_tables;
   /* The default entry in gtid_pos_tables, mysql.gtid_slave_pos. */
-  struct gtid_pos_table *default_gtid_pos_table;
+  void * volatile default_gtid_pos_table;
   bool loaded;
 
   rpl_slave_state();
diff --git a/sql/rpl_rli.cc b/sql/rpl_rli.cc
index 59138a23daf..63179f5d8e9 100644
--- a/sql/rpl_rli.cc
+++ b/sql/rpl_rli.cc
@@ -1973,7 +1973,8 @@ find_gtid_slave_pos_tables(THD *thd)
     */
     rpl_slave_state::gtid_pos_table *old_entry, *new_entry, **next_ptr_ptr;
 
-    old_entry= rpl_global_gtid_slave_state->gtid_pos_tables;
+    old_entry= (rpl_slave_state::gtid_pos_table *)
+      rpl_global_gtid_slave_state->gtid_pos_tables;
     while (old_entry)
     {
       new_entry= cb_data.table_list;
@@ -1995,7 +1996,8 @@ find_gtid_slave_pos_tables(THD *thd)
     while (new_entry)
     {
       /* Check if we already have a table with this storage engine. */
-      old_entry= rpl_global_gtid_slave_state->gtid_pos_tables;
+      old_entry= (rpl_slave_state::gtid_pos_table *)
+        rpl_global_gtid_slave_state->gtid_pos_tables;
       while (old_entry)
       {
         if (new_entry->table_hton == old_entry->table_hton)
diff --git a/sql/slave.cc b/sql/slave.cc
index a892bba82c9..ffce356c2ec 100644
--- a/sql/slave.cc
+++ b/sql/slave.cc
@@ -383,7 +383,8 @@ handle_gtid_pos_auto_create_request(THD *thd, void *hton)
 
   /* Find the entry for the table to auto-create. */
   mysql_mutex_lock(&rpl_global_gtid_slave_state->LOCK_slave_state);
-  entry= rpl_global_gtid_slave_state->gtid_pos_tables;
+  entry= (rpl_slave_state::gtid_pos_table *)
+    rpl_global_gtid_slave_state->gtid_pos_tables;
   while (entry)
   {
     if (entry->table_hton == hton &&
@@ -419,7 +420,8 @@ handle_gtid_pos_auto_create_request(THD *thd, void *hton)
 
   /* Now enable the entry for the auto-created table. */
   mysql_mutex_lock(&rpl_global_gtid_slave_state->LOCK_slave_state);
-  entry= rpl_global_gtid_slave_state->gtid_pos_tables;
+  entry= (rpl_slave_state::gtid_pos_table *)
+    rpl_global_gtid_slave_state->gtid_pos_tables;
   while (entry)
   {
     if (entry->table_hton == hton &&